Skeletal muscle and erythrocyte redox status is associated with dietary cysteine intake and physical fitness in healthy young physically active men.

PURPOSE: To investigate the association between redox status in erythrocytes and skeletal muscle with dietary nutrient intake and markers of physical fitness and habitual physical activity (PA). METHODS: Forty-five young physically active men were assessed for body composition, dietary nutrient intake, muscle strength, cardiorespiratory capacity and habitual PA. Blood and muscle samples were collected to estimate selected redox biomarkers. Partial correlation analysis was used to evaluate the independent relationship of each factor with redox biomarkers. RESULTS: Dietary cysteine intake was positively correlated (p < 0.001) with both erythrocyte (r = 0.697) and muscle GSH (0.654, p < 0.001), erythrocyte reduced/oxidized glutathione ratio (GSH/GSSG) (r = 0.530, p = 0.001) and glutathione reductase (GR) activity (r = 0.352, p = 0.030) and inversely correlated with erythrocyte protein carbonyls (PC) levels (r = - 0.325; p = 0.046). Knee extensors eccentric peak torque was positively correlated with GR activity (r = 0.355; p = 0.031) while, one-repetition maximum in back squat exercise was positively correlated with erythrocyte GSH/GSSG ratio (r = 0.401; p = 0.014) and inversely correlated with erythrocyte GSSG and PC (r = - 0.441, p = 0.006; r = - 0.413, p = 0.011 respectively). Glutathione peroxidase (GPx) activity was positively correlated with step count (r = 0.520; p < 0.001), light (r = 0.406; p = 0.008), moderate (r = 0.417; p = 0.006), moderate-to-vigorous (r = 0.475; p = 0.001), vigorous (r = 0.352; p = 0.022) and very vigorous (r = 0.326; p = 0.035) PA. Muscle GSSG inversely correlated with light PA (r = - 0.353; p = 0.022). CONCLUSION: These results indicate that dietary cysteine intake may be a critical element for the regulation of glutathione metabolism and redox status in two different tissues pinpointing the independent significance of cysteine for optimal redox regulation. Musculoskeletal fitness and PA levels may be predictors of skeletal muscle, but not erythrocyte, antioxidant capacity. TRIAL REGISTRATION: Registry: ClinicalTrials.gov, identifier: NCT03711838, date of registration: October 19, 2018.

Extended Match Time Exacerbates Fatigue and Impacts Physiological Responses in Male Soccer Players.

PURPOSE: This study evaluated how extended match time (90 + 30 min) affected physiological responses and fatigue in male soccer players. METHODS: Twenty competitive players (mean ± SD: age, 20 ± 1 yr; maximal oxygen uptake, 59 ± 4 mL·min -1 ·kg -1 ) completed an experimental match with their activity pattern and heart rate assessed throughout the game, whereas countermovement jump performance and repeated sprint ability were tested and quadriceps muscle biopsies and venous blood samples were taken at baseline and after 90 and 120 min of match play. RESULTS: Less high-intensity running (12%) was performed in extra time in association with fewer intense accelerations and decelerations per minute compared with normal time. Peak sprint speed was 11% lower in extra time compared with normal time, and fatigue also manifested in impaired postmatch repeated sprint ability and countermovement jump performance (all P < 0.05). Muscle glycogen declined from 373 ± 59 mmol·kg -1 dry weight (dw) at baseline to 266 ± 64 mmol·kg -1 dw after 90 min, with a further decline to 186 ± 56 mmol·kg -1 dw after extra time ( P < 0.05) and with single-fiber analyses revealing depleted or very low glycogen levels in ~75% of both slow and fast twitch fibers. Blood glucose did not change during the first 90-min but declined ( P < 0.05) to 81 ± 8 mg·dL -1 after extra time. Plasma glycerol and ammonia peaked at 236 ± 33 mg·dL -1 and 75 ± 21 µmol·L -1 after the extra period. CONCLUSIONS: These findings demonstrate exacerbated fatigue after extra time compared with normal time, which seems to be associated with muscle glycogen depletion, reductions in blood glucose levels, and hyperammonemia. Together, this points to metabolic disturbances being a major part of the integrated and multifaceted fatigue response during extended soccer match play.

Effect of whey vs. soy protein supplementation on recovery kinetics following speed endurance training in competitive male soccer players: a randomized controlled trial.

