The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review

The effect of the ketogenic diet on resistance training load management: a repeated-measures clinical trial in trained participants

BACKGROUND

The effect of low-carbohydrate high-fat dietary manipulation, such as the ketogenic diet (KD), on muscle strength assessment in resistance-training (RT) participants has focused on the one-repetition maximum test (1-RM). However, a pre-specified 1-RM value during an exercise training program disregards several confounding factors (i.e. sleep, diet, and training-induced fatigue) that affect the exerciser's "true" load and daily preparedness. We aimed to evaluate the effect of a 6-week RT program on load control-related variables in trained subjects following a KD intervention.

METHODS

Fourteen resistance-trained individuals (3F, 11 M; 30.1 [6.2] years; 174.2 [7.6] cm; 75.7 [10.8] kg; BMI 24.8 [2.1] kg·m-2) completed this single-arm repeated-measures clinical trial. Load management variables included volume load, number of repetitions, perceived exertion (RPE), movement velocity loss, and exertion index. These primary outcomes were assessed weekly before, during, and at the end of a 6-week RT program that included traditional RT exercises (bench press, femoral lying down, lat pulldown, leg extension, and back squat).

RESULTS

There was a significant difference in RPE between weeks (p = 0.015, W = 0.19) with a slight trend in decreasing RPE. We found differences in the volume load per week (p < 0.001; W = 0.73 and p < 0.001, W = 0.81, respectively), with an increase in the last weeks. In the control of the load based on movement velocity, we did not find significant differences between weeks (p = 0.591, W = 0.06), although significant differences were found in the effort index (p = 0.026, W = 0.17).

CONCLUSIONS

A KD diet in recreational strength participants does not appear to lead to performance losses during a RT program aimed at improving body composition. However, the lack of adherence and familiarity with the ketogenic diet must be considered specially during first weeks.

Effect of acute meal and long-term intake of a Mediterranean Diet providing different amounts of carbohydrates on physical performance and biomarkers in non-professional strength athletes

The study aims to evaluate the effect of an acute meal and long-term intake of Mediterranean Diet (MD) on different parameters such as strength, physical performance, body composition and blood markers in a group of non-professional athletes who practice a strength activity. Thirteen volunteers completed two 8-week dietary interventions in a randomised, cross-over design. Also an acute study was performed. Subjects received a MD High in carbohydrates, characterised by at least five portions of pasta/week and an average 55-60% of daily energy derived from carbohydrates, versus an MD reduced in carbohydrates, with less than two portions of pasta/week and an average of 40-45% of daily energy provided by carbohydrates. Mainly, data did not show significant differences for the parameters analysed, except for Elbow Flexor maximum voluntary contraction (p = .039). Results enlighten that increasing total carbohydrates intake, as typically in the MD, does not negatively affect physical performance, body composition and strength.

Accuracy of a continuous glucose monitoring system applied before, during, and after an intense leg-squat session with low- and high-carbohydrate availability in young adults without diabetes

PURPOSE

The aim was to assess the accuracy of a continuous blood glucose monitoring (CGM) device (Abbott FreeStyle Libre 3) against capillary blood glucose measurement (BGM) before, during, and after an intense lower body strength training session in connection with high- versus low-carbohydrate breakfasts.

METHODS

Nine adults (22 ± 2 years) completed a strength training session (10 × 10 at 60% 1RM) twice after high-carbohydrate and twice after low-carbohydrate breakfasts. CGM accuracy versus BGM was assessed across four phases: post-breakfast, pre-exercise, exercise, and post-exercise.

RESULTS

Overall fed state mean BGM levels were 84.4 ± 20.6 mg/dL. Group-level Bland-Altman analysis showed acceptable agreement between CGM and BGM across all phases, with mean biases between - 7.95 and - 17.83 mg/dL; the largest discrepancy was in the post-exercise phase. Mean absolute relative difference was significantly higher post-exercise compared to pre-exercise and exercise phases, for overall data and after the high-carbohydrate breakfast (all p ≤ 0.02). Clark Error Grid analysis showed 50.5-64.3% in Zone A and 31.7-44.6% in Zone B, with an increase in treatment errors during and after exercise.

