Metabolic factors in fatigue

The impact of task (un)certainty on repeated grip force production

Many studies found that in physical tasks, reducing certainty regarding their endpoints hinders performance. However, the impact of reducing certainty regarding other aspects of physical tasks is unknown. Here we manipulated the certainty of the required effort on an unrelated, parallel task (i.e., off-task uncertainty) and examined how it impacts force production in two within-subject experiments (N = 79). In two sessions, subjects completed 20 repetitions composed of maximal forces using a gripper with their dominant hand. Between repetitions, participants applied either submaximal constant or varied grip forces, with their non-dominant arm, matched for total forces across repetitions. While we observed trivial differences in total forces between conditions, under the varied condition, participants produced a steeper decrease in forces, suggesting that off-task uncertainty impacted their effort allocation strategy. We speculate that this pattern can be attributed to cognitive overload and/or changes in motivation stemming from the imposed uncertainty.

Effect of active recovery using individual maximum exercise capacity: a pilot study

[Purpose] The intensity of active recovery (AR) for performance recovery is often determined using breath gas analyzers and other special equipment. However, such procedures are difficult to perform in the field or where facilities are inadequate. Although several AR methods using simple patient-derived information have been proposed, only a few have specifically addressed their immediate effects. The present study aimed to quantify the immediate effects of AR, which was determined using the maximum exercise capacity calculated using a physical fitness test without specialized devices. [Participants and Methods] Thirty-two healthy male participants were equally divided into AR and control groups. Each group performed squat jumps, followed by a recovery intervention of jogging at a set intensity in the AR group or rest in a seated position in the control group. Standing long jumps performed before and after the squat jumps as well as after the intervention were analyzed. [Results] The recovery rate for standing long jumps was significantly higher in the AR group than in the control group. [Conclusion] The results of this pilot study indicate that the implementation of AR based on maximum exercise capacity may enhance performance recovery and requires further validation in larger studies.

Chronic Administration of Exogenous Lactate Increases Energy Expenditure during Exercise through Activation of Skeletal Muscle Energy Utilization Capacity in Mice

We compared the effects of chronic exogenous lactate and exercise training, which influence energy substrate utilization and body composition improvements at rest and during exercise, and investigated the availability of lactate as a metabolic regulator. The mice were divided into four groups: CON (sedentary + saline), LAC (sedentary + lactate), EXE (exercise + saline), and EXLA (exercise + lactate). The total experimental period was set at 4 weeks, the training intensity was set at 60-70% VO2max, and each exercise group was administered a solution immediately after exercise. Changes in the energy substrate utilization at rest and during exercise, the protein levels related to energy substrate utilization in skeletal muscles, and the body composition were measured. Lactate intake and exercise increased carbohydrate oxidation as a substrate during exercise, leading to an increased energy expenditure and increased protein levels of citrate synthase and malate dehydrogenase 2, key factors in the TCA(tricarboxylic acid) cycle of skeletal muscle. Exercise, but not lactate intake, induced the upregulation of the skeletal muscle glucose transport factor 4 and a reduction in body fat. Hence, chronic lactate administration, as a metabolic regulator, influenced energy substrate utilization by the skeletal muscle and increased energy expenditure during exercise through the activation of carbohydrate metabolism-related factors. Therefore, exogenous lactate holds potential as a metabolic regulator.

Fatigue as hallmark of Fabry disease: role of bioenergetic alterations

Fabry disease (FD) is a lysosomal storage disorder due to the impaired activity of the α-galactosidase A (GLA) enzyme which induces Gb3 deposition and multiorgan dysfunction. Exercise intolerance and fatigue are frequent and early findings in FD patients, representing a self-standing clinical phenotype with a significant impact on the patient's quality of life. Several determinants can trigger fatigability in Fabry patients, including psychological factors, cardiopulmonary dysfunctions, and primary alterations of skeletal muscle. The "metabolic hypothesis" to explain skeletal muscle symptoms and fatigability in Fabry patients is growing acknowledged. In this report, we will focus on the primary alterations of the motor system emphasizing the role of skeletal muscle metabolic disarrangement in determining the altered exercise tolerance in Fabry patients. We will discuss the most recent findings about the metabolic profile associated with Fabry disease offering new insights for diagnosis, management, and therapy.

The relationship between fatigue and sickness absence from work

Background

Although many studies have been conducted on worker fatigue and sickness absence, the association between fatigue and sickness absence is unclear in Korean workers. This study was conducted to investigate the effect of worker fatigue on future sickness absence.

Methods

The study was conducted on workers who received medical check-ups at a university hospital for two consecutive years (2014-2015). During check-ups in the first year, the Fatigue Severity Scale (FSS) was used to assess fatigue levels, and during check-ups in the second year, sickness absence was surveyed to determine whether they had been absent from work due to physical or mental illness during previous 12 months. The χ2 test was used to analyze relationships between sociodemographic and occupational characteristics, fatigue levels, and sickness absence. Odds ratios (ORs) were calculated by logistic regression analysis controlled for confounding factors.

Results

A total of 12,250 workers were included in the study, and 396 (3.2%) workers experienced more than one day of sickness absence during the study period. Adjusted ORs for sickness absence were 3.35 (95% confidence interval [CI]: 2.64-4.28) in the moderate-fatigue group and 6.87 (95% CI: 4.93-9.57) in the high-fatigue group versus the low-fatigue group. For men in the moderate- and high-fatigue groups, adjusted ORs for sickness absence were 3.40 (95% CI: 2.58-4.48) and 8.94 (95% CI: 6.12-13.07), and for women in the moderate- and high-fatigue groups, adjusted ORs for sickness absence were 2.93 (95% CI: 1.68-5.10) and 3.71 (95% CI: 1.84-7.49), respectively.

Conclusions

Worker fatigue is associated with sickness absence during the following 12 months, and this association appears to be stronger for men than women. These results support the notion that sickness absence can be reduced by evaluating and managing work-related fatigue.

The role of exercise and hypoxia on glucose transport and regulation

Muscle glucose transport activity increases with an acute bout of exercise, a process that is accomplished by the translocation of glucose transporters to the plasma membrane. This process remains intact in the skeletal muscle of individuals with insulin resistance and type 2 diabetes mellitus (T2DM). Exercise training is, therefore, an important cornerstone in the management of individuals with T2DM. However, the acute systemic glucose responses to carbohydrate ingestion are often augmented during the early recovery period from exercise, despite increased glucose uptake into skeletal muscle. Accordingly, the first aim of this review is to summarize the knowledge associated with insulin action and glucose uptake in skeletal muscle and apply these to explain the disparate responses between systemic and localized glucose responses post-exercise. Herein, the importance of muscle glycogen depletion and the key glucoregulatory hormones will be discussed. Glucose uptake can also be stimulated independently by hypoxia; therefore, hypoxic training presents as an emerging method for enhancing the effects of exercise on glucose regulation. Thus, the second aim of this review is to discuss the potential for systemic hypoxia to enhance the effects of exercise on glucose regulation.

