Sprint Exercise Research Articles

Is training‐induced increase in muscle mass influenced by ACTN3 genotype?

INTRODUCTIONAlpha‐actinin‐3 is a skeletal muscle specific protein. A polymorphism in the ACTN3 gene (R577X) results in lack of alpha‐actinin‐3 protein in skeletal muscle of individuals with XX‐genotype. In sprint/power oriented elite athletes the prevalence of the X‐allele is much lower than in control populations, implying that lack of alpha‐actinin‐3 is detrimental for these athletes. The mechanistic link, however, is not fully established. Actn3 knock‐out mice are shown to have lower muscle mass. We have previously reported that humans with XX‐genotype have lower activation of mTOR‐signaling pathway in response to acute sprint exercise. This may indicate that the XX‐genotype is associated with an attenuated skeletal muscle hypertrophy in response to exercise. The aim of the present study was to examine the impact of ACTN3 genotype on hypertrophy signaling in skeletal muscle and on training‐induced increase in muscle mass.METHODS69 male and female subjects participating in five different longitudinal training studies with different training conditions were investigated. 20 subjects performed 5 weeks of supervised progressive knee‐extensor resistance training (study 1), 16 subjects performed 8 weeks of the same resistance training but with intervention by oral intake of acetylic acid (study 2) and 19 subjects performed 10 weeks of combined leg‐press and knee‐extensor resistance training with one leg (study 3a) followed by a detraining period and a new 5 weeks of the same resistance training but with both legs (pre‐trained leg (study 3b) and previously untrained leg (study 3c)). The volume of m. quadriceps, before and after the training periods, was assessed by MRI (study 1 and 2) or ultrasonography (study 3a, 3b and 3c). Muscle samples obtained in connection with an acute exercise bout in each study were analyzed for phosphorylation of p70S6k by western blot. DNA was extracted from muscle samples and genotyping for the R577X polymorphism was performed by allelic discrimination.RESULTSThe mean relative increase in muscle volume with training was (mean ±SD) 9.7 ±6 % and there was no significant difference between the studies. Therefore the impact of ACTN3 genotype on the training‐induced increase in muscle mass was analyzed in pooled data from all five studies. The relative increase in muscle volume in the different ACTN3 genotypes was (mean ±SD) 10.5 ±6 % in RR, 9.4 ±5 % in RX and 8.4 ±6 % in XX. The acute‐exercise induced increase in relative phosphorylation of p70S6k was (mean ±SD) 25 ±36 % in RR, 14 ±25 % in RX and 10 ±7% in XX. The observed differences between ACTN3‐genotypes were found to be not statistically significant.CONCLUSIONDespite the fact, that the relative increase in muscle volume and phosphorylation of p70S6k was numerically lower in the XX‐genotype as compared to RR and RX, there were no statistically significant differences between the genotypes. Our hypothesis, that ACTN3 genotype is a genetic modifier important for regulation of muscle mass, could thus not be confirmed by a present investigation. A type 2 error cannot be excluded, however, due to, the in general, low relative increase in muscle volume by this type of intervention.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Skeletal Muscle Pyruvate Dehydrogenase Phosphorylation and Lactate Accumulation During Sprint Exercise in Normoxia and Severe Acute Hypoxia: Effects of Antioxidants.

Compared to normoxia, during sprint exercise in severe acute hypoxia the glycolytic rate is increased leading to greater lactate accumulation, acidification, and oxidative stress. To determine the role played by pyruvate dehydrogenase (PDH) activation and reactive nitrogen and oxygen species (RNOS) in muscle lactate accumulation, nine volunteers performed a single 30-s sprint (Wingate test) on four occasions: two after the ingestion of placebo and another two following the intake of antioxidants, while breathing either hypoxic gas (PIO2 = 75 mmHg) or room air (PIO2 = 143 mmHg). Vastus lateralis muscle biopsies were obtained before, immediately after, 30 and 120 min post-sprint. Antioxidants reduced the glycolytic rate without altering performance or VO2. Immediately after the sprints, Ser293- and Ser300-PDH-E1α phosphorylations were reduced to similar levels in all conditions (~66 and 91%, respectively). However, 30 min into recovery Ser293-PDH-E1α phosphorylation reached pre-exercise values while Ser300-PDH-E1α was still reduced by 44%. Thirty minutes after the sprint Ser293-PDH-E1α phosphorylation was greater with antioxidants, resulting in 74% higher muscle lactate concentration. Changes in Ser293 and Ser300-PDH-E1α phosphorylation from pre to immediately after the sprints were linearly related after placebo (r = 0.74, P < 0.001; n = 18), but not after antioxidants ingestion (r = 0.35, P = 0.15). In summary, lactate accumulation during sprint exercise in severe acute hypoxia is not caused by a reduced activation of the PDH. The ingestion of antioxidants is associated with increased PDH re-phosphorylation and slower elimination of muscle lactate during the recovery period. Ser293 re-phosphorylates at a faster rate than Ser300-PDH-E1α during the recovery period, suggesting slightly different regulatory mechanisms.