CONCLUSION

In this group of healthy participants undergoing strength training, CGM showed satisfactory accuracy in glucose monitoring but varied substantially between individuals compared to BGM and fails in meeting clinical criteria for diabetic monitoring. CGM could aid non-diabetic athletes by tracking glucose fluctuations due to diet and exercise. Although utilization of CGM shows potential in gathering, analyzing, and interpreting interstitial glucose for improving performance, the application in sports nutrition is not yet validated, and challenges in data interpretation could limit its adoption.

Effects of the Ketogenic Diet on Strength Performance in Trained Men and Women: A Systematic Review and Meta-Analysis

Ketogenic diets (KDs) are an alternative to improve strength performance and body composition in resistance training participants. The objective of this review and meta-analysis is to verify whether a ketogenic diet produces an increase in the strength of resistance-trained participants. We have evaluated the effect of the ketogenic diet in conjunction with resistance training on the strength levels in trained participants. Boolean algorithms from various databases (PubMed, Scopus, and Web of Science) were used. Meta-analyses were carried out, one on the 1-RM squat (SQ), with 106 trained participants or athletes, and another on the 1-RM on the bench press (BP), evaluating 119 participants. We did not find significant differences between the groups in the variables of SQ or BP, although the size of the effect was slightly higher in the ketogenic group. Conclusions: KDs do not appear to impair 1-RM performance; however, this test does not appear to be the most optimal tool for assessing hypertrophy-based strength session performance in resistance-trained participants.

Acute Effects of 30 g Cyclodextrin Intake during CrossFit® Training on Performance and Fatigue

The main objective of this study was to investigate the influence of carbohydrate intake (cyclodextrin) on performance during the performance of two consecutive workouts of the day (WODs) lasting 20 min each. Twenty-one male CrossFit (CF) athletes (29.5 ± 4.3 years; 72.81 ± 12.85 kg; 1.74 ± 0.06 m; 3.41 ± 1.21 years of experiences) participated in a crossover, randomized, and double-blind study. The effect of supplementation with 30 g of cyclodextrin (SG) (Cluster Dextrin®) or placebo (PG) (Bolero Advanced Hydration®) was evaluated on the performance of two specific WOD. Additionally, the effect on handgrip maximum strength, countermovement jump (CMJ), Wingate test, and 1 RM bench press test was evaluated. The effect on blood glucose and lactate was also evaluated. No differences were found in time, height, and power (W/Kg) in CMJ. However, there was a percentage improvement in CMJ jump power (W) (p < 0.05) between the groups, assuming an improvement in performance due to the intervention. Moreover, both conditions experimented differences in execution speed between sets (p < 0.05) in pre-WOD, and differences in post-WOD only in the placebo group, as well as decreases in this variable per repetition across the set (p < 0.01) in both conditions. However, no differences were found in the rest of the variables. Supplementation with 30 g of cyclodextrin did not have any metabolic or performance effects in CF tests. Although some differences between groups were observed in CMJ and power tests for bench press, the data are not conclusive and further research is needed in this regard.

Athletes' nutritional demands: a narrative review of nutritional requirements

Nutrition serves as the cornerstone of an athlete's life, exerting a profound impact on their performance and overall well-being. To unlock their full potential, athletes must adhere to a well-balanced diet tailored to their specific nutritional needs. This approach not only enables them to achieve optimal performance levels but also facilitates efficient recovery and reduces the risk of injuries. In addition to maintaining a balanced diet, many athletes also embrace the use of nutritional supplements to complement their dietary intake and support their training goals. These supplements cover a wide range of options, addressing nutrient deficiencies, enhancing recovery, promoting muscle synthesis, boosting energy levels, and optimizing performance in their respective sports or activities. The primary objective of this narrative review is to comprehensively explore the diverse nutritional requirements that athletes face to optimize their performance, recovery, and overall well-being. Through a thorough literature search across databases such as PubMed, Google Scholar, and Scopus, we aim to provide evidence-based recommendations and shed light on the optimal daily intakes of carbohydrates, protein, fats, micronutrients, hydration strategies, ergogenic aids, nutritional supplements, and nutrient timing. Furthermore, our aim is to dispel common misconceptions regarding sports nutrition, providing athletes with accurate information and empowering them in their nutritional choices.