Positive Effects of Pre-exercise Metabolic Alkalosis on Perceived Exertion and Post-exercise Squat Jump Performance in World-Class Cyclists

ABSTRACT

Thomas, C, Delfour-Peyrethon, R, Dorel, S, and Hanon, C. Positive effects of pre-exercise metabolic alkalosis on perceived exertion and post-exercise squat jump performance in world-class cyclists. J Strength Cond Res 36(9): 2602-2609, 2022-This study aimed to determine the effects of pre-exercise alkalosis in world-class cyclists on their general (rate of perceived exertion [RPE]) and local (category-ratio scale [CR10]) perceived rates of exertion and acid-base status during 2 types of training sessions. Eight world-class cyclists ingested either sodium bicarbonate (BIC) or a placebo (PLA) in a double-blind and randomized order before performing 4 × 1,000 m constant-power sprints (CP) or 3 × 500 m all-out sprints (AO), with 20 minutes of recovery time between each session. For AO, the performance was assessed through the cycling sprint velocity and a squat jump test during recovery. During both tests, RPE, CR10, and acid-base status were measured. Sodium bicarbonate ingestion was effective in inducing pre-exercise alkalosis, compared with a PLA ( p < 0.05). During CP, performance and RPE were the same for BIC and PLA ( p > 0.05) with no time effect. The CR10 increased for the last sprint in PLA ( p < 0.05) but was attenuated in BIC (BIC: 6 vs. PLA: 8.2; p < 0.05), whereas there was no difference in acid-base status. During AO, RPE and CR10 increased with time, with no BIC effect, whereas blood lactate concentration was different ( p < 0.05). Sodium bicarbonate supplementation had no effect on overall repeated sprints ( p > 0.05). However, world-class athletes responded to BIC with higher squat jump performance than the PLA condition after AO ( p < 0.05). Our results suggest a positive influence of pre-exercise alkalosis in world-class cyclists on local perception of efforts after constant load sprints and an attenuation of muscle power output decline postsprint, as evidenced by improved squat jump performance after all-out cycling effort.

Psychiatric medication and physical performance parameters - Are there implications for treatment?

INTRODUCTION

The impact of psychiatric medications and their enhancing or impairing effects on physical performance remains inconclusive. Therefore, with this systematic review we provide a comprehensive overview of frequently used psychotropic drugs and their effects on physical performance for the purpose of providing empirical information and deriving prescription and therapy recommendations for clinical practice.

METHODS

We systematically searched PubMed, PsycInfo, and Cochrane databases and extracted human studies investigating the effect of psychotropic drugs on parameters associated with the level of physical performance, such as exercise time, oxygen consumption, heart rate, muscle contraction or blood lactate concentration in physically healthy participants. 36 studies - comprising a broad range of psychotropic agents, such as antidepressants, antipsychotics, sedatives, and stimulants - were selected for final analyses.

RESULTS

Most studies (N = 32) were randomized controlled trials (RCT) with a double-blind crossover design. Antidepressants (N = 21) were the most frequently studied drug class, with contradictory results e.g., performance enhancement in warm environment but not in temperate conditions for bupropion or inconsistent findings between studies for other antidepressants. Antipsychotics (N = 3) mainly showed impairing effects on physical performance, while stimulants (N = 4) were often performance-enhancing. Sedatives (N = 9) may cause a hangover effect.

CONCLUSION

The examined studies with heterogeneous design showed different effects of psychiatric medications on physical performance. Antipsychotics seemed to be performance impairing, while the findings for antidepressants and sedatives were more inconsistent. Stimulants were the only group with consistent performance-enhancing effects. However, most studies were conducted with a small sample size (N < 10), mostly in well-trained subjects rather than in patients with psychiatric disorders, and most studies used single-dose designs. These issues impede the formulation of generalized conclusions for treatment regimes and should therefore be considered in further longitudinal studies for clinically reliable statements. Nevertheless, answering our research question is quite relevant for clinical practice and therapeutic prescription and should be further investigated especially considering the high drop-out rates in drug treatment.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=276103], identifier [CRD42021276103].

Acute Administration of Exogenous Lactate Increases Carbohydrate Metabolism during Exercise in Mice

In this study, we investigated the effects of exogenous lactate administration before exercise on energy substrate utilization during exercise. Mice were divided into exercise control (EX) and exercise with lactate intake (EXLA) groups; saline/lactate was administered 30 min before exercise. Respiratory gas was measured during moderate intensity treadmill exercise (30 min). Immediately after exercise, blood, liver, and skeletal muscle samples were collected and mRNA levels of energy metabolism-related and metabolic factors were analyzed. At 16–30 min of exercise, the respiratory exchange ratio (p = 0.045) and carbohydrate oxidation level (p = 0.014) were significantly higher in the EXLA than in the EX group. Immediately after exercise, the muscle and liver glycogen content and blood glucose level of the EXLA group were lower than those of the EX group. In addition, muscle mRNA levels of HK2 (hexokinase 2; p = 0.009), a carbohydrate oxidation-related factor, were higher in the EXLA than in the EX group, whereas the expression of PDK4 (pyruvate dehydrogenase kinase 4; p = 0.001), CS (citrate synthase; p = 0.045), and CD36 (cluster of differentiation 36; p = 0.002), factors related to oxidative metabolism, was higher in the EX than in the EXLA group. These results suggest that lactate can be used in various research fields to promote carbohydrate metabolism.

Immediate and Delayed Effects of Cupping Therapy on Reducing Neuromuscular Fatigue

Cupping therapy has been popular in elite athletes in recent years. However, the effect of cupping therapy on reducing muscle fatigue has not been investigated. The purpose of this study was to investigate the immediate and delayed effects of cupping therapy on reducing biceps brachii fatigue during biceps curls. Twelve healthy untrained participants were recruited for this repeated-measures study. Cupping therapy (–300 mmHg pressure for 5 min) and sham control (no negative pressure for 5 min) were applied after biceps fatigue induced by performing repeated biceps curls at 75% of the 10 repetitions of maximum of the non-dominant hand. Surface electromyography (EMG) with spectral analyses [mean frequency (MNF), median frequency (MDF), and spectral moments ratio (SMR)] were used to assess muscle fatigue during the fatigue task. EMG signals during the first 10 repetitions and the last 10 repetitions of biceps curls were used to assess neuromuscular fatigue. There were significant decreases in MNF and MDF and a significant increase in SMR immediately and 24 h after the sham control (no intervention). When comparing the MNF, MDF, and SMR after cupping therapy to the sham control, there was no significant immediate effect on reducing muscle fatigue. However, there was a significant delayed effect on improving recovery following fatigue for the cupping therapy compared to the sham control (MNF changes: sham 0.87 ± 0.02 vs. cupping 0.91 ± 0.02, p < 0.05; MDF changes sham: 0.85 ± 0.03 vs. cupping: 0.91 ± 0.02, p < 0.05; SMR changes: sham 1.89 ± 0.15 vs. cupping 1.58 ± 0.13, p < 0.05). The findings of this study demonstrate that there is a time effect of cupping therapy for reducing muscle fatigue. Cupping therapy is effective on reducing biceps brachii muscle fatigue after 24 h.

Multinuclear MRS at 7T Uncovers Exercise Driven Differences in Skeletal Muscle Energy Metabolism Between Young and Seniors

Purpose: Aging is associated with changes in muscle energy metabolism. Proton (¹H) and phosphorous (³¹P) magnetic resonance spectroscopy (MRS) has been successfully applied for non-invasive investigation of skeletal muscle metabolism. The aim of this study was to detect differences in adenosine triphosphate (ATP) production in the aging muscle by ³¹P-MRS and to identify potential changes associated with buffer capacity of muscle carnosine by ¹H-MRS.

Methods: Fifteen young and nineteen elderly volunteers were examined. ¹H and ³¹P-MRS spectra were acquired at high field (7T). The investigation included carnosine quantification using ¹H-MRS and resting and dynamic ³¹P-MRS, both including saturation transfer measurements of phosphocreatine (PCr), and inorganic phosphate (Pi)-to-ATP metabolic fluxes.

