The influence of carbohydrate-protein co-ingestion following endurance exercise on myofibrillar and mitochondrial protein synthesis

Common questions and misconceptions about protein supplementation: what does the scientific evidence really show?

Protein supplementation often refers to increasing the intake of this particular macronutrient through dietary supplements in the form of powders, ready-to-drink shakes, and bars. The primary purpose of protein supplementation is to augment dietary protein intake, aiding individuals in meeting their protein requirements, especially when it may be challenging to do so through regular food (i.e. chicken, beef, fish, pork, etc.) sources alone. A large body of evidence shows that protein has an important role in exercising and sedentary individuals. A PubMed search of "protein and exercise performance" reveals thousands of publications. Despite the considerable volume of evidence, it is somewhat surprising that several persistent questions and misconceptions about protein exist. The following are addressed: 1) Is protein harmful to your kidneys? 2) Does consuming "excess" protein increase fat mass? 3) Can dietary protein have a harmful effect on bone health? 4) Can vegans and vegetarians consume enough protein to support training adaptations? 5) Is cheese or peanut butter a good protein source? 6) Does consuming meat (i.e., animal protein) cause unfavorable health outcomes? 7) Do you need protein if you are not physically active? 8) Do you need to consume protein ≤ 1 hour following resistance training sessions to create an anabolic environment in skeletal muscle? 9) Do endurance athletes need additional protein? 10) Does one need protein supplements to meet the daily requirements of exercise-trained individuals? 11) Is there a limit to how much protein one can consume in a single meal? To address these questions, we have conducted a thorough scientific assessment of the literature concerning protein supplementation.

Protein Supplementation Increases Adaptations to Low-Volume, Intra-Session Concurrent Training in Untrained Healthy Adults: A Double-Blind, Placebo-Controlled, Randomized Trial

Combined endurance and resistance training, also known as "concurrent training", is a common practice in exercise routines. While concurrent training offers the benefit of targeting both cardiovascular and muscular fitness, it imposes greater physiological demands on the body compared to performing each modality in isolation. Increased protein consumption has been suggested to support adaptations to concurrent training. However, the impact of protein supplementation on responses to low-volume concurrent training is still unclear. Forty-four untrained, healthy individuals (27 ± 6 years) performed two sessions/week of low-volume high-intensity interval training on cycle ergometers followed by five machine-based resistance training exercises for 8 weeks. Volunteers randomly received (double-blinded) 40 g of whey-based protein (PRO group) or an isocaloric placebo (maltodextrin, PLA group) after each session. Maximal oxygen consumption (VO2max) and overall fitness scores (computed from volunteers' VO2max and one-repetition maximum scores, 1-RM) significantly increased in both groups. The PRO group showed significantly improved 1-RM in all major muscle groups, while the PLA group only improved 1-RM in chest and upper back muscles. Improvements in 1-RM in leg muscles were significantly greater in the PRO group versus the PLA group. In conclusion, our results indicate that adaptations to low-volume concurrent training, particularly leg muscle strength, can be improved with targeted post-exercise protein supplementation in untrained healthy individuals.

Association between changes in lean mass, muscle strength, endurance, and power following resistance or concurrent training with differing high protein diets in resistance-trained young males

Background

We assessed the relationship of changes in upper and lower body lean mass with muscle strength, endurance and power responses following two high protein diets (1.6 or 3.2 g.kg-1.d-1) during 16 weeks of either concurrent training (CT) or resistance training (RT) in resistance-trained young males.

Methods

Forty-eight resistance-trained young males (age: 26 ± 6 yr., body mass index: 25.6 ± 2.9 kg.m-2) performed 16 weeks (four sessions·wk.-1) of CT or RT with either 1.6 g.kg-1.d-1 protein (CT + 1.6; n = 12; RT + 1.6; n = 12) or 3.2 g.kg-1.d-1 protein (CT + 3.2; n = 12; RT + 3.2; n = 12). Relationships between upper (left arm + right arm + trunk lean mass) and lower body (left leg + right leg lean mass) lean mass changes with changes in muscle performance were assessed using Pearson's correlation coefficients.

Results

For upper body, non-significant weak positive relationships were observed between change in upper body lean mass and change in pull-up (r = 0.183, p = 0.234), absolute chest press strength (r = 0.159, p = 0.302), chest press endurance (r = 0.041, p = 0.792), and relative chest press strength (r = 0.097, p = 0.529) while non-significant weak negative relationships were observed for changes in absolute upper body power (r = -0.236, p = 0.123) and relative upper body power (r = -0.203, p = 0.185). For lower body, non-significant weak positive relationships were observed between the change in lower body lean mass with change in vertical jump (r = 0.145, p = 0.346), absolute lower body power (r = 0.109, p = 0.480), absolute leg press strength (r = 0.073, p = 0.638), leg press endurance (r < 0.001, p = 0.998), relative leg press strength (r = 0.089, p = 0.564), and relative lower body power (r = 0.150, p = 0.332).

Conclusion

Changes in muscle strength, endurance and power adaptation responses following 16 weeks of either CT or RT with different high protein intakes were not associated with changes in lean mass in resistance-trained young males. These findings indicate that muscle hypertrophy has a small, or negligible, contributory role in promoting functional adaptations with RT or CT, at least over a 16-week period.

Age-related changes in human skeletal muscle transcriptome and proteome are more affected by chronic inflammation and physical inactivity than primary aging

Evaluation of the influence of primary and secondary aging on the manifestation of molecular and cellular hallmarks of aging is a challenging and currently unresolved issue. Our study represents the first demonstration of the distinct role of primary aging and chronic inflammation/physical inactivity - the most important drivers of secondary aging, in the regulation of transcriptomic and proteomic profiles in human skeletal muscle. To achieve this purpose, young healthy people (n = 15), young (n = 8) and older (n = 37) patients with knee/hip osteoarthritis, a model to study the effect of long-term inactivity and chronic inflammation on the vastus lateralis muscle, were included in the study. It was revealed that widespread and substantial age-related changes in gene expression in older patients relative to young healthy people (~4000 genes regulating mitochondrial function, proteostasis, cell membrane, secretory and immune response) were related to the long-term physical inactivity and chronic inflammation rather than primary aging. Primary aging contributed mainly to the regulation of genes (~200) encoding nuclear proteins (regulators of DNA repair, RNA processing, and transcription), mitochondrial proteins (genes encoding respiratory enzymes, mitochondrial complex assembly factors, regulators of cristae formation and mitochondrial reactive oxygen species production), as well as regulators of proteostasis. It was found that proteins associated with aging were regulated mainly at the post-transcriptional level. The set of putative primary aging genes and their potential transcriptional regulators can be used as a resource for further targeted studies investigating the role of individual genes and related transcription factors in the emergence of a senescent cell phenotype.

Transcriptomic Analysis of Human Skeletal Muscle in Response to Aerobic Exercise and Protein Intake

This study aimed to provide a more comprehensive molecular insight into the effects of aerobic exercise (AE), protein intake (PI), and AE combined with PI on human skeletal muscle by comparing their transcriptomic profiles. Fourteen published datasets obtained from the Gene Expression Omnibus (GEO) database were used. The hub genes were identified in response to acute AE (ACTB, IL6), training AE (UBB, COL1A1), PI (EZH2), acute AE combined with PI (DDIT3), and training AE combined with PI (MYC). Both FOS and MYC were upregulated in response to acute AE, and they were, respectively, downregulated by higher PI and a combination of AE and PI. COL1A1 was upregulated by training AE but was downregulated by higher PI. Results from the gene set enrichment analysis (p < 0.05 and FDR < 25%) showed that AE and PI delivered their impacts on human skeletal muscle in analogous pathways, including aerobic respiration, mitochondrial complexes, extracellular matrix (ECM) remodeling, metabolic process, and immune/inflammatory responses, whereas, PI may attenuate the response of immune/inflammation and ECM remodeling which would be promoted by AE, irrespective of its types. Compared to PI alone, acute AE combined with PI would further promote protein turnover and synthesis, but suppress skeletal muscle contraction and movement.

Pre-sleep Protein Ingestion Increases Mitochondrial Protein Synthesis Rates During Overnight Recovery from Endurance Exercise: A Randomized Controlled Trial

BACKGROUND

Casein protein ingestion prior to sleep has been shown to increase myofibrillar protein synthesis rates during overnight sleep. It remains to be assessed whether pre-sleep protein ingestion can also increase mitochondrial protein synthesis rates. Though it has been suggested that casein protein may be preferred as a pre-sleep protein source, no study has compared the impact of pre-sleep whey versus casein ingestion on overnight muscle protein synthesis rates.

OBJECTIVE

We aimed to assess the impact of casein and whey protein ingestion prior to sleep on mitochondrial and myofibrillar protein synthesis rates during overnight recovery from a bout of endurance-type exercise.

METHODS

Thirty-six healthy young men performed a single bout of endurance-type exercise in the evening (19:45 h). Thirty minutes prior to sleep (23:30 h), participants ingested 45 g of casein protein, 45 g of whey protein, or a non-caloric placebo. Continuous intravenous L-[ring-13C6]-phenylalanine infusions were applied, with blood and muscle tissue samples being collected to assess overnight mitochondrial and myofibrillar protein synthesis rates.

RESULTS

Pooled protein ingestion resulted in greater mitochondrial (0.087 ± 0.020 vs 0.067 ± 0.016%·h-1, p = 0.005) and myofibrillar (0.060 ± 0.014 vs 0.047 ± 0.011%·h-1, p = 0.012) protein synthesis rates when compared with placebo. Casein and whey protein ingestion did not differ in their capacity to stimulate mitochondrial (0.082 ± 0.019 vs 0.092 ± 0.020%·h-1, p = 0.690) and myofibrillar (0.056 ± 0.009 vs 0.064 ± 0.018%·h-1, p = 0.440) protein synthesis rates.

CONCLUSIONS

Protein ingestion prior to sleep increases both mitochondrial and myofibrillar protein synthesis rates during overnight recovery from exercise. The overnight muscle protein synthetic response to whey and casein protein does not differ.

CLINICAL TRIAL REGISTRATION

NTR7251 .