Combined Exercise Training and Nutritional Interventions or Pharmacological Treatments to Improve Exercise Capacity and Body Composition in Chronic Obstructive Pulmonary Disease: A Narrative Review

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease that is associated with significant morbidity, mortality, and healthcare costs. The burden of respiratory symptoms and airflow limitation can translate to reduced physical activity, in turn contributing to poor exercise capacity, muscle dysfunction, and body composition abnormalities. These extrapulmonary features of the disease are targeted during pulmonary rehabilitation, which provides patients with tailored therapies to improve the physical and emotional status. Patients with COPD can be divided into metabolic phenotypes, including cachectic, sarcopenic, normal weight, obese, and sarcopenic with hidden obesity. To date, there have been many studies performed investigating the individual effects of exercise training programs as well as nutritional and pharmacological treatments to improve exercise capacity and body composition in patients with COPD. However, little research is available investigating the combined effect of exercise training with nutritional or pharmacological treatments on these outcomes. Therefore, this review focuses on exploring the potential additional beneficial effects of combinations of exercise training and nutritional or pharmacological treatments to target exercise capacity and body composition in patients with COPD with different metabolic phenotypes.

Improved physical performance of elite soccer players based on GPS results after 4 days of carbohydrate loading followed by 3 days of low carbohydrate diet

BACKGROUND

Carbohydrate loading is an established sports nutrition strategy for endur- 16 ance exercise performance. We tested if carbohydrate loading could improve the performance of 17 elite soccer players under ecologically valid circumstances using Global Positioning System (GPS) data.

METHODS

Twenty-two adult Iran Premier league soccer players were divided into a carbohydrate-loading group (CLG) and Control group (CG). The carbohydrate loading group restricted carbohydrate intake for three days to 1.5 g/kg/d while increasing exercise intensity. From days four to seven, exercise intensity was decreased and carbohydrate intake was considerably increased up to 7.5 g/kg/d on the day of the match, during which performance was analyzed using GPS data. The control group performed the same exercise training but maintained their habitual carbohydrate intake of 5-6 g/kg/d. The data were analyzed using a univariate ANCOVA with baseline data from a pre-intervention match as the control variable.

RESULTS

The carbohydrate loading team scored significantly higher on running distance, maximum speed and the number of top and repeated sprints; the carbohydrate loading group scored significantly lower on player load, metabolic power and running imbalance compared to the control team during their match.

CONCLUSIONS

Our findings suggest carbohydrate loading enabled elite soccer players to achieve greater running outputs with greater metabolic efficiency and lower fatigue compared to their habitual diets.

Monitoring Resistance Training in Real Time with Wearable Technology: Current Applications and Future Directions

Resistance training is an exercise modality that involves using weights or resistance to strengthen and tone muscles. It has become popular in recent years, with numerous people including it in their fitness routines to ameliorate their strength, muscle mass, and overall health. Still, resistance training can be complex, requiring careful planning and execution to avoid injury and achieve satisfactory results. Wearable technology has emerged as a promising tool for resistance training, as it allows monitoring and adjusting training programs in real time. Several wearable devices are currently available, such as smart watches, fitness trackers, and other sensors that can yield detailed physiological and biomechanical information. In resistance training research, this information can be used to assess the effectiveness of training programs and identify areas for improvement. Wearable technology has the potential to revolutionize resistance training research, providing new insights and opportunities for developing optimized training programs. This review examines the types of wearables commonly used in resistance training research, their applications in monitoring and optimizing training programs, and the potential limitations and challenges associated with their use. Finally, it discusses future research directions, including the development of advanced wearable technologies and the integration of artificial intelligence in resistance training research.

Low carbohydrate availability impairs hypertrophy and anaerobic performance

PURPOSE OF REVIEW

Highlight contemporary evidence examining the effects of carbohydrate restriction on the intracellular regulation of muscle mass and anaerobic performance.