The effects of taurine on repeat sprint cycling after low or high cadence exhaustive exercise in females

This study investigated the effects of taurine on repeated sprint exercise, performed after fixed incremental ramp exercise to exhaustion at isokinetic high (90r/min) or low (50r/min) cadences. In a double-blind, repeated measures design, nine females completed an incremental ramp test to volitional exhaustion, followed by 2min active recovery and 6×10s sprints on a cycle ergometer, in one of four conditions: high cadence (90r/min) + taurine (50mg/kg body mass); high cadence + placebo (3mg/kg body mass maltodextrin); low cadence (50r/min) + taurine; low cadence + placebo. Heart rate (HR) and blood lactate concentration B[La] were measured before and after the ramp test and after the sprints. Taurine lowered HR vs. placebo prior to the ramp test (P = 0.004; d = 2.1). There was an effect of condition on ramp performance (P < 0.001), with higher end-test power (d = 3.7) in taurine conditions. During repeated sprints, there was a condition×time interaction (P = 0.002), with higher peak sprint power in the placebo conditions compared to taurine (sprint 2-6; P < 0.05). B[La] was higher in taurine compared to placebo post-ramp (P = 0.004; d = 4.7). Taurine-lowered pre-exercise HR and improved incremental end-test power output, with subsequent detrimental effects on sprint performance, independent of cadence. Short endurance performance can be acutely enhanced after taurine ingestion but this effect might not be maintained across longer periods of exercise or induce the need for longer recovery periods.

The effect of lower limb occlusion on recovery following sprint exercise in academy rugby players

ObjectivesThe effects of vascular occlusion on recovery of physiological and neuromuscular markers over 24h, and hormonal reactivity to subsequent exercise were investigated. DesignCounterbalanced, randomised, crossover. MethodsAcademy rugby players (n=24) completed six 50-m sprints (5-min inter-set recovery) before occlusion cuff application (thighs) and intermittent inflation to 171–266mmHg (Recovery) or 15mmHg (Con) for 12-min (two sets, 3-min repetitions, 3-min non-occluded reperfusion). Countermovement jumps, blood (lactate, creatine kinase), saliva (testosterone, cortisol), and perceptual (soreness, recovery) responses were measured before (baseline) and after (post, +2h, +24h) sprinting. Saliva was sampled after a 30-min resistance exercise session performed 24h after sprinting. ResultsAlthough sprinting (total: 40.0±2.8s, p=0.238; average: 6.7±0.5s, p=0.674) influenced creatine kinase (p<0.001, +457.1±327.3μL−1, at 24h), lactate (p<0.001, 6.8±2.3mmolL−1, post), testosterone (p<0.001, −55.9±63.2pgmL−1, at 2h) and cortisol (p<0.001, −0.3±0.3μgdL−1, at 2h) concentrations, countermovement jump power output (p<0.001, −409.6±310.1W; −5.4±3.4cm, post), perceived recovery (p<0.001, −3.0±2.3, post), and muscle soreness (p<0.001; 1.5±1.1, at 24h), vascular occlusion had no effect (all p>0.05) on recovery. In response to subsequent exercise performed 24h after vascular occlusion, testosterone increased pre-to-post-exercise (Recovery: p=0.031, 21.6±44.9pgmL−1; Con: p=0.178, 10.6±36.6pgmL−1) however Δtestosterone was not significantly different (p=0.109) between conditions. ConclusionsVascular occlusion had no effect on physiological or neuromuscular markers 2h or 24h after sprinting or in response to a physical stress test.