Results: Elderly volunteers had higher time constant of PCr recovery (τ_PCr) in comparison to the young volunteers. Exercise was connected with significant decrease in PCr-to-ATP flux in both groups. Moreover, PCr-to-ATP flux was significantly higher in young compared to elderly both at rest and during exercise. Similarly, an increment of Pi-to-ATP flux with exercise was found in both groups but the intergroup difference was only observed during exercise. Elderly had lower muscle carnosine concentration and lower postexercise pH. A strong increase in phosphomonoester (PME) concentration was observed with exercise in elderly, and a faster Pi:PCr kinetics was found in young volunteers compared to elderly during the recovery period.

Conclusion: Observations of a massive increment of PME concentration together with high Pi-to-ATP flux during exercise in seniors refer to decreased ability of the muscle to meet the metabolic requirements of exercise and thus a limited ability of seniors to effectively support the exercise load.

Clinical massage therapy for patients with exercise-induced fatigue: A protocol for systematic review and meta analysis

BACKGROUND

Exercise-induced fatigue (EF) has been a major area of interest within the field of sports and clinical medicine. Implemented on people's skin, muscles, and joints as an important part of complementary and alternative medicine , massage therapy has a positive effect on the recovery of EF and sports injuries. In this systematic review, we aim to evaluate the effectiveness and safety of massage therapy for patients with EF.

METHODS

We will search the following electronic databases for randomized controlled trials to evaluate the effectiveness and safety of massage therapy in treating EF: China National Knowledge Infrastructure, Wanfang and PubMed Database, Cochrane Central Register of Controlled Trials, Cumulative Index of Nursing and Allied Health Literature, Excerpta Medica database, and Medical Literature Analysis and Retrieval System Online. Each database will be searched from inception to May 2020. The entire process will include study selection, data extraction, risk of bias assessment and meta-analyses.

RESULTS

This proposed study will evaluate the effectiveness and safety of massage therapy for patients with EF. The outcomes will include change in fatigue relief and adverse effect.

CONCLUSIONS

This proposed systematic review will evaluate the existing evidence on the effectiveness and safety of massage therapy for patients with EF.

DISSEMINATION AND ETHICS

The results of this review will be disseminated through peer-reviewed publication. Because all of the data used in this systematic review and meta-analysis has been published, this review does not require ethical approval. Furthermore, all data will be analyzed anonymously during the review process.

Influence of Interval Training Frequency on Time-Trial Performance in Elite Endurance Athletes

PURPOSE

To determine the impact of interval training frequency in elite endurance athletes. It was hypothesized that two longer sessions would elicit greater performance improvements and physiological adaptation than four shorter sessions at the same intensity.

METHODS

Elite cross-country skiers and biathletes were randomly assigned to either a high-frequency group (HF group) (5 M, 1 F, age 22 (19-26), VO_2max 67.8 (65.5-70.2) mL/kg/min) doing four short interval sessions per week or a low-frequency group (LF group) (8 M, 1 F, age 22 (18-23), VO_2max 70.7 (67.0-73.9) mL/kg/min) doing two longer interval sessions. All interval sessions were performed at ~85% of maximum heart rate, and groups were matched for total weekly training volume. Pre- and post-intervention, athletes completed an 8 km rollerski time-trial, maximal oxygen uptake (VO_2max) test, and an incremental, submaximal exercise test.

RESULTS

The LF group had a statistically significant improved time-trial performance following the intervention (p = 0.04), with no statistically significant changes in the HF group. Similarly, percentage utilization of VO_2max at anaerobic threshold (p = 0.04) and exercise economy (p = 0.01) were statistically significantly improved following the intervention in the LF group only. No statistically significant changes in VO_2max were observed in either group.

CONCLUSIONS

Two longer interval sessions appear superior to four shorter sessions per week in promoting endurance adaptations and performance improvements in elite endurance athletes. Despite matched training volume and exercise intensity, the larger, more concentrated exercise stimulus in the LF group appears to induce more favorable adaptations. The longer time between training sessions in the LF group may also have allowed athletes to recover more effectively and better "absorb" the training. These findings are in line with the "best practice" observed by many of the world's best endurance athletes.

Pre-Exercise Glucose Ingestion May Improve Endurance Capacity in East Asian Student Athletes with Lower Blood Glucose Response

The main purpose of this study was to investigate the influence of pre-exercise glucose ingestion after a 2.5-h fast on the endurance capacity and blood glucose response in East Asian athletes who is expected to have genetically low insulin response. A total of 8 Japanese student athletes ingested 1.5 g/kg body mass of glucose (G trial) or 0.5 g/kg body mass of artificial sweetener dissolved in water (P trial) 30 min before exercise test after consuming a standardized breakfast. The exercise test comprised 40 min cycling exercise at 50% maximal oxygen uptake (VO_2max), immediately followed by cycling to exhaustion at 70% VO_2max. Before analyzing the data, we grouped the subjects into two groups depending on whether they showed rapid increase in blood glucose at the onset of exercise (increase rate in LOW group is <20% and HIGH group is ≥20%) to evaluate subject's insulin response to glucose feeding. No subjects developed rebound hypoglycemia (<70 mg/dL) in the G trial of both group. Significantly higher blood glucose during exercise was recognized only in the G trial of LOW group. Although no significant difference was observed between the two trials of both group, cycling time to exhaustion in the LOW group tended to increase because of glucose ingestion. These results suggest that pre-exercise ingestion of glucose in East Asian student athletes does not induce rebound hypoglycemia regardless of difference in individual insulin responses. Furthermore, individuals with low insulin responses seem to improve endurance performance with glucose ingestion before exercise.

DETERMINATION OF INDIVIDUAL GLUCOSE THRESHOLD USING PHARMACY PORTABLE BLOOD GLUCOSE METER

ABSTRACT Introduction The individual glucose threshold (IGT) has been used to estimate the anaerobic threshold with low-cost analyses and shorter times. However, the reliability of the glycemic analysis using a portable pharmacy glucose meter has received little attention. Objective To identify the IGT using a portable glucose meter and to compare it with the ventilatory threshold (VT). Methods Fourteen active, healthy men (25.9 ± 3.2 years; %BF = 17.9 ± 3.7%) performed an incremental treadmill test. The anaerobic threshold was identified by two different methods: (1) IGT, corresponding to the intensity of the lowest glucose value during the test; and (2) VT, corresponding to the break in linearity of the ventilation curve and an increase in the respiratory oxygen equivalent, without an equivalent increase in carbon dioxide. Results There were significant differences between VT (9.9 ± 1.2 km/h) and IGT (9.5 ± 1/1 km/h), corresponding to 75.4 ± 9.2 and 72.5 ± 10.4 %VO2max, respectively. The methods presented high correlation (r = 0.82, p = 0.002) and the Bland-Altman technique showed agreement between IGT and VT, with a mean difference of 0.5 km/h. Conclusion It was possible to determine the intensity of IGT by the glycemic response in the incremental test using a portable glucose meter. The IGT underestimated the intensity of VT by approximately 0.5 km/h, but with a high correlation and agreement between them. Level of evidence III, Case-Controle Study.

Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers

Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large fraction of this power, and high running/walking economy. Nutrition-related contributors include body mass and anthropometry, capacity to use fuels, particularly carbohydrate (CHO) to produce adenosine triphosphate economically over the duration of the event, and maintenance of reasonable hydration status in the face of sweat losses induced by exercise intensity and the environment. Race nutrition strategies include CHO-rich eating in the hours per days prior to the event to store glycogen in amounts sufficient for event fuel needs, and in some cases, in-race consumption of CHO and fluid to offset event losses. Beneficial CHO intakes range from small amounts, including mouth rinsing, in the case of shorter events to high rates of intake (75-90 g/hr) in the longest races. A personalized and practiced race nutrition plan should balance the benefits of fluid and CHO consumed within practical opportunities, against the time, cost, and risk of gut discomfort. In hot environments, prerace hyperhydration or cooling strategies may provide a small but useful offset to the accrued thermal challenge and fluid deficit. Sports foods (drinks, gels, etc.) may assist in meeting training/race nutrition plans, with caffeine, and, perhaps nitrate being used as evidence-based performance supplements.

Exercise and Cardioprotection: A Natural Defense Against Lethal Myocardial Ischemia-Reperfusion Injury and Potential Guide to Cardiovascular Prophylaxis

Similar to ischemic preconditioning, high-intensity exercise has been shown to decrease infarct size following myocardial infarction. In this article, we review the literature on beneficial effects of exercise, exercise requirements for cardioprotection, common methods utilized in laboratories to study this phenomenon, and discuss possible mechanisms for exercise-mediated cardioprotection.

Effects of nine weeks L-Carnitine supplementation on exercise performance, anaerobic power, and exercise-induced oxidative stress in resistance-trained males

[Purpose]

Studies of L-carnitine in healthy athletic populations have yielded equivocal results. Further scientific-based knowledge is needed to clarify the ability of L-carnitine to improve exercise capacity and expedite the recovery process by reducing oxidative stress. This study aimed to examine the 9-week effects of L-carnitine supplementation on exercise performance, anaerobic capacity, and exercise-induced oxidative stress markers in resistance-trained males.

[Methods]

In a double-blind, randomized, and placebo-controlled treatment, 23 men (age, 25±2y; weight, 81.2±8.31 kg; body fat, 17.1±5.9%) ingested either a placebo (2 g/d, n=11) or L-carnitine (2 g/d, n=12) for 9 weeks in conjunction with resistance training. Primary outcome measurements were analyzed at baseline and at weeks 3, 6, and 9. Participants underwent a similar resistance training (4 d/w, upper/lower body split) for a 9-week period. Two-way ANOVA with repeated measures was used for statistical analysis.

[Results]

There were significant increases in bench press lifting volume at wk-6 (146 kg, 95% CI 21.1, 272) and wk-9 (245 kg, 95% CI 127, 362) with L-carnitine. A similar trend was observed for leg press. In the L-carnitine group, at wk-9, there were significant increases in mean power (63.4 W, 95% CI 32.0, 94.8) and peak power (239 W, 95% CI 86.6, 392), reduction in post-exercise blood lactate levels (-1.60 mmol/L, 95% CI -2.44, -0.75) and beneficial changes in total antioxidant capacity (0.18 mmol/L, 95% CI 0.07, 0.28).

[Conclusion]

L-carnitine supplementation enhances exercise performance while attenuating blood lactate and oxidative stress responses to resistance training.

Energetics of male field-sport athletes during the 3-min all-out test for linear and shuttle-based running

PURPOSE

All-out, non-steady state running makes for difficult comparisons regarding linear and shuttle running; yet such differences remain an important distinction for field-based sports. The purpose of the study was to determine whether an energetic approach could be used to differentiate all-out linear from shuttle running.

METHODS

Fifteen male field-sport athletes volunteered for the study (means ± SD): age, 21.53 ± 2.23 years; height, 1.78 ± 0.68 m; weight, 83.85 ± 11.73 kg. Athletes completed a graded exercise test, a 3-min linear all-out test and two all-out shuttle tests of varied distances (25 m and 50 m shuttles).

RESULTS

Significant differences between the all-out tests were found for critical speed (CS) [F(8.97), p < 0.001), D' (finite capacity for running speeds exceeding critical speed) [F(7.83), p = 0.001], total distance covered [F(85.31), p < 0.001], peak energetic cost ([Formula: see text]) [F(45.60), p < 0.001], peak metabolic power ([Formula: see text]) [F(23.36), p < 0.001], average [Formula: see text] [F(548.74), p < 0.001], maximal speed [F(22.87), p < 0.001] and fatigue index [F(3.93), p = 0.027]. Non-significant differences were evident for average [Formula: see text] [F(2.47), p = 0.097], total [Formula: see text] [F(0.86), p = 0.416] and total [Formula: see text] [F(2.11), p = 0.134].

CONCLUSIONS

The energetic approach provides insights into performance characteristics that differentiate linear from shuttle running, yet surprising similarities between tests were evident. Key parameters from all-out linear and shuttle running appear to be partly interchangeable between tests, indicating that the final choice between linear and shuttle testing should be based on the requirements of the sport.

Effects of Synergist vs. NonSynergist Split Resistance Training Routines on Acute Neuromuscular Performance in Resistance-Trained Men

Castanheira, RPM, Ferreira-Junior, JB, Celes, RS, Rocha-Junior, VA, Cadore, EL, Izquierdo, M, and Bottaro, M. Effects of synergist vs. nonsynergist split resistance training routines on acute neuromuscular performance in resistance-trained men. J Strength Cond Res 31(12): 3482-3488, 2017-The aim of this study was to evaluate the effects of synergist (SN) vs. nonsynergist (NS) split resistance training routines on the acute neuromuscular performance of the elbow flexors in resistance-trained men. Fifteen resistance-trained men (age: 23.2 ± 4.0 years, height: 173.0 ± 0.08 cm, and body mass: 78.38 ± 9.31 kg) randomly performed 3 training routines separated by an interval of 7 days: (a) pull-pull exercises (SN), which included 6 sets of 10 repetition maximum (RM) of a seated row exercise followed by 4 sets of 10RM of the preacher biceps curl exercise; (b) push-pull exercises (NS), which included 6 sets of 10RM of the bench press exercise followed by 4 sets of 10RM of the preacher biceps curl exercise; and (c) Control, which included 4 sets of 10RM of the preacher biceps curl exercise. Elbow flexors peak torque, total work, and the amplitude of electromyography signal (EMG root mean square) were measured during the elbow flexor isokinetic exercise. Peak torque was 10.2 and 3.9% higher during Control condition when compared with the SN and NS conditions, respectively (p ≤ 0.05). Peak torque was also 6.0% greater in the NS condition than the SN condition (p ≤ 0.05). Moreover, total work was 5.1% greater in the NS condition than the SN condition. Additionally, EMG findings did not differ among conditions (p > 0.05). In conclusion, a push and pull NS split routine is recommended to maximize elbow flexor training performance (i.e., lower acute loading effect) in trained subjects.

Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial

BACKGROUND

Low-carbohydrate, ketogenic diets cause mild, subclinical systemic acidosis. Anaerobic exercise performance is limited by acidosis. Therefore, we evaluated the hypothesis that a low-carbohydrate, ketogenic diet impairs anaerobic exercise performance, as compared to a high-carbohydrate diet.