RECENT FINDINGS

Low carbohydrate diets increase fat oxidation and decrease fat mass. Emerging evidence suggests that dietary carbohydrate restriction increases protein oxidation, thereby limiting essential amino acid availability necessary to stimulate optimal muscle protein synthesis and promote muscle recovery. Low carbohydrate feeding for 24 h increases branched-chain amino acid (BCAA) oxidation and reduces myogenic regulator factor transcription compared to mixed-macronutrient feeding. When carbohydrate restriction is maintained for 8 to 12 weeks, the alterations in anabolic signaling, protein synthesis, and myogenesis likely contribute to limited hypertrophic responses to resistance training. The blunted hypertrophic response to resistance training when carbohydrate availability is low does not affect muscle strength, whereas persistently low muscle glycogen does impair anaerobic output during high-intensity sprint and time to exhaustion tests.

SUMMARY

Dietary carbohydrate restriction increases BCAA oxidation and impairs muscle hypertrophy and anaerobic performance, suggesting athletes who need to perform high-intensity exercise should consider avoiding dietary strategies that restrict carbohydrate.

Glucose and Fructose Supplementation and Their Acute Effects on Anaerobic Endurance and Resistance Exercise Performance in Healthy Individuals: A Double-Blind Randomized Placebo-Controlled Crossover Trial

BACKGROUND

The effects of glucose, fructose and a combination of these on physical performance have been subject of investigation, resulting in diverse findings.

OBJECTIVE

The aim of this study was to investigate how an individualized amount of glucose, fructose, and a combination of these compared to placebo (sucralose) alter endurance performance on a cycle ergometer, lower and upper body resistance exercise performance at individualized thresholds in healthy young individuals.

METHODS

A total of 16 healthy adults (9 females) with an age of 23.8 ± 1.6 years and a BMI of 22.6 ± 1.8 kg/m² (body mass (BM) 70.9 ± 10.8 kg, height 1.76 ± 0.08 m) participated in this study. During the screening visit, the lactate turn point 2 (LTP2) was defined and the weights for chest-press and leg-press were determined. Furthermore, 30 min prior to each exercise session, participants received either 1 g/kg BM of glucose (Glu), 1 g/kg BM of fructose (Fru), 0.5 g/kg BM of glucose/fructose (GluFru) (each), or 0.2 g sucralose (placebo), respectively, which were dissolved in 300 mL of water. All exercises were performed until volitional exhaustion. Time until exhaustion (TTE) and cardio-pulmonary variables were determined for all cycling visits; during resistance exercise, repetitions until muscular failure were counted and time was measured. During all visits, capillary blood glucose and blood lactate concentrations as well as venous insulin levels were measured.

RESULTS

TTE in cycling was 449 ± 163 s (s) (Glu), 443 ± 156 s (Fru), 429 ± 160 s (GluFru) and 466 ± 162 s (Pla) (p = 0.48). TTE during chest-press sessions was 180 ± 95 s (Glu), 180 ± 92 s (Fru), 172 ± 78 s (GluFru) and 162 ± 66 s (Pla) (p = 0.25), respectively.

CONCLUSIONS

Pre-exercise supplementation of Glu, Fru and a combination of these did not have an ergogenic effect on high-intensity anaerobic endurance performance and on upper and lower body moderate resistance exercise in comparison to placebo.

Effects of the Ketogenic Diet on Muscle Hypertrophy in Resistance-Trained Men and Women: A Systematic Review and Meta-Analysis

Reviews focused on the ketogenic diet (KD) based on the increase in fat-free mass (FFM) have been carried out with pathological populations or, failing that, without population differentiation. The aim of this review and meta-analysis was to verify whether a ketogenic diet without programmed energy restriction generates increases in fat-free mass (FFM) in resistance-trained participants. We evaluated the effect of the ketogenic diet, in conjunction with resistance training, on fat-free mass in trained participants. Boolean algorithms from various databases (PubMed, Scopus. and Web of Science) were used, and a total of five studies were located that related to both ketogenic diets and resistance-trained participants. In all, 111 athletes or resistance-trained participants (87 male and 24 female) were evaluated in the studies analyzed. We found no significant differences between groups in the FFM variables, and more research is needed to perform studies with similar ketogenic diets and control diet interventions. Ketogenic diets, taking into account the possible side effects, can be an alternative for increasing muscle mass as long as energy surplus is generated; however, their application for eight weeks or more without interruption does not seem to be the best option due to the satiety and lack of adherence generated.