Protein Supplementation Does Not Maximize Adaptations to Low-Volume High-Intensity Interval Training in Sedentary, Healthy Adults: A Placebo-Controlled Double-Blind Randomized Study

There is ample evidence that specific nutritional strategies can enhance adaptions to resistance and endurance training. However, it is still unclear whether post-session protein supplementation may increase the effects of low-volume high-intensity interval training (LOW-HIIT). We examined the impact of LOW-HIIT combined with protein vs. placebo supplementation on cardiometabolic health indices in sedentary healthy individuals. Forty-seven participants (31.1 ± 8.0 yrs) performed cycle ergometer LOW-HIIT (5−10x1 min at 80−95% maximum heart rate) for eight weeks and randomly received double-blinded 40 g of whey protein (PRO-HIIT, N = 24) or an isocaloric placebo (maltodextrin, PLA-HIIT, N = 23) after each session. The maximum oxygen uptake (VO2max, primary outcome) and several secondary cardiometabolic outcomes were determined pre-/post-intervention. VO2max increased in PRO-HIIT (+2.8 mL/kg/min, p = 0.003) and PLA-HIIT (+3.5 mL/kg/min, p < 0.001). Systolic and diastolic blood pressure decreased in PRO-HIIT (−7/3 mmHg, p < 0.05) and PLA-HIIT (−8/5 mmHg, p < 0.001). Gamma glutamyl transferase (−2 U/L, p = 0.003) decreased in PRO-HIIT and alanine aminotransferase (−3 U/L, p = 0.014) in PLA-HIIT. There were no significant between-group differences in any of the outcome changes. In conclusion, LOW-HIIT improved VO2max and other cardiometabolic markers irrespective of the supplementation condition. Post-session protein supplementation does not seem to provide any additional benefit to LOW-HIIT in improving cardiometabolic health in sedentary healthy individuals.

Evaluating the Effects of Increased Protein Intake on Muscle Strength, Hypertrophy and Power Adaptations with Concurrent Training: A Narrative Review

Concurrent training incorporates dual exercise modalities, typically resistance and aerobic-based exercise, either in a single session or as part of a periodized training program, that can promote muscle strength, mass, power/force and aerobic capacity adaptations for the purposes of sports performance or general health/wellbeing. Despite multiple health and exercise performance-related benefits, diminished muscle hypertrophy, strength and power have been reported with concurrent training compared to resistance training in isolation. Dietary protein is well-established to facilitate skeletal muscle growth, repair and regeneration during recovery from exercise. The degree to which increased protein intake can amplify adaptation responses with resistance exercise, and to a lesser extent aerobic exercise, has been highly studied. In contrast, much less focus has been directed toward the capacity for protein to enhance anabolic and metabolic responses with divergent contractile stimuli inherent to concurrent training and potentially negate interference in muscle strength, power and hypertrophy. This review consolidates available literature investigating increased protein intake on rates of muscle protein synthesis, hypertrophy, strength and force/power adaptations following acute and chronic concurrent training. Acute concurrent exercise studies provide evidence for the significant stimulation of myofibrillar protein synthesis with protein compared to placebo ingestion. High protein intake can also augment increases in lean mass with chronic concurrent training, although these increases do not appear to translate into further improvements in strength adaptations. Similarly, the available evidence indicates protein intake twice the recommended intake and beyond does not rescue decrements in selective aspects of muscle force and power production with concurrent training.

Celebrating the Professional Life of Professor Kevin D. Tipton (1961-2022)

This invited editorial celebrates the distinguished professional life of Professor Kevin D. Tipton, who sadly passed away on January 9, 2022. Professor Tipton made an outstanding contribution to the scientific field of sport nutrition and exercise metabolism over an exceptional 30-year career. He dedicated his academic career to understanding the response of muscle protein metabolism to exercise and nutrition. The impact of his work is far-reaching with application to athletes in terms of promoting training adaptation, recovery, and performance, alongside clinical implications for injury management and healthy aging. Notable scientific contributions included the first in vivo human study to demonstrate the role of orally ingested essential amino acids in stimulating muscle protein synthesis during acute post-exercise recovery. This finding laid the foundation for future studies to interrogate the response of muscle protein synthesis to the ingestion of different protein types. Professor Tipton's work also included investigating the maximally effective dose and timing (regarding exercise) of ingested protein for the stimulation of muscle protein synthesis. Kevin will be remembered fondly by academics, applied scientists, and students across the sport nutrition and exercise metabolism community as a leading researcher in the field, a critical thinker, and an inspirational teacher. His mission was to educate the next generation of exercise scientists by sharing his distinct wealth of knowledge accrued over three decades. Above all else, Kevin was kind, generous (with his time and knowledge), honest, and incredibly social. He was a unique character and will be greatly missed among our community but certainly never forgotten.

The Effects of Dietary Protein Supplementation on Acute Changes in Muscle Protein Synthesis and Longer-Term Changes in Muscle Mass, Strength, and Aerobic Capacity in Response to Concurrent Resistance and Endurance Exercise in Healthy Adults: A Systematic Review

BACKGROUND

Engaging in both resistance and endurance exercise within the same training program, termed 'concurrent exercise training,' is common practice in many athletic disciplines that require a combination of strength and endurance and is recommended by a number of organizations to improve muscular and cardiovascular health and reduce the risk of chronic metabolic disease. Dietary protein ingestion supports skeletal muscle remodeling after exercise by stimulating the synthesis of muscle proteins and can optimize resistance exercise-training mediated increases in skeletal muscle size and strength; however, the effects of protein supplementation on acute and longer-term adaptive responses to concurrent resistance and endurance exercise are unclear.

OBJECTIVES

The purpose of this systematic review is to evaluate the effects of dietary protein supplementation on acute changes in muscle protein synthesis and longer-term changes in muscle mass, strength, and aerobic capacity in responses to concurrent resistance and endurance exercise in healthy adults.

METHODS

A systematic search was conducted in five databases: Scopus, Embase, Medline, PubMed, and Web of Science. Acute and longer-term controlled trials involving concurrent exercise and protein supplementation in healthy adults (ages 18-65 years) were included in this systematic review. Main outcomes of interest were changes in skeletal muscle protein synthesis rates, muscle mass, muscle strength, and whole-body aerobic capacity (i.e., maximal/peak aerobic capacity [VO_2max/peak]). The quality of studies was assessed using the National Institute of Health Quality Assessment for Controlled Intervention Studies.

RESULTS

Four acute studies including 84 trained young males and ten longer-term studies including 167 trained and 391 untrained participants fulfilled the eligibility criteria. All included acute studies demonstrated that protein ingestion enhanced myofibrillar protein synthesis rates, but not mitochondrial protein synthesis rates during post-exercise recovery after an acute bout of concurrent exercise. Of the included longer-term training studies, five out of nine reported that protein supplementation enhanced concurrent training-mediated increases in muscle mass, while five out of nine studies reported that protein supplementation enhanced concurrent training-mediated increases in muscle strength and/or power. In terms of aerobic adaptations, all six included studies reported no effect of protein supplementation on concurrent training-mediated increases in VO_2max/peak.

CONCLUSION

Protein ingestion after an acute bout of concurrent exercise further increases myofibrillar, but not mitochondrial, protein synthesis rates during post-exercise recovery. There is some evidence that protein supplementation during longer-term training further enhances concurrent training-mediated increases in skeletal muscle mass and strength/power, but not whole-body aerobic capacity (i.e., VO_2max/peak).

Muscle Protein Synthesis Responses Following Aerobic-Based Exercise or High-Intensity Interval Training with or Without Protein Ingestion: A Systematic Review

BACKGROUND

Systematic investigation of muscle protein synthesis (MPS) responses with or without protein ingestion has been largely limited to resistance training.

OBJECTIVE

This systematic review determined the capacity for aerobic-based exercise or high-intensity interval training (HIIT) to stimulate post-exercise rates of MPS and whether protein ingestion further significantly increases MPS compared with placebo.

METHODS

Three separate models analysed rates of either mixed, myofibrillar, sarcoplasmic, or mitochondrial protein synthesis (PS) following aerobic-based exercise or HIIT: Model 1 (n = 9 studies), no protein ingestion; Model 2 (n = 7 studies), peri-exercise protein ingestion with no placebo comparison; Model 3 (n = 14 studies), peri-exercise protein ingestion with placebo comparison.

RESULTS

Eight of nine studies and all seven studies in Models 1 and 2, respectively, demonstrated significant post-exercise increases in either mixed or a specific muscle protein pool. Model 3 observed significantly greater MPS responses with protein compared with placebo in either mixed or a specific muscle fraction in 7 of 14 studies. Seven studies showed no difference in MPS between protein and placebo, while three studies reported no significant increases in mitochondrial PS with protein compared with placebo.

CONCLUSION

Most studies reporting significant increases in MPS were confined to mixed and myofibrillar PS that may facilitate power generating capacity of working skeletal muscle with aerobic-based exercise and HIIT. Only three of eight studies demonstrated significant increases in mitochondrial PS post-exercise, with no further benefits of protein ingestion. This lack of change may be explained by the acute analysis window in most studies and apparent latency in exercise-induced stimulation of mitochondrial PS.

Early resistance training-mediated stimulation of daily muscle protein synthetic responses to higher habitual protein intake in middle-aged adults

KEY POINTS

The ingestion of protein potentiates the stimulation of myofibrillar protein synthesis rates after an acute bout of resistance exercise. Protein supplementation (eating above the protein Recommended Dietary Allowance) during resistance training has been shown to maximize lean mass and strength gains in healthy young and older adults. Here, contractile, oxidative, and structural protein synthesis were assessed in skeletal muscle in response to a moderate or higher protein diet during the early adaptive phase of resistance training in middle-aged adults. The stimulation of myofibrillar, mitochondrial or collagen protein synthesis rates during 0-3 weeks of resistance training is not further enhanced by a higher protein diet. These results show that moderate protein diets are sufficient to support the skeletal muscle adaptive response during the early phase of a resistance training programme.