METHODS

Sixteen men and women (BMI, 23±1 kg/m2, age 23±1 years) participated in a randomized-sequence, counterbalanced crossover study in which they underwent exercise testing after 4 days of either a low-carbohydrate, ketogenic diet (LC; <50 g/day and <10% of energy from carbohydrates) or a high-carbohydrate diet (HC; 6-10 g/kg/day carbohydrate). Dietary compliance was assessed with nutrient analysis of diet records, and with measures of urine pH and ketones. Anaerobic exercise performance was evaluated with the Wingate anaerobic cycling test and the yo-yo intermittent recovery test.

RESULTS

The diets were matched for total energy (LC: 2333±158 kcal/d; HC: 2280±160 kcal/d; P=0.65) but differed in carbohydrate content (9±1% vs. 63±2% of energy intake; P<0.001). LC resulted in lower urine pH (5.9±0.1 vs. 6.3±0.2, P=0.004) and the appearance of urine ketones in every participant. LC resulted in 7% lower peak power (801±58 watts vs. 857±61 watts, P=0.008) and 6% lower mean power (564±50 watts vs. 598±51 watts, P=0.01) during the Wingate Test. Total distance ran in the yo-yo intermittent recovery test was 15% less after LC diet (887±139 vs. 1045±145 meters, P=0.02).

CONCLUSIONS

Short-term low-carbohydrate, ketogenic diets reduce exercise performance in activities that are heavily dependent on anaerobic energy systems. These findings have clear performance implications for athletes, especially for high-intensity, short duration activities and sports.

Performance during a strenuous swimming session is associated with high blood lactate: pyruvate ratio and hypoglycemia in fasted rats

The aim of this study was to investigate the effect of lactatemia elevation and glycemia reduction on strenuous swimming performance in fasted rats. Three rats were placed in a swimming tank at the same time. The first rat was removed immediately (control group) and the remaining ones were submitted to a strenuous swimming session. After the second rat was exhausted (Exh group), the third one was immediately removed from the water (Exe group). According to the period of time required for exhaustion, the rats were divided into four groups: low performance (3–7 min), low-intermediary performance (8–12 min), high-intermediary performance (13–17 min), and high performance (18–22 min). All rats were removed from the swimming tanks and immediately killed by decapitation for blood collection or anesthetized for liver perfusion experiments. Blood glucose, lactate, and pyruvate concentrations, blood lactate/pyruvate ratio, and liver lactate uptake and its conversion to glucose were evaluated. Exhaustion in low and low-intermediary performance were better associated with higher lactate/pyruvate ratio. On the other hand, exhaustion in high-intermediary and high performance was better associated with hypoglycemia. Lactate uptake and glucose production from lactate in livers from the Exe and Exh groups were maintained. We concluded that there is a time sequence in the participation of lactate/pyruvate ratio and hypoglycemia in performance during an acute strenuous swimming section in fasted rats. The liver had an important participation in preventing hyperlactatemia and hypoglycemia during swimming through lactate uptake and its conversion to glucose.

A double-blind pilot study of the effect of Prokarin™ on fatigue in multiple sclerosis

In this 12-week study with 29 subjects, the effect of Prokarin™ (n =22), a proprietary blend of histamine and caffeine, was compared to placebo group (n=7) for the following outcomes: 1) fatigue as measured by the Modified Fatigue Impact Scale (MFIS); 2) lower limb function as measured by timed walk test; 3) upper limb function as measured by the pegboard test; 4) cognitive function as measured by the Paced Auditory Serial Additions Test (PASAT); 5) serum caffeine level; 6) change in brain chemistry as measured by quantitative magnetic resonance spectroscopy assay of N-acetyl aspartate (NAA); and 7) safety as measured by routine blood chemistry, TSH and urinalysis. Data were acquired at baseline, 4, 8 and 12 weeks. The Prokarin™ group MFIS mean was significantly different from the mean of the placebo group at 12 weeks (df=24, t=2.08, P=<0.02), with respective means of 37.40, SD=15.18, for the Prokarin™ group and 53.2, SD=11.39 for the controls. For the secondary endpoints (PASAT, 25 foot timed walk, peg test, and magnetic resonance spectroscopy [MRS]), there were no significant differences between the Prokarin™-treated group and the placebo group. However, there were significant improvements within the Prokarin™ group for each of these measures for the pre- versus posttreatment comparison at 12 weeks. Serum caffeine data indicated that caffeine exerted no independent effect on performance. No laboratory abnormalities were seen, and the treatment was well tolerated. Conclusion: There was a modest-size statistical effect of Prokarin ™ on fatigue in multiple sclerosis (MS) compared with the placebo group. A larger trial is warranted, based on this pilot study. Multiple Sclerosis (2002) 8, 30-35

Technical Alterations during an Incremental Field Test in Elite Male Tennis Players

PURPOSE

We investigated technical and physiological responses along with their relationships during an incremental field test to exhaustion specific to tennis (TEST) in elite players.

METHODS

Twenty male elite tennis players completed TEST, which consisted of hitting alternatively forehand and backhand strokes at increasing ball frequency (ball machine) every minute. Ball accuracy (BA), ball velocity (BV), and tennis performance (TP) index (TP = BA × BV) were determined by radar and video analysis for each stroke, in addition to cardiorespiratory responses and blood lactate concentrations.

RESULTS

At low intensities (less than 80% of maximal oxygen uptake [V˙O2max]), technical performance was steady. From 80% to 100% of V˙O2max, significant and steady decreases in BV (-9.0% and -13.3%; P = 0.02 and P = 0.002), BA (-19.4% and -18.4%; both P < 0.001), and TP (-27.4% and -29.15%; both P = 0.002) occurred for forehands and backhands, respectively. Changes in TP and blood lactate concentration from 60% to 100% of V˙O2max were inversely correlated (r = -0.51, P = 0.008). BV was 5.2% higher (P = 0.042) for forehand versus backhand, and there was no difference between strokes for both BA (P = 0.930) and TP (P = 0.536).

CONCLUSION

Technical alterations (i.e., decrease in BV, BA, and TP) in elite players undergoing TEST only occurred at high intensity (>80% of V˙O2max), presumably because of the use of compensatory strategies to overcome fatigue. Above this intensity, all technical indices decreased steadily until exhaustion, independently of the stroke nature.

The Effect of Interchange Rotation Period and Number on Australian Football Running Performance

Montgomery, PG, and Wisbey, B. The effect of interchange rotation period and number on Australian Football running performance. J Strength Cond Res 30(7): 1890-1897, 2016-To determine the effect of on-field rotation periods and total number of game rotations on Australian Football running performance, elite Australian Football players (n = 21, mean ± SD; 23.2 ± 1.7 years; 183.5 ± 3.7 cm; 83.2 ± 4.5 kg) had Global Positioning System game data from 22 rounds divided into a total of 692 on-field playing periods. These periods were allocated into time blocks of 2:00-minute increments, with the log transformed percentage differences in running performance (m·min) between blocks analyzed by effect size and meaningful differences. A total of 7,730 game rotation and associated average m·min combinations collected over 3 Australian Football seasons were also assessed by effect size and meaningful differences. Running capacity decreases after 5:00 minutes by ∼3% for each 2:00 minutes of on-field time up to 9:00 minutes, with variable responses between positions up to 6.7% for nomadic players. For each rotation less than 6 per game, clear small-to-moderate decreases up to 3.6% in running capacity occurred per rotation. To maintain a high level of running capacity, shorter on-field periods are more effective in Australian Football; however, players and coaches should be aware that with interchange restriction, slightly longer on-field periods achieve similar results.