Protein O-GlcNAcylation in Metabolic Modulation of Skeletal Muscle: A Bright but Long Way to Go

O-GlcNAcylation is an atypical, dynamic and reversible O-glycosylation that is critical and abundant in metazoan. O-GlcNAcylation coordinates and receives various signaling inputs such as nutrients and stresses, thus spatiotemporally regulating the activity, stability, localization and interaction of target proteins to participate in cellular physiological functions. Our review discusses in depth the involvement of O-GlcNAcylation in the precise regulation of skeletal muscle metabolism, such as glucose homeostasis, insulin sensitivity, tricarboxylic acid cycle and mitochondrial biogenesis. The complex interaction and precise modulation of O-GlcNAcylation in these nutritional pathways of skeletal muscle also provide emerging mechanical information on how nutrients affect health, exercise and disease. Meanwhile, we explored the potential role of O-GlcNAcylation in skeletal muscle pathology and focused on its benefits in maintaining proteostasis under atrophy. In general, these understandings of O-GlcNAcylation are conducive to providing new insights into skeletal muscle (patho) physiology.

The Ergogenic Effects of Acute Carbohydrate Feeding on Resistance Exercise Performance: A Systematic Review and Meta-analysis

BACKGROUND

Carbohydrate (CHO) ingestion has an ergogenic effect on endurance training performance. Less is known about the effect of acute CHO ingestion on resistance training (RT) performance and equivocal results are reported in the literature.

OBJECTIVE

The current systematic review and meta-analysis sought to determine if and to what degree CHO ingestion influences RT performance.

METHODS

PubMed, MEDLINE, SportDiscus, Scopus, and CINAHL databases were searched for peer-reviewed articles written in English that used a cross-over design to assess the acute effect of CHO ingestion on RT performance outcomes (e.g., muscle strength, power, and endurance) in healthy human participants compared to a placebo or water-only conditions. The Cochrane Collaboration's risk of bias tool and GRADE approaches were used to assess risk of bias and certainty of evidence, respectively. Random effects meta-analyses were performed for total training session volume and post-exercise blood lactate and glucose. Sub-group meta-analysis and meta-regression were performed for categorical (session and fast durations) and continuous (total number of maximal effort sets, load used, and CHO dose) covariates, respectively.

RESULTS

Twenty-one studies met the inclusion criteria (n = 226 participants). Pooled results revealed a significant benefit of CHO ingestion in comparison to a placebo or control for total session training volume (standardised mean difference [SMD] = 0.61). Sub-group analysis revealed a significant benefit of CHO ingestion during sessions longer than 45 min (SMD = 1.02) and after a fast duration of 8 h or longer (SMD = 0.39). Pooled results revealed elevated post-exercise blood lactate (SMD = 0.58) and blood glucose (SMD = 2.36) with CHO ingestion. Meta-regression indicated that the number of maximal effort sets, but not CHO dose or load used, moderates the effect of CHO ingestion on RT performance (beta co-efficient [b] = 0.11). Carbohydrate dose does not moderate post-exercise lactate accumulation nor do maximal effort sets completed, load used, and CHO dose moderate the effect of CHO ingestion on post-exercise blood glucose.

CONCLUSIONS

Carbohydrate ingestion has an ergogenic effect on RT performance by enhancing volume performance, which is more likely to occur when sessions exceed 45 min and where the fast duration is ≥ 8 h. Further, the effect is moderated by the number of maximal effort sets completed, but not the load used or CHO dose. Post-exercise blood lactate is elevated following CHO ingestion but may come at the expense of an extended time-course of recovery due to the additional training volume performed. Post-exercise blood glucose is elevated when CHO is ingested during RT, but it is presently unclear if it has an impact on RT performance.

PROTOCOL REGISTRATION

The original protocol was prospectively registered on the Open Science Framework (Project identifier: https://doi.org/10.17605/OSF.IO/HJFBW ).