ABSTRACT

Protein ingestion augments muscle protein synthesis (MPS) rates acutely after resistance exercise and can offset age-related loss in muscle mass. Skeletal muscle contains a variety of protein pools, such as myofibrillar (contractile), mitochondrial (substrate oxidation), and collagen (structural support) proteins, and the sensitivity to nutrition and exercise seems to be dependent on the major protein fraction studied. However, it is unknown how free-living conditions with high dietary protein density and habitual resistance exercise mediates muscle protein subfraction synthesis. Therefore, we investigated the effect of moderate (MOD: 1.06 ± 0.22 g kg^-1  day^-1 ) or high (HIGH: 1.55 ± 0.25 g kg^-1  day^-1 ) protein intake on daily MPS rates within the myofibrillar (MyoPS), mitochondrial (MitoPS) and collagen (CPS) protein fractions in middle-aged men and women (n = 20, 47 ± 1 years, BMI 28 ± 1 kg m^-2 ) during the early phase (0-3 weeks) of a dietary counselling-controlled resistance training programme. Participants were loaded with deuterated water, followed by daily maintenance doses throughout the intervention. Muscle biopsies were collected at baseline and after weeks 1, 2 and 3. MyoPS in the HIGH condition remained constant (P = 1.000), but MOD decreased over time (P = 0.023). MitoPS decreased after 0-3 weeks when compared to 0-1 week (P = 0.010) with no effects of protein intake (P = 0.827). A similar decline with no difference between groups (P = 0.323) was also observed for CPS (P = 0.007). Our results demonstrated that additional protein intake above moderate amounts does not potentiate the stimulation of longer-term MPS responses during the early stage of resistance training adaptations in middle-aged adults.

Can High-Intensity Interval Training Promote Skeletal Muscle Anabolism?

Exercise training in combination with optimal nutritional support is an effective strategy to maintain or increase skeletal muscle mass. A single bout of resistance exercise undertaken with adequate protein availability increases rates of muscle protein synthesis and, when repeated over weeks and months, leads to increased muscle fiber size. While resistance-based training is considered the 'gold standard' for promoting muscle hypertrophy, other modes of exercise may be able to promote gains in muscle mass. High-intensity interval training (HIIT) comprises short bouts of exercise at or above the power output/speed that elicits individual maximal aerobic capacity, placing high tensile stress on skeletal muscle, and somewhat resembling the demands of resistance exercise. While HIIT induces rapid increases in skeletal muscle oxidative capacity, the anabolic potential of HIIT for promoting concurrent gains in muscle mass and cardiorespiratory fitness has received less scientific inquiry. In this review, we discuss studies that have determined muscle growth responses after HIIT, with a focus on molecular responses, that provide a rationale for HIIT to be implemented among populations who are susceptible to muscle loss (e.g. middle-aged or older adults) and/or in clinical settings (e.g. pre- or post-surgery).

Effects of whey protein on skeletal muscle microvascular and mitochondrial plasticity following 10 weeks of exercise training in men with type 2 diabetes

Skeletal muscle microvascular dysfunction and mitochondrial rarefaction feature in type 2 diabetes mellitus (T2DM) linked to low tissue glucose disposal rate (GDR). Exercise training and milk protein supplementation independently promote microvascular and metabolic plasticity in muscle associated with improved nutrient delivery, but combined effects are unknown. In a randomised-controlled trial, 24 men (55.6 y, SD 5.7) with T2DM ingested whey protein drinks (protein/carbohydrate/fat: 20/10/3 g; WHEY) or placebo (carbohydrate/fat: 30/3 g; CON) before/after 45 mixed-mode intense exercise sessions over 10 weeks, to study effects on insulin-stimulated (hyperinsulinemic clamp) skeletal-muscle microvascular blood flow (mBF) and perfusion (near-infrared spectroscopy), and histological, genetic, and biochemical markers (biopsy) of microvascular and mitochondrial plasticity. WHEY enhanced insulin-stimulated perfusion (WHEY-CON 5.6%; 90% CI -0.1, 11.3), while mBF was not altered (3.5%; -17.5, 24.5); perfusion, but not mBF, associated (regression) with increased GDR. Exercise training increased mitochondrial (range of means: 40%-90%) and lipid density (20%-30%), enzyme activity (20%-70%), capillary:fibre ratio (∼25%), and lowered systolic (∼4%) and diastolic (4%-5%) blood pressure, but without WHEY effects. WHEY dampened PGC1α -2.9% (90% compatibility interval: -5.7, -0.2) and NOS3 -6.4% (-1.4, -0.2) expression, but other messenger RNA (mRNA) were unclear. Skeletal muscle microvascular and mitochondrial exercise adaptations were not accentuated by whey protein ingestion in men with T2DM. ANZCTR Registration Number: ACTRN12614001197628. Novelty: Chronic whey ingestion in T2DM with exercise altered expression of several mitochondrial and angiogenic mRNA. Whey added no additional benefit to muscle microvascular or mitochondrial adaptations to exercise. Insulin-stimulated perfusion increased with whey but was without impact on glucose disposal.

Six Weeks of Aerobic Exercise in Untrained Men With Overweight/Obesity Improved Training Adaptations, Performance and Body Composition Independent of Oat/Potato or Milk Based Protein-Carbohydrate Drink Supplementation

Background: Protein availability around aerobic exercise might benefit aerobic capacity and body composition in normal weight adults. However, it is unknown if individuals with overweight/obesity elicit similar adaptations or improve other cardiometabolic/health-related markers in response to different types of protein. Thus, our aim was to study the effect of supplementation of two different protein drinks in conjunction with exercise on aerobic capacity, body composition and blood health markers in untrained subjects with overweight or obesity.

Methods: The present study measured training adaptation and health parameters over a 6 week period in untrained men with overweight/obesity (n = 28; BMI 30.4 ± 2.2 kg/m²) ingesting either plant- (Oat/Potato; n = 8) or animal-based (Milk; n = 10) protein-carbohydrate drinks (10 g of protein/serving), or a control carbohydrate drink (n = 10) acutely before and after each training session (average three sessions/week @ 70% HR_max). Pre-post intervention V˙O2peak, muscle biopsies and blood samples were collected, body composition measured (DXA) and two different exercise tests performed. Body weight was controlled with participants remaining weight stable throughout the intervention.

Results: For the groups combined, the training intervention significantly increased V˙O2peak (8%; P < 0.001), performance in a time-to-exhaustion trial (~ 100%; P < 0.001), mitochondrial protein content and enzyme activity (~20–200%). Lean body mass increased (1%; P < 0.01) and fat mass decreased (3%; P < 0.01). No significant effects on fasting blood glucose, insulin, lipids or markers of immune function were observed. There were no significant interactions between drink conditions for training adaptation or blood measurements. For body composition, the Oat/Potato and carbohydrate group decreased leg fat mass significantly more than the Milk group (interaction P < 0.05).

Conclusions: Aerobic capacity and body composition were improved and a number of mitochondrial, glycolytic and oxidative skeletal muscle proteins and enzyme activities were upregulated by a 6 week training intervention. However, none of the parameters for endurance training adaptation were influenced by protein supplementation before and after each training session.

Assessing Overall Exercise Recovery Processes Using Carbohydrate and Carbohydrate-Protein Containing Recovery Beverages

We compared the impact of two different, but commonly consumed, beverages on integrative markers of exercise recovery following a 2 h high intensity interval exercise (i.e., running 70-80% V̇O2 max intervals and interspersed with plyometric jumps). Participants (n = 11 males, n = 6 females) consumed a chocolate flavored dairy milk beverage (CM: 1.2 g carbohydrate/kg BM and 0.4 g protein/kg BM) or a carbohydrate-electrolyte beverage (CEB: isovolumetric with 0.76 g carbohydrate/kg BM) after exercise, in a randomized-crossover design. The recovery beverages were provided in three equal boluses over a 30 min period commencing 1 h post-exercise. Muscle biopsies were performed at 0 h and 2 h in recovery. Venous blood samples, nude BM and total body water were collected before and at 0, 2, and 4 h recovery. Gastrointestinal symptoms and breath hydrogen (H2) were collected before exercise and every 30 min during recovery. The following morning, participants returned for performance assessment. In recovery, breath H2 reached clinical relevance of >10 ppm following consumption of both beverages, in adjunct with high incidence of gastrointestinal symptoms (70%), but modest severity. Blood glucose response was greater on CEB vs. CM (P < 0.01). Insulin response was greater on CM compared with CEB (P < 0.01). Escherichia coli lipopolysaccharide stimulated neutrophil function reduced on both beverages (49%). p-GSK-3β/total-GSK-3β was greater on CM compared with CEB (P = 0.037); however, neither beverage achieved net muscle glycogen re-storage. Phosphorylation of mTOR was greater on CM than CEB (P < 0.001). Fluid retention was lower (P = 0.038) on CEB (74.3%) compared with CM (82.1%). Physiological and performance outcomes on the following day did not differ between trials. Interconnected recovery optimization markers appear to respond differently to the nutrient composition of recovery nutrition, albeit subtly and with individual variation. The present findings expand on recovery nutrition strategies to target functionality and patency of the gastrointestinal tract as a prerequisite to assimilation of recovery nutrition, as well as restoration of immunocompetency.

Effects of Beef Protein Supplementation in Male Elite Triathletes: A Randomized, Controlled, Double-Blind, Cross-Over Study

OBJECTIVE

Beef protein extracts are growing in popularity in recent years due to their purported anabolic effects as well as to their potential benefits on hematological variables. The present randomized, controlled, double-blind, cross-over study aimed to analyze the effects of beef protein supplementation on a group of male elite triathletes (Spanish National Team).

METHODS

Six elite triathletes (age, 21 ± 3 years; VO2max, 71.5 ± 3.0 ml·kg·min-1) were randomly assigned to consume daily either 25 g of a beef supplement (BEEF) or an isoenergetic carbohydrates (CHO) supplement for 8 weeks, with both conditions being separated by a 5-week washout period. Outcomes, including blood analyses and anthropometrical measurements, were assessed before and after each 8-week intervention.

RESULTS

No effects of supplement condition were observed on body mass nor on skinfold thicknesses, but BEEF induced significant and large benefits over CHO in the thigh cross-sectional area (3.02%, 95%CI = 1.33 to 4.71%; p = 0.028, d = 1.22). Contrary to CHO, BEEF presented a significant increase in vastus lateralis muscle thickness (p = 0.046), but differences between conditions were not significant (p = 0.173, d = 0.87). Although a significantly more favorable testosterone-to-cortisol ratio (TCR) was observed for BEEF over CHO (37%, 95% CI = 5 to 68%; p = 0.028, d = 1.29), no significant differences were found for the hematological variables (i.e., iron, ferritin, red blood cell count, hemoglobin or hematocrit).

CONCLUSION

Beef protein supplementation seems to facilitate a more favorable anabolic environment (i.e., increased TCR and muscle mass) in male elite triathletes, with no impact on hematological variables.

Protein supplementation increases adaptations to endurance training: A systematic review and meta-analysis

BACKGROUND

Trials that assessed the impact of protein supplementation on endurance training adaptations have reported conflicting findings.