Nutritional Strategies to Modulate Intracellular and Extracellular Buffering Capacity During High-Intensity Exercise

Intramuscular acidosis is a contributing factor to fatigue during high-intensity exercise. Many nutritional strategies aiming to increase intra- and extracellular buffering capacity have been investigated. Among these, supplementation of beta-alanine (~3–6.4 g/day for 4 weeks or longer), the rate-limiting factor to the intramuscular synthesis of carnosine (i.e. an intracellular buffer), has been shown to result in positive effects on exercise performance in which acidosis is a contributing factor to fatigue. Furthermore, sodium bicarbonate, sodium citrate and sodium/calcium lactate supplementation have been employed in an attempt to increase the extracellular buffering capacity. Although all attempts have increased blood bicarbonate concentrations, evidence indicates that sodium bicarbonate (0.3 g/kg body mass) is the most effective in improving high-intensity exercise performance. The evidence supporting the ergogenic effects of sodium citrate and lactate remain weak. These nutritional strategies are not without side effects, as gastrointestinal distress is often associated with the effective doses of sodium bicarbonate, sodium citrate and calcium lactate. Similarly, paresthesia (i.e. tingling sensation of the skin) is currently the only known side effect associated with beta-alanine supplementation, and it is caused by the acute elevation in plasma beta-alanine concentration after a single dose of beta-alanine. Finally, the co-supplementation of beta-alanine and sodium bicarbonate may result in additive ergogenic gains during high-intensity exercise, although studies are required to investigate this combination in a wide range of sports.

Association of physical performance and biochemical profile of mice with intrinsic endurance swimming

We aimed to investigate the potential mediators and relationship affecting congenital exercise performance in an animal model with physical activity challenge from physiological and biochemical perspectives. A total of 75 male ICR mice (5 weeks old) were adapted for 1 week, then mice performed a non-loading and exhaustive swimming test and were assigned to 3 groups by exhaustive swimming time: low exercise capacity (LEC) (<3 hr), medium exercise capacity (MEC) (3-5 hr), and high exercise capacity (HEC) (>5 hr). After a 1-week rest, the 3 groups of mice performed an exhaustive swimming test with a 5% and 7.5% weight load and a forelimb grip-strength test, with a 1-week rest between tests. Blood samples were collected immediately after an acute exercise challenge and at the end of the experiment (resting status) to evaluate biochemical blood variables and their relation with physical performance. Physical activity, including exhaustive swimming and grip strength, was greater for HEC than other mice. The swimming performance and grip strength between groups were moderately correlated (r=0.443, p<0.05). Resting serum ammonium level was moderately correlated with endurance with a 7.5% weight load (r=-0.447, p<0.05) and with lactate level (r=0.598, p<0.05). The pulmonary morphology of the HEC group seemed to indicate benefits for aerobic exercise. Mice showed congenital exercise performance, which was significantly correlated with different physical challenges and biochemical variable values. This study may have implications for interference in intrinsic characteristics.

Expression of ammonia transporters Rhbg and Rhcg in mouse skeletal muscle and the effect of 6-week training on these proteins

The purposes of our study were to examine (1) Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg) expressions in mouse skeletal muscle; and (2) the effect of 6-week training on Rhbg and Rhcg expressions. The levels of Rhbg and Rhcg expressions were much higher in the soleus (Sol) than in the plantaris (Pla) or gastrocnemius (Gas). Immunofluorescence microscopy demonstrated that Rhbg colocalizes with dystrophin, a plasma membrane protein marker, whereas Rhcg colocalizes with CD31, a vascular endothelial cell marker. In a 6-week swim training study, we set up two different training groups. Endurance (END) group underwent swim training without load for 30 min and exercise time was increased by 30 min every 2 weeks. High-intensity interval training (HIIT) group underwent 10–12 sets of swim training at 20 sec per set and intervals of 10 sec, with a load of 10% body weight. After 6 weeks of training, all mice performed exhaustive swimming performance test (PT), with 9% of body weight to exhaustion. HIIT group could significantly swim more and showed significantly lower blood ammonia level compared with control (CON) group at immediately after PT. Rhbg and Rhcg levels did not change after 6 weeks in both END and HIIT groups. Our results indicate that ammonia transporters are more abundant in slow fiber than fast fiber muscles and 6 weeks swim training suppresses blood ammonia elevation induced by high-intensity exercise with performance improvement, although the levels of ammonia transporter proteins does not change.

Monitoring training load to understand fatigue in athletes

Many athletes, coaches, and support staff are taking an increasingly scientific approach to both designing and monitoring training programs. Appropriate load monitoring can aid in determining whether an athlete is adapting to a training program and in minimizing the risk of developing non-functional overreaching, illness, and/or injury. In order to gain an understanding of the training load and its effect on the athlete, a number of potential markers are available for use. However, very few of these markers have strong scientific evidence supporting their use, and there is yet to be a single, definitive marker described in the literature. Research has investigated a number of external load quantifying and monitoring tools, such as power output measuring devices, time-motion analysis, as well as internal load unit measures, including perception of effort, heart rate, blood lactate, and training impulse. Dissociation between external and internal load units may reveal the state of fatigue of an athlete. Other monitoring tools used by high-performance programs include heart rate recovery, neuromuscular function, biochemical/hormonal/immunological assessments, questionnaires and diaries, psychomotor speed, and sleep quality and quantity. The monitoring approach taken with athletes may depend on whether the athlete is engaging in individual or team sport activity; however, the importance of individualization of load monitoring cannot be over emphasized. Detecting meaningful changes with scientific and statistical approaches can provide confidence and certainty when implementing change. Appropriate monitoring of training load can provide important information to athletes and coaches; however, monitoring systems should be intuitive, provide efficient data analysis and interpretation, and enable efficient reporting of simple, yet scientifically valid, feedback.

Effect of body composition on respiratory compensation point during an incremental test

Body mass (BM) and composition are considered to be significant determinants of aerobic endurance. The purpose of this study was to examine the influence of BM and its composition makeup on endurance performance. Thirty-nine men were divided into 3 groups of significantly different BM and mass composition: a control group, a group with high body fat (HBF), and a group with high lean body mass (HLBM). Participants in the HBF and HLBM groups had similar BM, which was significantly greater than observed in the control group. All participants performed an incremental treadmill test to volitional failure. Endurance performance was assessed on the basis of respiratory compensation point (RCP). The HBF and HLBM groups exceeded RCP at a much lower work intensity, expressed as %HRmax and %VO2max, compared with the control group. When considered relative to BM and lean body mass, oxygen consumption values at RCP were significantly less in the HBF and HLBM groups compared with the control group. Increased BM, regardless of its composition, substantially reduced aerobic endurance performance. Therefore, athletes and coaches should pay attention to not only the percentage of body fat but also to the amount of lean body mass because any gain may adversely affect aerobic endurance performance.

Effects of 28 days of beta-alanine and creatine supplementation on muscle carnosine, body composition and exercise performance in recreationally active females

BACKGROUND

The purpose of this study was to examine the short-term and chronic effects of β-ALA supplementation with and without creatine monohydrate on body composition, aerobic and anaerobic exercise performance, and muscle carnosine and creatine levels in college-aged recreationally active females.