BACKGROUND: Soccer-specific speed-endurance training induces short-term neuromuscular fatigue and performance deterioration over a 72-h recovery period, associated with elevated markers of exercise-induced muscle damage. We compared the effects of whey vs. soy protein supplementation on field activity, performance, muscle damage and redox responses following speed-endurance training in soccer players. METHODS: Ten well-trained, male soccer players completed three speed-endurance training trials, receiving whey protein (WP), soy protein (SP) or an isoenergetic placebo (PL; maltodextrin) according to a randomized, double-blind, crossover, repeated-measures design. A pre-loading period was applied in each trial during which protein supplementation was individually adjusted to reach a total protein intake of 1.5 g/kg/day, whereas in PL protein intake was adjusted at 0.8-1 g/kg/day. Following pre-loading, two speed-endurance training sessions (1 and 2) were performed 1 day apart, over a 3-day experimental period. During each session, field activity and heart rate were continuously monitored using global positioning system and heart rate monitors, respectively. Performance (isokinetic strength of knee extensors and flexors, maximal voluntary isometric contraction, speed, repeated sprint ability, countermovement jump), muscle damage (delayed-onset of muscle soreness, creatine kinase activity) and redox status (glutathione, total antioxidant capacity, protein carbonyls) were evaluated at baseline (pre), following pre-loading (post-load), and during recovery from speed-endurance training. RESULTS: High-intensity and high-speed running decreased (P ≤ 0.05) during speed-endurance training in all trials, but WP and SP mitigated this response. Isokinetic strength, maximal voluntary isometric contraction, 30-m speed, repeated sprint ability and countermovement jump performance were similarly deteriorated during recovery following speed-endurance training in all trials (P ≤ 0.05). 10 m speed was impaired at 24 h only in PL. Delayed-onset of muscle soreness, creatine kinase, total antioxidant capacity and protein carbonyls increased and glutathione decreased equally among trials following speed-endurance training (P ≤ 0.05), with SP inducing a faster recovery of protein carbonyls only at 48 h (P ≤ 0.05) compared to WP and PL. CONCLUSIONS: In conclusion, increasing daily protein intake to 1.5 g/kg through ingestion of either whey or soy protein supplements mitigates field performance deterioration during successive speed-endurance training sessions without affecting exercise-induced muscle damage and redox status markers. TRIAL REGISTRATION: Name of the registry: clinicaltrials.gov. TRIAL REGISTRATION: NCT03753321 . Date of registration: 12/10/2018.

Recovery Kinetics Following Small-Sided Games in Competitive Soccer Players: Does Player Density Size Matter?

PURPOSE: To examine the recovery kinetics of exercise-induced muscle damage (EIMD), neuromuscular fatigue, and performance following small-sided games (SSGs) of different densities in soccer. METHODS: Ten male players randomly completed 3 trials: a control trial (no SSGs), 4v4 SSGs (62.5 m2/player), and 8v8 SSGs (284.4 m2/player). External and internal load were monitored using GPS technology, heart-rate monitors, and rating of perceived exertion. Delayed-onset muscle soreness (DOMS), creatine kinase (CK), isokinetic strength, countermovement jump (CMJ), and sprint were determined at baseline, as well as at 24, 48, and 72 hours post-SSGs. Neuromuscular fatigue was assessed at baseline and at 1, 2, and 3 hours post-SSGs. RESULTS: DOMS increased (P < .05) in 4v4 for 72 hours and in 8v8 for 24 hours with that of knee flexors being more pronounced than that of extensors. CK increased (P < .05) in 4v4 for 72 hours and in 8v8 for 24 hours. Neuromuscular fatigue increased (P < .05) in 4v4 for 2 hours and in 8v8 for 3 hours. Strength declined (P < .05) in 4v4 for 48 hours and in 8v8 for 72 hours. CMJ decreased (P < .05) in 4v4 for 24 hours and in 8v8 for 48 hours. Sprint decreased (P < .05) for 48 hours in 4v4 and for 72 hours in 8v8. CONCLUSIONS: SSGs are associated with a prolonged rise of EIMD and induce short-term neuromuscular fatigue and slow recovery kinetics of strength, jump, and sprinting performance. The time for complete recovery is longer for SSGs of lower density.

Recovery Kinetics After Speed-Endurance Training in Male Soccer Players.

PURPOSE: To determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. METHODS: Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72 h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3 h posttraining. RESULTS: Fatigue increased (P < .05) in SEPT/1:5 (∼4-30%) for 3 h and in SEPT/1:8 (∼8-17%) for 2 h. Strength performance declined (P < .05) in both SEPT trials (∼5-20%) for 48 h. Speed decreased (∼4-18%; P < .05) for 72 h in SEPT/1:5 and for 48 h in SEPT/1:8. Countermovement-jump performance decreased (∼7-12%; P < .05) in both SEPT trials for 24 h. DOMS increased (P < .05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48 h. Creatine kinase increased (∼1- to 2-fold, P < .05) in both SEPT trials for 72 h. CONCLUSIONS: SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48 h), speed (72 h), and jump performance (24 h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics.

Exercise and Redox Status Responses Following Alpha-Lipoic Acid Supplementation in G6PD Deficient Individuals.

G6PD deficiency renders cells more susceptible to oxidative insults, while antioxidant dietary supplementation could restore redox balance and ameliorate exercise-induced oxidative stress. To examine the effects of alpha-lipoic acid (ALA) supplementation on redox status indices in G6PD deficient individuals, eight male adults with G6PD deficiency (D) participated in this randomized double-blind placebo-controlled crossover trial. Participants were randomly assigned to receive ALA (600 mg/day) or placebo for 4 weeks separated by a 4-week washout period. Before and at the end of each treatment period, participants exercised following an exhaustive treadmill exercise protocol. Blood samples were obtained before (at rest), immediately after and 1h after exercise for later analysis of total antioxidant capacity (TAC), uric acid, bilirubin, thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PC). ALA resulted in significantly increased resting TAC and bilirubin concentrations. Moreover, TAC increased immediately and 1h after exercise following both treatment periods, whereas bilirubin increased immediately after and 1h after exercise following only ALA. No significant change in uric acid, TBARS or PC was observed at any time point. ALA supplementation for 4 weeks may enhance antioxidant status in G6PD individuals; however, it does not affect redox responses to acute exercise until exhaustion or exercise performance.

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

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