OBJECTIVE

To determine the impact of protein supplementation during chronic endurance training on aerobic capacity, body composition and exercise performance in healthy and clinical populations.

DESIGN

A systematic database search was conducted for randomised controlled trials addressing the effects of protein supplementation during endurance training on aerobic capacity, body composition and exercise performance in PubMed, Embase, Web of Science, and CINAHL. Meta-analyses were performed to outline the overall effects of protein supplementation with all studies containing endurance training components. The effects of endurance training and add-on effects of protein supplementation were evaluated by the meta-analyses with endurance training-focused studies.

RESULTS

Nineteen studies and 1162 participants contributed to the analyses. Compared with the control group, the protein supplementation group demonstrated greater improvements in aerobic capacity measured by mixed peak oxygen uptake (V̇O_2peak) and peak workload power (W_peak) (standardised mean difference [SMD] = 0.36, 95% confidence interval [CI]: 0.05 to 0.67), and V̇O_2peak (mean difference [MD] = 0.89 mL‧kg^-1‧min^-1, 95% CI: 0.07 to 1.70); had a greater lean mass gain (MD = 0.32 kg, 95% CI: 0.07 to 0.58); and had a greater improvement in time trial performance (MD = -29.1s, 95% CI:-55.3 to -3.0). Secondary analyses showed that, in addition to the substantial improvement in V̇O_2peak (MD = 3.67 mL‧kg^-1‧min^-1, 95% CI: 2.32 to 5.03) attributed to endurance training, protein supplementation provided an additional 26.4% gain in V̇O_2peak (MD = 0.97 mL‧kg^-1‧min^-1, 95% CI: -0.03 to 1.97).

CONCLUSION

Protein supplementation further increased aerobic capacity, stimulated lean mass gain, and improved time trial performance during chronic endurance training in healthy and clinical populations. PROSPERO REGISTRATION NUMBER: (CRD42020155239).

Supplement with whey protein hydrolysate in contrast to carbohydrate supports mitochondrial adaptations in trained runners

Background

Protein supplementation has been suggested to augment endurance training adaptations by increasing mixed muscle and myofibrillar protein synthesis and lean body mass. However, a potential beneficial effect on mitochondrial adaptations is yet to be clarified.

The aim of the present study was to investigate the effect of consuming whey protein hydrolysate before and whey protein hydrolysate plus carbohydrate (PRO-CHO) after each exercise session during a six-week training period compared to similarly timed intake of isocaloric CHO supplements on biomarkers of mitochondrial biogenesis, VO_2max and performance in trained runners.

Methods

Twenty-four trained runners (VO_2max 60.7 ± 3.7 ml O₂ kg^− 1 min¹) completed a six-week block randomized controlled intervention period, consisting of progressive running training. Subjects were randomly assigned to either PRO-CHO or CHO and matched in pairs for gender, age, VO_2max, training and performance status. The PRO-CHO group ingested a protein beverage (0.3 g kg^− 1) before and protein-carbohydrate beverage (0.3 g protein kg^− 1 and 1 g carbohydrate kg^− 1) after each exercise session. The CHO group ingested an energy matched carbohydrate beverage. Resting muscle biopsies obtained pre and post intervention were analyzed for mitochondrial specific enzyme activity and mitochondrial protein content. Subjects completed a 6 K time trial (6 K TT) and a VO_2max test pre, midway (only 6 K TT) and post intervention.

Results

Following six weeks of endurance training Cytochrome C (Cyt C) protein content was significantly higher in the PRO-CHO group compared to the CHO group (p < 0.05), with several other mitochondrial proteins (Succinate dehydrogenase (SDHA), Cytochrome C oxidase (COX-IV), Voltage-dependent anion channel (VDAC), Heat shock protein 60 (HSP60), and Prohibitin (PHB1)) following a similar, but non-significant pattern (p = 0.07–0.14). β-hydroxyacyl-CoA dehydrogenase (HAD) activity was significantly lower after training in the CHO group (p < 0.01), but not in the PRO-CHO group (p = 0.24). VO_2max and 6 K TT was significantly improved after training with no significant difference between groups.

Conclusion

Intake of whey PRO hydrolysate before and whey PRO hydrolysate plus CHO after each exercise session during a six-week endurance training period may augment training effects on specific mitochondrial proteins compared to intake of iso-caloric CHO but does not alter VO_2max or 6 K TT performance.

Trial registration

clinicaltrials.gov, NCT03561337. Registered 6 June 2018 – Retrospectively registered.

Effect of carbohydrate-protein supplementation on endurance training adaptations

Purpose

To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training.

Methods

In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30–60 min at 70–75% maximal oxygen uptake (VO_2max) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM⁻¹) of carbohydrate (CHO) or an isocaloric carbohydrate–protein solution (CHO-P; 0.8 g carbohydrate kg BM⁻¹ + 0.8 g protein kg BM⁻¹) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up.

Results

Exercise training improved VO_2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min⁻¹ and 3.0 ± 2 mL kg⁻¹ min⁻¹, respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL⁻¹) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL⁻¹; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training.

Conclusion

Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO_2max was similar between groups.

Dose-response effects of dietary protein on muscle protein synthesis during recovery from endurance exercise in young men: a double-blind randomized trial

BACKGROUND

Protein ingestion increases skeletal muscle protein synthesis rates during recovery from endurance exercise.

OBJECTIVES

We aimed to determine the effect of graded doses of dietary protein co-ingested with carbohydrate on whole-body protein metabolism, and skeletal muscle myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates during recovery from endurance exercise.

METHODS

In a randomized, double-blind, parallel-group design, 48 healthy, young, endurance-trained men (mean ± SEM age: 27 ± 1 y) received a primed continuous infusion of l-[ring-2H5]-phenylalanine, l-[ring-3,5-2H2]-tyrosine, and l-[1-13C]-leucine and ingested 45 g carbohydrate with either 0 (0 g PRO), 15 (15 g PRO), 30 (30 g PRO), or 45 (45 g PRO) g intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled milk protein after endurance exercise. Blood and muscle biopsy samples were collected over 360 min of postexercise recovery to assess whole-body protein metabolism and both MyoPS and MitoPS rates.

RESULTS

Protein intake resulted in ∼70%-74% of the ingested protein-derived phenylalanine appearing in the circulation. Whole-body net protein balance increased dose-dependently after ingestion of 0, 15, 30, or 45 g protein (mean ± SEM: -0.31± 0.16, 5.08 ± 0.21, 10.04 ± 0.30, and 13.49 ± 0.55 μmol phenylalanine · kg-1 · h-1, respectively; P < 0.001). 30 g PRO stimulated a ∼46% increase in MyoPS rates (%/h) compared with 0 g PRO and was sufficient to maximize MyoPS rates after endurance exercise. MitoPS rates were not increased after protein ingestion; however, incorporation of dietary protein-derived l-[1-13C]-phenylalanine into de novo mitochondrial protein increased dose-dependently after ingestion of 15, 30, and 45 g protein at 360 min postexercise (0.018 ± 0.002, 0.034 ± 0.002, and 0.046 ± 0.003 mole percentage excess, respectively; P < 0.001).

CONCLUSIONS

Protein ingested after endurance exercise is efficiently digested and absorbed into the circulation. Whole-body net protein balance and dietary protein-derived amino acid incorporation into mitochondrial protein respond to increasing protein intake in a dose-dependent manner. Ingestion of 30 g protein is sufficient to maximize MyoPS rates during recovery from a single bout of endurance exercise.This trial was registered at trialregister.nl as NTR5111.

Habitual high-protein diet does not influence muscle protein synthesis in response to acute resistance exercise in rats

OBJECTIVES

Resistance training combined with consumption of a high-protein diet (HPD) is typically recommended to increase muscle mass, as both acute resistance exercise (RE) and dietary protein intake stimulate mechanistic target of rapamycin complex 1 (mTORC1) and muscle protein synthesis (MPS). However, the effect of chronic HPD consumption on MPS response to an acute RE remains to be determined.

METHODS

Male Sprague-Dawley rats aged 10 wk were fed HPD (50 kcal % protein, for 4 wk) or normal protein diet (NPD; 20 kcal % protein). After the 4-wk dietary intervention, the rats were fasted overnight and the right gastrocnemius muscle was subjected to percutaneous electrical stimulation to mimic acute RE, whereas the left gastrocnemius muscle served as control. The rats were sacrificed 6 h after exercise and the tissues were sampled immediately.

RESULTS

The HPD group showed significantly lower fat mass and higher skeletal muscle mass than the NPD group without affecting body weight. Resting mTORC1 activity did not differ between the groups. Additionally, resting MPS was also unchanged after HPD. Acute RE significantly increased mTORC1 activity and MPS in both groups. However, differences in diet did not influence the response of mTORC1 activation to acute RE. Furthermore, HPD did not affect the response of MPS to acute RE.

CONCLUSION

The present results suggested that although 4 wk of HPD reduces body fat and increases skeletal muscle mass, it does not affect muscle protein synthesis at basal state, and in response to acute RE.

Effects of protein supplementation on aerobic training-induced gains in cardiopulmonary fitness, muscle mass, and functional performance in chronic stroke: A randomized controlled pilot study

BACKGROUND & AIMS

The beneficial effects of protein supplementation on aerobic exercise-induced gains in patients with stroke are currently unknown. This study evaluated the feasibility and potential value of protein supplementation with aerobic exercise among stroke survivors.

METHODS

This double-blinded randomized controlled pilot study included 20 ambulatory persons with chronic (>6 months) stroke randomly assigned to either the protein (PRO) or carbohydrate (CHO) group. All participants received three 40-min cycling ergometric training sessions a week for 8 weeks. Training intensity at 60%-80% heart rate reserve was determined using cardiopulmonary exercise pretests. Immediately before and after each session, the PRO group received a 20-g protein-rich supplement, and the CHO group received a 20-g calorie-matched carbohydrate-rich supplement. Outcomes included changes in body composition, cardiopulmonary capacity, and clinical functional performance.

RESULTS

Those completing the protocol (n = 18) received 18-24 cycling training sessions, achieving target training intensity without major adverse effects. Of the two groups, the PRO group tended to obtain greater aerobic capacity (effect size [ES]>0.5 in every cardiopulmonary index), greater improvements in functional performance (0.25 < ES < 1.00 in various clinical tests), and greater total lean mass versus total fat mass (ES = 0.52).