METHODS

Thirty-two females were randomized in a double-blind, placebo-controlled manner into one of four supplementation groups: β-ALA only (BA, n = 8), creatine only (CRE, n = 8), β-ALA and creatine combined (BAC, n = 9) and placebo (PLA, n = 7). Participants supplemented for four weeks included a loading phase for the creatine for week 1 of 0.3 g/kg of body weight and a maintenance phase for weeks 2-4 of 0.1 g/kg of body weight, with or without a continuous dose of β-ALA of 0.1 g/kg of body weight with doses rounded to the nearest 800 mg capsule providing an average of 6.1 ± 0.7 g/day of β-ALA. Participants reported for testing at baseline, day 7 and day 28. Testing sessions consisted of obtaining a resting muscle biopsy of the vastus lateralis, body composition measurements, performing a graded exercise test on the cycle ergometer for VO2peak with lactate threshold determination, and multiple Wingate anaerobic capacity tests.

RESULTS

Although mean changes were consistent with prior studies and large effect sizes were noted, no significant differences were observed among groups in changes in muscle carnosine levels (BA 35.3 ± 45; BAC 42.5 ± 99; CRE 0.72 ± 27; PLA 13.9 ± 44%, p = 0.59). Similarly, although changes in muscle phosphagen levels after one week of supplementation were consistent with prior reports and large effect sizes were seen, no statistically significant effects were observed among groups in changes in muscle phosphagen levels and the impact of CRE supplementation appeared to diminish during the maintenance phase. Additionally, significant time × group × Wingate interactions were observed among groups for repeated sprint peak power normalized to bodyweight (p = 0.02) and rate of fatigue (p = 0.04).

CONCLUSIONS

Results of the present study did not reveal any consistent additive benefits of BA and CRE supplementation in recreationally active women.

An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease

BACKGROUND

Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications.

PURPOSE

The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD.

METHODS

An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological approach was consistent with ATS standards.

RESULTS

We identified important advances in our understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD. Since the last update, landmark studies were published on the mechanisms of development of limb muscle dysfunction in COPD and on the treatment of this condition. We now have a better understanding of the clinical implications of limb muscle dysfunction. Although exercise training is the most potent intervention to address this condition, other therapies, such as neuromuscular electrical stimulation, are emerging. Assessment of limb muscle function can identify patients who are at increased risk of poor clinical outcomes, such as exercise intolerance and premature mortality.

CONCLUSIONS

Limb muscle dysfunction is a key systemic consequence of COPD. However, there are still important gaps in our knowledge about the mechanisms of development of this problem. Strategies for early detection and specific treatments for this condition are also needed.

Assessment of the upper body contribution to multiple-sprint cycling in men and women

The aim of this study was to investigate the effect of repeated cycling sprints on power profiles while assessing upper body muscle contraction. Eighteen physically active participants performed 8 × 10 s repeated sprints while muscle activity was recorded via surface electromyography (sEMG) from the brachioradialis (BR), biceps brachii (BB), triceps brachii (TB) and upper trapezius (UT). Measurements were obtained at rest, during a functional maximum contraction (FMC) while participants were positioned in a seated position on the cycle ergometer and during the repeated sprint protocol. Results suggest that mainly type I muscle fibres (MFs) are being recruited within the upper body musculature due to the submaximal and intermittent nature of the contractions. Subsequently, there is no evidence of upper body fatigue across the sprints, which is reflected in the lack of changes in the median frequency of the power spectrum (P<0·05).

Hyperlactemia induction modes affect the lactate minimum power and physiological responses in cycling

The aim of this study was to verify the influence of hyperlactemia and blood acidosis induction on lactate minimum intensity (LMI). Twenty recreationally trained males who were experienced in cycling (15 cyclists and 5 triathletes) participated in this study. The athletes underwent 3 lactate minimum tests on an electromagnetic cycle ergometer. The hyperlactemia induction methods used were graded exercise test (GXT), Wingate test (WAnT), and 2 consecutive Wingate tests (2 × WAnTs). The LMI at 2 × WAnTs (200.3 ± 25.8 W) was statistically higher than the LMI at GXT (187.3 ± 31.9 W) and WAnT (189.8 ± 26.0 W), with similar findings for blood lactate, oxygen uptake, and pulmonary ventilation at LMI. The venous pH after 2 × WAnTs was lower (7.04 ± 0.24) than in (p ≤ 0.05) the GXT (7.19 ± 0.05) and WAnT (7.19 ± 0.05), whereas the blood lactate response was higher. In addition, similar findings were observed for bicarbonate concentration [HCO3] (2 × WAnTs lower than WAnT; 15.3 ± 2.6 mmol·L and 18.2 ± 2.7 mmol·L1, respectively) (p ≤ 0.05). However, the maximal aerobic power and total time measured during the incremental phase also did not differ. Therefore, we can conclude that the induction mode significantly affects pH, blood lactate, and [HCO3] and consequently they alter the LMI and physiological parameters at LMI.

Importance of muscle power variables in repeated and single sprint performance in soccer players

This study examined the relationship between lower body power and repeated as well as single sprint performance in soccer players. The performance of nineteen male soccer players was examined. The first testing session included the countermovement jump (CMJL) and the progressive full squat (FSL), both with external loads. Power in the CMJL and FSL was measured with each load that was lifted. The second session included a protocol of 40-m repeated sprints with a long recovery period (2 min). The number of sprints executed until there was a 3% decrease in performance for the best 40-m sprint time was recorded as a repeated sprint index (RSI). The RSI was moderately associated with power output relative to body mass in the CMJL and FSL (r = 0.53/0.54, p ≤ 0.05). The most and least powerful players (determined by FSL) showed significant differences in the RSI (9.1 ± 4.2 vs. 6.5 ± 1.6) and 10 m sprint time (p ± 0.01). Repeated and single sprints are associated with relatively lower body power in soccer players.

Liver hydrolysate assists in the recovery from physical fatigue in a mouse model

It is reported that liver hydrolysate (LH) enhances liver function. However, the effects of LH on physical fatigue are unknown. The aim of this study was to investigate the effect of LH on alterations in locomotor activity and energy metabolism such as 5'-AMP-activated protein kinase (AMPK), glycogen content, and blood lactic acid, after forced walking. Adult male ddY mice were used. Locomotor activity, AMPK phosphorylation, and glycogen content in the liver and soleus muscle, as well as blood lactic acid were determined following LH treatment before and/or after forced walking. The locomotor activity significantly decreased after forced walking for 3 h. Two administrations of LH (30 or 100 mg/kg) significantly increased the locomotor activity, while a single administration either before or after forced walking did not show any specific effect. Administering LH twice activated AMPK in the liver and soleus muscle. Glycogen levels significantly decreased in both the liver and soleus muscle after forced walking, whereas the blood lactate level significantly increased. In contrast, administering LH twice increased muscle glycogen and decreased blood lactic acid. These findings indicate that LH produced an anti-fatigue effect and that this effect appears to involve the efficient glycogen utilization through activation of AMPK.

Influência da aptidão aeróbia no running anaerobic sprint test (RAST)

O objetivo do estudo foi verificar a possível influência de diferentes níveis de aptidão aeróbia (VO2MAX) sobre os parâmetros do running anaerobic sprint test (RAST). Para isso, 38 indivíduos (Idade = 18,1±2,5 anos, Estatura = 173±1 cm e Massa corporal = 65,1±6,5 kg) foram classificados em dois grupos, baixa e elevada aptidão aeróbias (GBA: n=22 e GEA: n=16). O VO2MAX foi determinado por um esforço incremental em esteira rolante até a exaustão voluntária. O RAST foi composto de seis esforços máximos de 35m separados por 10s de intervalo passivo. O VO2MAX foi significativamente diferente entre os grupos (GBA = 51,7±1,9 mL.kg-1.min-1; GEA = 58,6±3,1 mL.kg-1.min-1). A potência média (PM) foi significativamente superior no grupo GBA (552,7±132,1 W) em relação ao grupo GEA (463,6±132,8 W). O impulso (ImP) foi significativamente correlacionado com o VO2MAX no GEA. Pode-se concluir que há um indicativo que o metabolismo aeróbio exerce uma influência na realização do RAST.