CONCLUSIONS

Protein supplementation with aerobic exercise training tends to improve body composition, cardiopulmonary fitness, and function among persons with stroke. This study protocol is feasible, and future trials with larger sample sizes could confirm these results.

TRIAL REGISTRATION

NCT03244527.

Effect of Oral Nutritional Supplementation With and Without Exercise on Nutritional Status and Physical Function of Adult Hemodialysis Patients: A Parallel Controlled Clinical Trial (AVANTE-HEMO Study)

OBJECTIVE

Protein energy wasting affects the nutritional status (NS) and physical function (PF) of dialysis patients. Among the different anabolic strategies to improve NS and PF, oral nutritional supplementation (ONS) and resistance exercise (RE) or aerobic exercise (AE) have been shown to be effective. Nevertheless, the combination of both anabolic strategies has not been completely evaluated. The aim of this study is to assess the effect of exercise combined with ONS versus ONS without exercise during hemodialysis sessions on PF and NS indicators.

METHODS

Young hemodialysis patients (29 ± 9.3 years) with predominantly unknown causes of renal disease (80%) were divided into the following 3 groups during a period of 12 weeks: (1) ONS (n = 15), (2) ONS + RE (n = 15), and (3) ONS + AE (n = 15). Anthropometric, biochemical, PF, and quality of life measurements were recorded at baseline and after 3 months. Repeated measures analysis of variance and effect sizes (Cohen's d) were used to assess the effect of exercise and nutrition (ISRCTN registry 10251828).

RESULTS

At the completion of the study, the ONS and ONS + RE groups exhibited statistically significant increases in body weight, body mass index, and in the percentage of fat mass (P < .05); the greatest effect sizes were observed in the ONS + RE group (d = 0.30 for body weight, d = 0.63 for body mass index, and d = 0.90 for the percentage of fat mass). Groups with RE and AE had statistically significant increases and large effect sizes in the six-minute walk test (RE: d = 0.94, P = .02; AE: d = 1.11, P = .03), sit-to-stand test (RE: d = 0.81, P = .041; AE: d = 1.20, P = .002), timed up and go test (RE: d = 1.04, P = .036; AE: d = 1.6, P = .000), and muscle strength (RE: d = 1.01, P = .000; AE: d = 0.60, P = .003). Regarding quality of life, the ONS + RE group had more areas of improvement at the end of the study, followed by the ONS + AE group. No statistically significant differences were found in the repeated measures ANOVA.

CONCLUSIONS

The combination of exercise with ONS had larger effects on PF than on ONS alone. Further studies to examine the impact of exercise on the effect of oral nutritional supplementation in dialysis patients are indicated.

Maximizing Post-exercise Anabolism: The Case for Relative Protein Intakes

Maximizing the post-exercise increase in muscle protein synthesis, especially of the contractile myofibrillar protein fraction, is essential to facilitate effective muscle remodeling, and enhance hypertrophic gains with resistance training. MPS is the primary regulated variable influencing muscle net balance with dietary amino acid ingestion representing the single most important nutritional variable enhancing post-exercise rates of muscle protein synthesis. Dose-response studies in average (i.e., ~80 kg) males have reported an absolute 20 g dose of high quality, rapidly digested protein maximizes mixed, and myofibrillar protein synthetic rates. However, it is unclear if these absolute protein intakes can be viewed in a “one size fits all” solution. Re-analysis of published literature in young adults suggests a relative single meal intake of ~0.31 g/kg of rapidly digested, high quality protein (i.e., whey) should be considered as a nutritional guideline for individuals of average body composition aiming to maximize post-exercise myofibrillar protein synthesis while minimizing irreversible amino acid oxidative catabolism that occurs with excessive intakes of this macronutrient. This muscle-specific bolus intake is lower than that reported to maximize whole body anabolism (i.e., ≥0.5 g/kg). Review of the available literature suggests that potential confounders such as the co-ingestion of carbohydrate, sex, and amount of active muscle mass do not represent significant barriers to the translation of this objectively determined relative protein intake. Additional research is warranted to elucidate the effective dose for proteins with suboptimal amino acid compositions (e.g., plant-based), and/or slower digestion rates as well as whether recommendations are appreciably affected by other physiological conditions such endurance exercise, high habitual daily protein ingestion, aging, obesity, and/or periods of chronic negative energy balance.

Protein-Based Supplementation to Enhance Recovery in Team Sports: What is the Evidence?

Protein supplementation is a major nutritional practice among professional and amateur team-sport athletes representing a market of $5 billion in the USA alone. This practice, however, may not be supported by evidence-based science. Our objective as to present a thorough review of literature investigating the effects of protein supplementation on performance recovery and exercise-induced muscle damage following team-sport activity. PubMed-derived, full English language articles investigating the effects of protein-based supplementation/feeding on skeletal muscle performance, muscle damage and inflammatory status during recovery following team-sport activity were included. Studies investigated professional or amateur team-sport athletes participating in regular training and competition as well as examining the impact of protein supplementation on performance, muscle damage/soreness and inflammatory markers after team-sport activity. Finally, ten articles (150 participants) met the inclusion criteria. Experimental designs were evaluated for confounders. All protocols employing team-sport activity increased systemic muscle damage indicators and inflammatory markers and deteriorated performance during recovery. Protein-based supplementation attenuated the rise in muscle damage markers and enhanced performance recovery in six (60% of the studies included) and three (30% of the studies included) out of 10 studies, respectively. In contrast, immunity and muscle soreness remained unaffected by protein ingestion, independent of dosage and distribution pattern. In conclusion, there are limited and inconsistent data showing that protein supplementation may enhance performance recovery following team-sport activity despite an attenuation of indirect markers of muscle damage. Interpretation of results is limited by small sample sizes, high variability in tested supplements, participants' training level, length of recovery periods, absence of direct measurement of myofibrillar disruption, protein turnover and protein metabolism, and lack of dietary monitoring during experimentation.

Molecular regulation of human skeletal muscle protein synthesis in response to exercise and nutrients: a compass for overcoming age-related anabolic resistance

Skeletal muscle mass, a strong predictor of longevity and health in humans, is determined by the balance of two cellular processes, muscle protein synthesis (MPS) and muscle protein breakdown. MPS seems to be particularly sensitive to changes in mechanical load and/or nutritional status; therefore, much research has focused on understanding the molecular mechanisms that underpin this cellular process. Furthermore, older individuals display an attenuated MPS response to anabolic stimuli, termed anabolic resistance, which has a negative impact on muscle mass and function, as well as quality of life. Therefore, an understanding of which, if any, molecular mechanisms contribute to anabolic resistance of MPS is of vital importance in formulation of therapeutic interventions for such populations. This review summarizes the current knowledge of the mechanisms that underpin MPS, which are broadly divided into mechanistic target of rapamycin complex 1 (mTORC1)-dependent, mTORC1-independent, and ribosomal biogenesis-related, and describes the evidence that shows how they are regulated by anabolic stimuli (exercise and/or nutrition) in healthy human skeletal muscle. This review also summarizes evidence regarding which of these mechanisms may be implicated in age-related skeletal muscle anabolic resistance and provides recommendations for future avenues of research that can expand our knowledge of this area.

Protein supplementation elicits greater gains in maximal oxygen uptake capacity and stimulates lean mass accretion during prolonged endurance training: a double-blind randomized controlled trial

BACKGROUND

Endurance training induces numerous cardiovascular and skeletal muscle adaptations, thereby increasing maximal oxygen uptake capacity (VO2max). Whether protein supplementation enhances these adaptations remains unclear.

OBJECTIVE

The present study was designed to determine the impact of protein supplementation on changes in VO2max during prolonged endurance training.

METHODS

We used a double-blind randomized controlled trial with repeated measures among 44 recreationally active, young males. Subjects performed 3 endurance training sessions per week for 10 wk. Supplements were provided immediately after each exercise session and daily before sleep, providing either protein (PRO group; n = 19; 21.5 ± 0.4 y) or an isocaloric amount of carbohydrate as control (CON group; n = 21; 22.5 ± 0.5 y). The VO2max, simulated 10-km time trial performance, and body composition (dual-energy X-ray absorptiometry) were measured before and after 5 and 10 wk of endurance training. Fasting skeletal muscle tissue samples were taken before and after 5 and 10 wk to measure skeletal muscle oxidative capacity, and fasting blood samples were taken every 2 wk to measure hematological factors.

RESULTS

VO2max increased to a greater extent in the PRO group than in the CON group after 5 wk (from 49.9 ± 0.8 to 54.9 ± 1.1 vs 50.8 ± 0.9 to 53.0 ± 1.1 mL · kg-1 · min-1; P < 0.05) and 10 wk (from 49.9 ± 0.8 to 55.4 ± 0.9 vs 50.8 ± 0.9 to 53.9 ± 1.2 mL · kg-1 · min-1; P < 0.05). Lean body mass increased in the PRO group whereas lean body mass in the CON group remained stable during the first 5 wk (1.5 ± 0.2 vs 0.1 ± 0.3 kg; P < 0.05) and after 10 wk (1.5 ± 0.3 vs 0.4 ± 0.3 kg; P < 0.05). Throughout the intervention, fat mass reduced significantly in the PRO group and there were no changes in the CON group after 5 wk (-0.6 ± 0.2 vs -0.1 ± 0.2 kg; P > 0.05) and 10 wk (-1.2 ± 0.4 vs -0.2 ± 0.2 kg; P < 0.05).

CONCLUSIONS

Protein supplementation elicited greater gains in VO2max and stimulated lean mass accretion but did not improve skeletal muscle oxidative capacity and endurance performance during 10 wk of endurance training in healthy, young males. This trial was registered at clinicaltrials.gov as NCT03462381.

Presleep Protein Supplementation Does Not Improve Recovery During Consecutive Days of Intense Endurance Training: A Randomized Controlled Trial

Recent studies demonstrate that protein ingestion immediately before sleep improves muscle recovery during the night following resistance exercise. Whether this feeding strategy benefits recovery from endurance training has yet to be established. The aim of this study was to investigate the effects of whey protein isolate ingested every night before sleep on subsequent performance and circulatory markers of muscular recovery during a week of intensified endurance training mimicking a training camp. In a parallel design, 32 trained runners underwent a 1-week intervention with a rigorously controlled diet (carbohydrate = 7.2 g·kg^-1·day^-1, protein = 1.8 g·kg^-1·day^-1, and fat = 1.0 g·kg^-1·day^-1) and exercise program (11 sessions) while receiving either a protein (0.5 g·kg^-1·day^-1) or carbohydrate (0.5 g·kg^-1·day^-1) beverage every night before sleep. Blood samples were obtained on the morning of Days 1, 4, 7, and 8 and analyzed for markers of muscle damage (creatine kinase, lactate dehydrogenase, and myoglobin). The postintervention 5-km time-trial performance was significantly impaired in both groups (11 ± 24 s, p < .01). Plasma creatine kinase (227% ± 221%, p < .01), lactate dehydrogenase (18% ± 22%, p < .01), and myoglobin (72% ± 62%, p < .01) increased gradually throughout the week with no difference between the groups (p > .05). In conclusion, the presleep protein ingestion did not reduce the decline in performance or ameliorate the rise of circulatory markers of muscle damage during a week of intensified training when compared with the isocaloric carbohydrate ingestion.

Ketone ester supplementation blunts overreaching symptoms during endurance training overload

KEY POINTS

Overload training is required for sustained performance gain in athletes (functional overreaching). However, excess overload may result in a catabolic state which causes performance decrements for weeks (non-functional overreaching) up to months (overtraining). Blood ketone bodies can attenuate training- or fasting-induced catabolic events. Therefore, we investigated whether increasing blood ketone levels by oral ketone ester (KE) intake can protect against endurance training-induced overreaching. We show for the first time that KE intake following exercise markedly blunts the development of physiological symptoms indicating overreaching, and at the same time significantly enhances endurance exercise performance. We provide preliminary data to indicate that growth differentiation factor 15 (GDF15) may be a relevant hormonal marker to diagnose the development of overtraining. Collectively, our data indicate that ketone ester intake is a potent nutritional strategy to prevent the development of non-functional overreaching and to stimulate endurance exercise performance.

ABSTRACT

It is well known that elevated blood ketones attenuate net muscle protein breakdown, as well as negate catabolic events, during energy deficit. Therefore, we hypothesized that oral ketones can blunt endurance training-induced overreaching. Fit male subjects participated in two daily training sessions (3 weeks, 6 days/week) while receiving either a ketone ester (KE, n = 9) or a control drink (CON, n = 9) following each session. Sustainable training load in week 3 as well as power output in the final 30 min of a 2-h standardized endurance session were 15% higher in KE than in CON (both P < 0.05). KE inhibited the training-induced increase in nocturnal adrenaline (P < 0.01) and noradrenaline (P < 0.01) excretion, as well as blunted the decrease in resting (CON: -6 ± 2 bpm; KE: +2 ± 3 bpm, P < 0.05), submaximal (CON: -15 ± 3 bpm; KE: -7 ± 2 bpm, P < 0.05) and maximal (CON: -17 ± 2 bpm; KE: -10 ± 2 bpm, P < 0.01) heart rate. Energy balance during the training period spontaneously turned negative in CON (-2135 kJ/day), but not in KE (+198 kJ/day). The training consistently increased growth differentiation factor 15 (GDF15), but ∼2-fold more in CON than in KE (P < 0.05). In addition, delta GDF15 correlated with the training-induced drop in maximal heart rate (r = 0.60, P < 0.001) and decrease in osteocalcin (r = 0.61, P < 0.01). Other measurements such as blood ACTH, cortisol, IL-6, leptin, ghrelin and lymphocyte count, and muscle glycogen content did not differentiate KE from CON. In conclusion, KE during strenuous endurance training attenuates the development of overreaching. We also identify GDF15 as a possible marker of overtraining.

Dietary Fuels in Athletic Performance

Focusing on daily nutrition is important for athletes to perform and adapt optimally to exercise training. The major roles of an athlete's daily diet are to supply the substrates needed to cover the energy demands for exercise, to ensure quick recovery between exercise bouts, to optimize adaptations to exercise training, and to stay healthy. The major energy substrates for exercising skeletal muscles are carbohydrate and fat stores. Optimizing the timing and type of energy intake and the amount of dietary macronutrients is essential to ensure peak training and competition performance, and these strategies play important roles in modulating skeletal muscle adaptations to endurance and resistance training. In this review, recent advances in nutritional strategies designed to optimize exercise-induced adaptations in skeletal muscle are discussed, with an emphasis on mechanistic approaches, by describing the physiological mechanisms that provide the basis for different nutrition regimens.

Indicator amino acid oxidation protein requirement estimate in endurance-trained men 24 h postexercise exceeds both the EAR and current athlete guidelines

Despite studies indicating increased protein requirements in strength-trained or endurance-trained (ET) individuals, the Institute of Medicine has concluded that "no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise," and the controversy regarding exercise effects on protein requirements continues. The objective of this study was to determine the dietary protein requirement of healthy young ET men (≥1 yr training experience) 24 h post exercise (to minimize any acute effects of the previous training session) by measuring the oxidation of ingested l-[1-¹³C]phenylalanine to ¹³CO₂ in response to graded intakes of protein (indicator amino acid oxidation technique). Eight men [maximal oxygen consumption 64.1 ml·kg^-1·min^-1 (SD 3.7)] were each studied 24 h postexercise repeatedly with protein intakes ranging from 0.3 to 3.5 g·kg^-1·day^-1. Protein was fed as an amino acid mixture based on the protein pattern in egg, except for phenylalanine and tyrosine, which were maintained at constant amounts across all protein intakes. For 2 days before the study day, all participants consumed 1.6 g protein·kg^-1·day^-1. The estimated average requirement (EAR) for protein was determined by applying a nonlinear mixed-effects change-point regression analysis to F¹³CO₂ (label tracer oxidation in ¹³CO₂ breath), which identified a breakpoint in the F¹³CO₂ in response to the graded amounts of protein. The EAR for protein and the upper 95% confidence interval were 2.1 and 2.6 g·kg^-1·day^-1, respectively. These data suggest that the protein EAR for ET men 24 h postexercise exceeds the Institute of Medicine EAR and established athlete guidelines by ~3.5- and 1.3-fold, respectively.

Efficacy and Safety of Whey Protein Supplements on Vital Sign and Physical Performance Among Athletes: A Network Meta-Analysis

Introduction: Athletes train physically to reach beyond their potential maximum aerobic threshold. Whey protein supplements (WPS) are often used in conjunction with physiotherapy and psychotherapy to regain better vital sign and physical performances. This review aimed to explore the clinical evidence on the efficacy and safety of WPS in sports performance and recovery among athletes.

Methodology: A comprehensive literature search was performed to identify relevant randomized control trials (RCTs) that investigated the efficacy and safety of WPS on the vital sign and physical performance among athletes. The Cochrane Risk of Bias (ROB) Assessment tools were used to assess the quality of the studies. Meta-analysis was conducted using the frequentist model with STATA version 14.2®.

Results: A total of 333,257 research articles were identified out of which 20 RCTs were included for qualitative synthesis and network meta-analysis with 351 participants. Among the studies, 7 had low ROB and 3 RCTs had high ROB. Of these 20 trials, 16 trials were randomized clinical trials which compared whey protein supplements (WPS) with various comparators i.e., L-alanine, bovine colostrum, carbohydrate, casein, leucine, maltodextrin, rice, protein + caffeine were compared with placebo. Analysis from the pairwise meta-analysis revealed that for respiratory exchange ratio (RER) WPS was found to be significantly improving compared to maltodextrin (WMD = 0.012; 95%CI = 0.001, 0.023). Similarity to RPE (Rate Perceived Exertion), slight difference between WPS and the comparators, however, when the estimation was favorable to the comparators, there was moderate-high heterogeneity. For VO_2max, high heterogeneity appeared when WPS compared to maltodextrin with the I² = 97.8% (WMD = 4.064; 95% CI = −4.230, 12.359), meanwhile bovine colostrum (WMD = −2.658; 95%CI = −6.180, 0.865) only comparator that was better than WPS. According to the estimated effect of the supplements on physical performance outcome results, maximum power (8 studies, 185 athletes), highest ranked was bovine colostrum (SUCRA = 70.7%) and the lowest ranked was placebo (SUCRA = 17.9%), yet all insignificant. Then again, on average power (nine studies, 187 athletes), WPS was the highest ranked (SUCRA = 75.4 %) about −112.00 watt (−187.91, −36.08) and most of the estimations were significant. Body mass was reported in 10 studies (171 athletes), carbohydrate may be at the highest ranked (SUCRA = 66.9%) but it is insignificant. Thought the second highest ranked was WPS (SUCRA = 64.7%) and it is significant (WMD = −6.89 kg; CI = −8.24, −5.54).

Conclusion: The findings of this review support the efficacy and safety of WPS as an ergogenic aid on athletes' sports performance and recovery. The overall quality of clinical evidence was found to be valid and reliable from the comprehensive search strategy and ROB assessment.

Whey Protein Isolate Supplementation While Endurance Training Does Not Alter Cycling Performance or Immune Responses at Rest or After Exercise

This study examined whey protein isolate supplementation combined with endurance training on cycling performance, aerobic fitness and immune cell responses. Eighteen male cyclists were randomly assigned to either placebo (PLA) or whey protein supplementation (WS; 1.0 g·kg body mass⁻¹·d⁻¹ in addition to their dietary intake). Both groups completed the identical endurance training program, 4 days per week for 6 weeks. Blood samples were obtained at rest and after 5 and 60 min of recovery from a simulated 40 km cycling time trial (TT) and were repeated after training. Baseline dietary intake of protein prior to supplementation was 1.52 ± 0.45 and 1.46 ± 0.44 g·kg body mass⁻¹·d⁻¹ for the WS and PLA groups, respectively. There were similar improvements in TT performance (WS: 71.47 ± 12.17 to 64.38 ± 8.09 min; PLA: 72.33 ± 12.79 to 61.13 ± 8.97 min), and peak oxygen uptake (WS: 52.3 ± 6.1 to 56.1 ± 5.4 mL·kg⁻¹·min⁻¹; PLA: 50.0 ± 7.1 to 54.9 ± 5.1 mL·kg⁻¹·min⁻¹) after training in both groups. White blood cells (WBC) and neutrophil counts were elevated 5 min after the TT and further increased after 60 min (P < 0.05). The exercise-induced increase in WBC and neutrophil counts at 5 and 60 min after the TT were attenuated after training compared to before training (P < 0.05). Lymphocytes increased 5 min after the TT and decreased below rest after 60 min of recovery (P < 0.05). Following training lymphocytes were lower after 60 min of recovery compared to before training. There was no change in natural killer cell activity with exercise, training or between groups. It was concluded that whey protein isolate supplementation while endurance training did not differentially change cycling performance or the immune response at rest or after exercise. However, endurance training did alter performance, aerobic fitness and some post exercise immune cell counts.