The kinetics of lactate production and removal during whole-body exercise

BACKGROUND

Based on a literature review, the current study aimed to construct mathematical models of lactate production and removal in both muscles and blood during steady state and at varying intensities during whole-body exercise. In order to experimentally test the models in dynamic situations, a cross-country skier performed laboratory tests while treadmill roller skiing, from where work rate, aerobic power and blood lactate concentration were measured. A two-compartment simulation model for blood lactate production and removal was constructed.

RESULTS

The simulated and experimental data differed less than 0.5 mmol/L both during steady state and varying sub-maximal intensities. However, the simulation model for lactate removal after high exercise intensities seems to require further examination.

CONCLUSIONS

Overall, the simulation models of lactate production and removal provide useful insight into the parameters that affect blood lactate response, and specifically how blood lactate concentration during practical training and testing in dynamical situations should be interpreted.

Effects of citrulline supplementation on fatigue and exercise performance in mice

During high-intensity exercise, the concentration of ammonia is augmented in skeletal muscle. Ammonia activates phosphofructokinase and prevents oxidation of pyruvate to acetyl CoA, thus leading to exhaustion. Citrulline is an amino acid component of the urea cycle in the liver, along with ornithine and arginine. The aim of this study was to examine the effect of citrulline supplementation on fatigue and performance during high-intensity exercise. We constructed a swimming exercise protocol, in which mice were subjected to exhaustive swimming with a load of 5% body weight, and measured the time until exhaustion, the blood levels of lactate and ammonia, and the glycogen content of the gastrocnemius and biceps femoris muscles. Citrulline supplementation significantly increased the swimming time until exhaustion. Exercise-induced blood ammonia elevation was repressed by citrulline supplementation, and exercise-induced blood lactate increment in the citrulline-supplemented group was significantly lower than that in the non-supplemented group. Citrulline supplementation may facilitate the detoxification of ammonia via the urea cycle and inhibit additional glycolysis. Our findings suggest that citrulline supplementation may be useful for improving the exercise performance of athletes.

Effects of acute and chronic exercise on sarcolemmal MCT1 and MCT4 contents in human skeletal muscles: current status

Two lactate/proton cotransporter isoforms (monocarboxylate transporters, MCT1 and MCT4) are present in the plasma (sarcolemmal) membranes of skeletal muscle. Both isoforms are symports and are involved in both muscle pH and lactate regulation. Accordingly, sarcolemmal MCT isoform expression may play an important role in exercise performance. Acute exercise alters human MCT content, within the first 24 h from the onset of exercise. The regulation of MCT protein expression is complex after acute exercise, since there is not a simple concordance between changes in mRNA abundance and protein levels. In general, exercise produces greater increases in MCT1 than in MCT4 content. Chronic exercise also affects MCT1 and MCT4 content, regardless of the initial fitness of subjects. On the basis of cross-sectional studies, intensity would appear to be the most important factor regulating exercise-induced changes in MCT content. Regulation of skeletal muscle MCT1 and MCT4 content by a variety of stimuli inducing an elevation of lactate level (exercise, hypoxia, nutrition, metabolic perturbations) has been demonstrated. Dissociation between the regulation of MCT content and lactate transport activity has been reported in a number of studies, and changes in MCT content are more common in response to contractile activity, whereas changes in lactate transport capacity typically occur in response to changes in metabolic pathways. Muscle MCT expression is involved in, but is not the sole determinant of, muscle H(+) and lactate anion exchange during physical activity.

Effect of expertise on postmaximal long sprint blood metabolite responses

The aim of this study was to describe and compare the blood metabolic responses obtained after a single maximal exercise in elite and less-successful athletes and to investigate whether these responses are related to sprint performance. Eleven elite (ELI) and 14 regional (REG) long sprint runners performed a 300-m running test as fast as possible. Blood samples were taken at rest and at 4 minutes after exercise for measurements of blood lactate concentration [La] and acid-base status. The blood metabolic responses of ELI subjects compared to those of REG subjects for pH (7.07 ± 0.05 vs. 7.14 ± 1.5), sodium bicarbonate concentration ([HCO(3)(-)], 8.1 ± 1.5 vs. 9.8 ± 1.8 mmol·L(-1)), hemoglobin O(2) saturation (SaO(2)) (94.7 ± 1.8 vs. 96.2 ± 1.6%) were significantly lower (p < 0.05), and [La] was significantly higher in ELI (21.1 ± 2.9 vs. 19.1 ± 1.2 mmol·L(-1), p < 0.05). The 300-m performance (in % world record) was negatively correlated with pH (r = -0.55, p < 0.01), SaO2 (r = -0.64, p < 0.001), [HCO(3)(-)] (r = -0.40, p < 0.05), and positively correlated with [La] (r = 0.44, p < 0.05). In conclusion, for the same quantity of work, the best athletes are able to strongly alter their blood acid-base balance compared to underperforming runners, with larger acidosis and lactate accumulation. To obtain the pH limits with acute maximal exercise, coaches must have their athletes perform a distance run with duration of exercise superior to 35 seconds. The blood lactate accumulation values (mmol·L(-1)·s(-1)) recorded in this study indicate that the maximal glycolysis rate obtained in the literature from short sprint distances is maintained, but not increased, until 35 seconds of exercise.

Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans

We have previously shown that insulin increases muscle total carnitine (TC) content during acute i.v. l-carnitine infusion. Here we determined the effects of chronic l-carnitine and carbohydrate (CHO; to elevate serum insulin) ingestion on muscle TC content and exercise metabolism and performance in humans. On three visits, each separated by 12 weeks, 14 healthy male volunteers (age 25.9 ± 2.1 years, BMI 23.0 ± 0.8 kg m−2) performed an exercise test comprising 30 min cycling at 50% , 30 min at 80% , then a 30 min work output performance trial. Muscle biopsies were obtained at rest and after exercise at 50% and 80% on each occasion. Following visit one, volunteers ingested either 80 g of CHO (Control) or 2 g of l-carnitine-l-tartrate and 80 g of CHO (Carnitine) twice daily for 24 weeks in a randomised, double blind manner. All significant effects reported occurred after 24 weeks. Muscle TC increased from basal by 21% in Carnitine (P < 0.05), and was unchanged in Control. At 50% , the Carnitine group utilised 55% less muscle glycogen compared to Control (P < 0.05) and 31% less pyruvate dehydrogenase complex (PDC) activation compared to before supplementation (P < 0.05). Conversely, at 80% , muscle PDC activation was 38% higher (P < 0.05), acetylcarnitine content showed a trend to be 16% greater (P < 0.10), muscle lactate content was 44% lower (P < 0.05) and the muscle PCr/ATP ratio was better maintained (P < 0.05) in Carnitine compared to Control. The Carnitine group increased work output 11% from baseline in the performance trial, while Control showed no change. This is the first demonstration that human muscle TC can be increased by dietary means and results in muscle glycogen sparing during low intensity exercise (consistent with an increase in lipid utilisation) and a better matching of glycolytic, PDC and mitochondrial flux during high intensity exercise, thereby reducing muscle anaerobic ATP production. Furthermore, these changes were associated with an improvement in exercise performance.