Translocation and protein complex co-localization of mTOR is associated with postprandial myofibrillar protein synthesis at rest and after endurance exercise

Translocation and colocalization of mechanistic target of rapamycin complex 1 (mTORC1) with regulatory proteins represents a critical step in translation initiation of protein synthesis in vitro. However, mechanistic insight into the control of postprandial skeletal muscle protein synthesis rates at rest and after an acute bout of endurance exercise in humans is lacking. In crossover trials, eight endurance‐trained men received primed‐continuous infusions of L‐[ring‐²H₅]phenylalanine and consumed a mixed‐macronutrient meal (18 g protein, 60 g carbohydrates, 17 g fat) at rest (REST) and after 60 min of treadmill running at 70% VO_2peak (EX). Skeletal muscle biopsies were collected to measure changes in phosphorylation and colocalization in the mTORC1‐pathway, in addition to rates of myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis. MyoPS increased (P < 0.05) above fasted in REST (~2.1‐fold) and EX (~twofold) during the 300 min postprandial period, with no corresponding changes in MitoPS (P > 0.05). TSC2/Rheb colocalization decreased below fasted at 60 and 300 min after feeding in REST and EX (P < 0.01). mTOR colocalization with Rheb increased above fasted at 60 and 300 min after feeding in REST and EX (P < 0.01), which was consistent with an increased phosphorylation 4E‐BP1^Thr37/46 and rpS6^ser240/244 at 60 min. Our data suggest that MyoPS, but not MitoPS, is primarily nutrient responsive in trained young men at rest and after endurance exercise. The postprandial increase in MyoPS is associated with an increase in mTOR/Rheb colocalization and a reciprocal decrease in TSC2/Rheb colocalization and thus likely represent important regulatory events for in vivo skeletal muscle myofibrillar mRNA translation in humans.

Myofibrillar and Mitochondrial Protein Synthesis Rates Do Not Differ in Young Men Following the Ingestion of Carbohydrate with Whey, Soy, or Leucine-Enriched Soy Protein after Concurrent Resistance- and Endurance-Type Exercise

BACKGROUND

Protein ingestion during recovery from resistance-type exercise increases postexercise muscle protein synthesis rates. Whey protein has been reported to have greater anabolic properties than soy protein, an effect which may be attributed to the higher leucine content of whey.

OBJECTIVE

The objective of this study was to compare postprandial myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates after ingestion of carbohydrate with whey, soy, or soy protein enriched with free leucine (to match the leucine content of whey) during recovery from a single bout of concurrent resistance- and endurance-type exercise in young healthy men.

METHODS

In a randomized, double-blind, parallel-group design, 36 healthy young recreationally active men (mean ± SEM age: 23 ± 0.4 y) received a primed continuous infusion of l-[ring-13C6]-phenylalanine and l-[ring-3,5-2H2]-tyrosine and ingested 45 g carbohydrate with 20 g protein from whey (WHEY), soy (SOY), or leucine-enriched soy (SOY + LEU) after concurrent resistance- and endurance-type exercise. Blood and muscle biopsies were collected over a 360 min postexercise recovery period to assess MyoPS and MitoPS rates, and associated signaling through the mammalian target of rapamycin complex 1 (mTORC1).

RESULTS

Postprandial peak plasma leucine concentrations were significantly higher in WHEY (mean ± SEM: 322 ± 10 μmol/L) and SOY + LEU (328 ± 14 μmol/L) compared with SOY (216 ± 6 μmol/L) (P < 0.05). Despite the apparent differences in plasma leucinemia, MyoPS (WHEY: 0.054 ± 0.002; SOY: 0.053 ± 0.004; SOY + LEU: 0.056 ± 0.004%·h-1; P = 0.83), and MitoPS (WHEY: 0.061 ± 0.004; SOY: 0.061 ± 0.006; SOY + LEU: 0.063 ± 0.004%·h-1; P = 0.96) rates over the entire 360 min recovery period did not differ between treatments. Similarly, signaling through mTORC1Ser2448, p70S6kThr389, 4E-BP1Thr37/46, and rpS6Ser235/236 was similar between treatments.

CONCLUSION

Postexercise MyoPS and MitoPS rates do not differ after co-ingestion of carbohydrate with 20 g protein from whey, soy, or leucine-enriched soy protein during 360 min of recovery from concurrent resistance- and endurance-type exercise in young, recreationally active men. This trial was registered at Nederlands Trial Register as NTR5098.

Myofibrillar and Mitochondrial Protein Synthesis Rates Do Not Differ in Young Men Following the Ingestion of Carbohydrate with Milk Protein, Whey, or Micellar Casein after Concurrent Resistance- and Endurance-Type Exercise

BACKGROUND

Whey and micellar casein are high-quality dairy proteins that can stimulate postprandial muscle protein synthesis rates. How whey and casein compare with milk protein in their capacity to stimulate postprandial myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis rates during postexercise recovery is currently unknown.

OBJECTIVE

The objective of this study was to compare postprandial MyoPS and MitoPS rates after protein-carbohydrate co-ingestion with milk protein, whey, or micellar casein during recovery from a single bout of concurrent resistance- and endurance-type exercise in young healthy men.

METHODS

In a randomized, double-blind, parallel-group design, 48 healthy, young, recreationally active men (mean ± SEM age: 23 ± 0.3 y) received a primed continuous infusion of L-[ring-13C6]-phenylalanine and L-[ring-3,5-2H2]-tyrosine and ingested 45 g carbohydrate with 0 g protein (CHO), 20 g milk protein (MILK), 20 g whey protein (WHEY), or 20 g micellar casein protein (CASEIN) after a sequential bout of resistance- and endurance-type exercise (i.e., concurrent exercise). Blood and muscle biopsies were collected over 360 min during recovery from exercise to assess MyoPS and MitoPS rates and signaling through mammalian target of rapamycin complex 1 (mTORC1).

RESULTS

Despite temporal differences in postprandial plasma leucine concentrations between treatments (P < 0.001), MyoPS rates over 360 min of recovery did not differ between treatments (CHO: 0.049% ± 0.003%/h; MILK: 0.059% ± 0.003%/h; WHEY: 0.054% ± 0.002%/h; CASEIN: 0.059% ± 0.005%/h; P = 0.11). When MILK, WHEY, and CASEIN were pooled into a single group (PROTEIN), protein co-ingestion resulted in greater MyoPS rates compared with CHO (PROTEIN: 0.057% ± 0.002%/h; CHO: 0.049% ± 0.003%/h; P = 0.04). MitoPS rates and signaling through the mTORC1 pathway were similar between treatments.

CONCLUSION

MyoPS and MitoPS rates do not differ after co-ingestion of either milk protein, whey protein, or micellar casein protein with carbohydrate during recovery from a single bout of concurrent resistance- and endurance-type exercise in recreationally active young men. Co-ingestion of protein with carbohydrate results in greater MyoPS, but not MitoPS rates, when compared with the ingestion of carbohydrate only during recovery from concurrent exercise. This trial was registered at Nederlands Trial Register: NTR5098.

Optimizing recovery to support multi-evening cycling competition performance

Road criterium and track bicycle racing occur at high speeds, demand repeated high power outputs, last 10-90 min, and offer little chance for recovery after the event. Consecutive evenings of criterium and track racing are respectively known as speed-week or six-day events and take place in evening hours over the course of a week. Given the schedule and timing of these competitions, return to homeostasis can be compromised. No recommendations exist on how to optimize recovery for cyclists participating in these types of repeated evening competitions. Criterium and track cyclists spend considerable time, near and above the individual lactate threshold and therefore mostly utilize carbohydrate as their chief energy substrate. Henceforth, pre - and post-race nutrition and hydration is examined and recommendations are brought forward for carbohydrate, protein, and fluid intake. As evening high-intensity exercise perturbs sleep, strategies to optimize sleep are discussed and recommendations for an optimal sleep environment are given. Active recovery is examined, and the benefits of a short duration low intensity exercise reviewed. Passive recovery methods such as compression garments and cold water immersion are recommended, while evidence for massage, pneumatic compression devices, and neuromuscular electrical stimulation is still lacking. Optimizing recovery strategies will facilitate a return to the resting state following strenuous night competition.

Protein intake in the early recovery period after exhaustive exercise improves performance the following day

The aim of the present study was to investigate the effect of protein and carbohydrate ingestion during early recovery from exhaustive exercise on performance after 18-h recovery. Eight elite cyclists (V̇o2max: 74.0 ± 1.6 ml·kg−1·min−1) completed two exercise and diet interventions in a double-blinded, randomized, crossover design. Participants cycled first at 73% of V̇o2max (W73%) followed by 1-min intervals at 90% of V̇o2max until exhaustion. During the first 2 h of recovery, participants ingested either 1.2 g carbohydrate·kg−1·h−1 (CHO) or 0.8 g carbohydrate + 0.4 g protein·kg−1·h−1 (CHO + PROT). The diet during the remaining recovery period was similar for both interventions and adjusted to body weight. After an 18-h recovery, cycling performance was assessed with a 10-s sprint test, 30 min of cycling at W73%, and a cycling time trial (TT). The TT was 8.5% faster (41:53 ± 1:51 vs. 45:26 ± 1:32 min; P < 0.03) after CHO + PROT compared with CHO. Mean power output during the sprints was 3.7% higher in CHO + PROT compared with CHO (1,063 ± 54 vs. 1,026 ± 53 W; P = 0.01). Nitrogen balance in the recovery period was negative in CHO and neutral in CHO + PROT (−82.4 ± 11.5 vs. 7.0 ± 15.4 mg/kg; P < 0.01). In conclusion, TT and sprint performances were improved 18 h after exhaustive cycling by CHO + PROT supplementation during the first 2 h of recovery compared with isoenergetic CHO supplementation. Our results indicate that intake of carbohydrate plus protein after exhaustive endurance exercise more rapidly converts the body from a catabolic to an anabolic state than carbohydrate alone, thus speeding recovery and improving subsequent cycling performance.

NEW & NOTEWORTHY Prolonged high intensity endurance exercise depends on glycogen utilization and high oxidative capacity. Still, exhaustion develops and effective recovery strategies are required to compete in multiday stage races. We show that coingestion of protein and carbohydrate during the first 2 h of recovery is superior to isoenergetic intake of carbohydrate to stimulate recovery, and improves both endurance time-trial and 10-s sprint performance the following day in elite cyclists.

Protein Supplementation Throughout 10 Weeks of Progressive Run Training Is Not Beneficial for Time Trial Improvement

Introduction: Protein supplementation is proposed to promote recovery and adaptation following endurance exercise. While prior literature demonstrates improved performance when supplementing protein during or following endurance exercise, chronic supplementation research is limited.

Methods: Runners (VO₂peak = 53.6 ± 8.9 ml/kg/min) were counter-balanced into a placebo group (PLA; n = 8) or protein group (PRO; n = 9) based on sex and VO₂peak, and underwent 10 weeks of progressive endurance training. Prior to training, body composition, blood cell differentials, non-invasive mitochondrial capacity using near-infrared spectroscopy, and a 5 km treadmill time trial (TT) were evaluated. Progressive training then commenced (5–10% increase in weekly volume with a recovery week following 3 weeks of training) whereby PRO supplemented with 25 g of whey protein following workouts and prior to sleep (additional 50 g daily). PLA supplemented similarly with a < 1 g sugar pill per day. Following training, participants were reanalyzed for the aforementioned tests.

Results: VO₂peak and initial 5 km TT were not significantly different between groups. PRO consumed significantly more dietary protein throughout the training period (PRO = 132 g/d or 2.1 g/kg/day; PLA = 84 g/d or 1.2 g/kg/day). Running volume increased significantly over time, but was not significantly different between groups throughout training. Blood measures were unaltered with training or supplementation. Mitochondrial capacity trended toward improving over time (time p = 0.063) with no difference between groups. PLA increased lean mass 0.7 kg (p < 0.05) while PRO experienced infinitesimal change (−0.1 kg, interaction p = 0.049). PLA improved 5 km TT performance 6.4% (1 min 31 s), while PRO improved only 2.7% (40 s) (interaction p = 0.080).

Conclusion: This is the first evidence to suggest long-term protein supplementation during progressive run training is not beneficial for runners.

Role of Functional Beverages on Sport Performance and Recovery

Functional beverages represent a palatable and efficient way to hydrate and reintegrate electrolytes, carbohydrates, and other nutrients employed and/or lost during physical training and/or competitions. Bodily hydration during sporting activity is one of the best indicators of health in athletes and can be a limiting factor for sport performance. Indeed, dehydration strongly decreases athletic performance until it is a risk to health. As for other nutrients, each of them is reported to support athletes' needs both during the physical activity and/or in the post-workout. In this study, we review the current knowledge of macronutrient-enriched functional beverages in sport taking into account the athletes' health, sports performance, and recovery.

Effects of Protein Supplementation on Performance and Recovery in Resistance and Endurance Training

There is robust evidence which shows that consuming protein pre- and/or post-workout induces a significant rise in muscle protein synthesis. It should be noted, however, that total daily caloric and protein intake over the long term play the most crucial dietary roles in facilitating adaptations to exercise. However, once these factors are accounted for, it appears that peri-exercise protein intake, particularly in the post-training period, plays a potentially useful role in terms of optimizing physical performance and positively influencing the subsequent recovery processes for both resistance training and endurance exercise. Factors that affect the utility of pre- or post-workout feeding include but are not necessarily limited to: training status (e.g., novice vs. advanced, or recreational vs. competitive athlete), duration of exercise, the number of training sessions per day, the number of competitive events per day, etc. From a purely pragmatic standpoint, consuming protein post-workout represents an opportunity to feed; this in turn contributes to one's total daily energy and protein intake. Furthermore, despite recent suggestions that one does not “need” to consume protein during the immediate (1 h or less) post-training time frame, it should be emphasized that consuming nothing offers no advantage and perhaps even a disadvantage. Thus, based on performance and recovery effects, it appears that the prudent approach would be to have athletes consume protein post-training and post-competition.

Dietary Manipulations Concurrent to Endurance Training

The role of an athlete's dietary intake (both timing and food type) goes beyond simply providing fuel to support the body's vital processes. Nutritional choices also have an impact on the metabolic adaptations to training. Over the past 20 years, research has suggested that strategically reducing carbohydrate (CHO) availability during an athlete's training can modify the metabolic responses in lieu of simply maintaining a high CHO diet. Several methods have been explored to manipulate CHO availability and include: Low-carb, high-fat (LCHF) diets, performing two-a-day training without glycogen restoration between sessions, and a "sleep-low" approach entailing a glycogen-depleting session in the evening without consuming CHO until after a morning training session performed in an overnight fasted state. Each of these methods can confer beneficial metabolic adaptations for the endurance athlete including increases in mitochondrial enzyme activity, mitochondrial content, and rates of fat oxidation, yet data showing a direct performance benefit is still unclear.

Bolus Ingestion of Whey Protein Immediately Post-Exercise Does Not Influence Rehydration Compared to Energy-Matched Carbohydrate Ingestion

Whey protein is a commonly ingested nutritional supplement amongst athletes and regular exercisers; however, its role in post-exercise rehydration remains unclear. Eight healthy male and female participants completed two experimental trials involving the ingestion of 35 g of whey protein (WP) or maltodextrin (MD) at the onset of a rehydration period, followed by ingestion of water to a volume equivalent to 150% of the amount of body mass lost during exercise in the heat. The gastric emptying rates of the solutions were measured using ¹³C breath tests. Recovery was monitored for a further 3 h by the collection of blood and urine samples. The time taken to empty half of the initial solution (T_1/2) was different between the trials (WP = 65.5 ± 11.4 min; MD = 56.7 ± 6.3 min; p = 0.05); however, there was no difference in cumulative urine volume throughout the recovery period (WP = 1306 ± 306 mL; MD = 1428 ± 443 mL; p = 0.314). Participants returned to net negative fluid balance 2 h after the recovery period with MD and 3 h with WP. The results of this study suggest that whey protein empties from the stomach at a slower rate than MD; however, this does not seem to exert any positive or negative effects on the maintenance of fluid balance in the post-exercise period.

Protein and the Adaptive Response With Endurance Training: Wishful Thinking or a Competitive Edge?

The significance of carbohydrates for endurance training has been well established, whereas the role of protein and the adaptive response with endurance training is unclear. Therefore, the aim of this perspective is to discuss the current evidence on the role of dietary protein and the adaptive response with endurance training. On a metabolic level, a single bout of endurance training stimulates the oxidation of several amino acids. Although the amount of amino acids as part of total energy expenditure during exercise is relatively low compared to other substrates (e.g., carbohydrates and fat), it may depress the rates of skeletal muscle protein synthesis, and thereby have a negative effect on training adaptation. A low supply of amino acids relative to that of carbohydrates may also have negative effects on the synthesis of capillaries, synthesis and turn-over of mitochondrial proteins and proteins involved in oxygen transport including hamoglobin and myoglobin. Thus far, the scientific evidence demonstrating the significance of dietary protein is mainly derived from research with resistance exercise training regimes. This is not surprising since the general paradigm states that endurance training has insignificant effects on skeletal muscle growth. This could have resulted in an underappreciation of the role of dietary protein for the endurance athlete. To conclude, evidence of the role of protein on endurance training adaptations and performance remains scarce and is mainly derived from acute exercise studies. Therefore, future human intervention studies must unravel whether dietary protein is truly capable of augmenting endurance training adaptations and ultimately performance.

Skeletal muscle amino acid transporter and BCAT2 expression prior to and following interval running or resistance exercise in mode-specific trained males

Endurance (END)- and resistance (RES)-trained males performed interval running or resistance exercise during three consecutive days (bouts 1-3). Muscle biopsies were obtained at baseline, 2 h post-bout 1, and 72 h post-bout 3. Amino acid transporter SNAT2 mRNA was 75% greater in END (group p = 0.008), and increased ~ 70% 2 h post in both groups (time p = 0.023). Amino acid transporter PAT1 mRNA was 2.7-fold greater in RES (group p = 0.002). Baseline protein levels of the mitochondrial aminotransferase BCAT2 were 79% greater in END (p = 0.015).

Post-Game High Protein Intake May Improve Recovery of Football-Specific Performance during a Congested Game Fixture: Results from the PRO-FOOTBALL Study

The effects of protein supplementation on performance recovery and inflammatory responses during a simulated one-week in-season microcycle with two games (G1, G2) performed three days apart were examined. Twenty football players participated in two trials, receiving either milk protein concentrate (1.15 and 0.26 g/kg on game and training days, respectively) (PRO) or an energy-matched placebo (1.37 and 0.31 g/kg of carbohydrate on game and training days, respectively) (PLA) according to a randomized, repeated-measures, crossover, double-blind design. Each trial included two games and four daily practices. Speed, jump height, isokinetic peak torque, and muscle soreness of knee flexors (KF) and extensors (KE) were measured before G1 and daily thereafter for six days. Blood was drawn before G1 and daily thereafter. Football-specific locomotor activity and heart rate were monitored using GPS technology during games and practices. The two games resulted in reduced speed (by 3–17%), strength of knee flexors (by 12–23%), and jumping performance (by 3–10%) throughout recovery, in both trials. Average heart rate and total distance covered during games remained unchanged in PRO but not in PLA. Moreover, PRO resulted in a change of smaller magnitude in high-intensity running at the end of G2 (75–90 min vs. 0–15 min) compared to PLA (P = 0.012). KE concentric strength demonstrated a more prolonged decline in PLA (days 1 and 2 after G1, P = 0.014–0.018; days 1, 2 and 3 after G2, P = 0.016–0.037) compared to PRO (days 1 after G1, P = 0.013; days 1 and 2 after G2, P = 0.014–0.033) following both games. KF eccentric strength decreased throughout recovery after G1 (PLA: P=0.001–0.047—PRO: P =0.004–0.22) in both trials, whereas after G2 it declined throughout recovery in PLA (P = 0.000–0.013) but only during the first two days (P = 0.000–0.014) in PRO. No treatment effect was observed for delayed onset of muscle soreness, leukocyte counts, and creatine kinase activity. PRO resulted in a faster recovery of protein and lipid peroxidation markers after both games. Reduced glutathione demonstrated a more short-lived reduction after G2 in PRO compared to PLA. In summary, these results provide evidence that protein feeding may more efficiently restore football-specific performance and strength and provide antioxidant protection during a congested game fixture.