Effects of Resisted Sprint Training and Traditional Power Training on Sprint, Jump, and Balance Performance in Healthy Young Adults: A Randomized Controlled Trial.

Power training programs have proved to be effective in improving components of physical fitness such as speed. According to the concept of training specificity, it was postulated that exercises must attempt to closely mimic the demands of the respective activity. When transferring this idea to speed development, the purpose of the present study was to examine the effects of resisted sprint (RST) vs. traditional power training (TPT) on physical fitness in healthy young adults. Thirty-five healthy, physically active adults were randomly assigned to a RST (n = 10, 23 ± 3 years), a TPT (n = 9, 23 ± 3 years), or a passive control group (n = 16, 23 ± 2 years). RST and TPT exercised for 6 weeks with three training sessions/week each lasting 45–60 min. RST comprised frontal and lateral sprint exercises using an expander system with increasing levels of resistance that was attached to a treadmill (h/p/cosmos). TPT included ballistic strength training at 40% of the one-repetition-maximum for the lower limbs (e.g., leg press, knee extensions). Before and after training, sprint (20-m sprint), change-of-direction speed (T-agility test), jump (drop, countermovement jump), and balance performances (Y balance test) were assessed. ANCOVA statistics revealed large main effects of group for 20-m sprint velocity and ground contact time (0.81 ≤ d ≤ 1.00). Post-hoc tests showed higher sprint velocity following RST and TPT (0.69 ≤ d ≤ 0.82) when compared to the control group, but no difference between RST and TPT. Pre-to-post changes amounted to 4.5% for RST [90%CI: (−1.1%;10.1%), d = 1.23] and 2.6% for TPT [90%CI: (0.4%;4.8%), d = 1.59]. Additionally, ground contact times during sprinting were shorter following RST and TPT (0.68 ≤ d ≤ 1.09) compared to the control group, but no difference between RST and TPT. Pre-to-post changes amounted to −6.3% for RST [90%CI: (−11.4%;−1.1%), d = 1.45) and −2.7% for TPT [90%CI: (−4.2%;−1.2%), d = 2.36]. Finally, effects for change-of-direction speed, jump, and balance performance varied from small-to-large. The present findings indicate that 6 weeks of RST and TPT produced similar effects on 20-m sprint performance compared with a passive control in healthy and physically active, young adults. However, no training-related effects were found for change-of-direction speed, jump and balance performance. We conclude that both training regimes can be applied for speed development.

Self-confidence and affect responses to short-term sprint interval training

The study aimed to investigate the effects of repeated sprint (RS) training on somatic anxiety (SA), cognitive anxiety (CA), self-confidence (SC), rating of perceived exertion (RPE) and repeated sprint ability (RSA) indicators in elite young soccer players.Thirty elite soccer players in the first football league (age: 17.8±0.9years) volunteered to participate in this study. They were randomly assigned to one of two groups: a repeated sprint training group (RST-G; n=15) and a control group (CON-G; n=15). RST-G participated in 6weeks of intensive training based on RS (6×(20+20m) runs, with 20s passive recovery interval between sprints, 3 times/week). Before and after the 6-week intervention, all participants performed a RSA test and completed a Competitive Scale Anxiety Inventory (CSAI-2) and the RPE. After training RST-G showed a very significant (p<0.000) increase in RSA total time performance relative to controls. Despite the faster sprint pace, the RPE also decreased significantly (p<0.005) in RST-G, and their self confidence was significantly greater (p<0.01), while the cognitive (p<0.01) and somatic (p<0.000) components of their anxiety state decreased. When practiced regularly, short bouts of sprint exercises improve anaerobic performance associated with a reduction in anxiety state and an increase in SC which may probably boost competitive performance.

Physiological parameter values in greyhounds before and after high-intensity exercise.

Dog sports competitions have greatly expanded. The availability of reference values for each type of activity could help assess fitness accurately. Heart rate (HR), blood lactate (BL) and rectal temperature (RT) are relevant physiological parameters to determine the dogs response to effort. Previous studies in greyhounds have reported the effect of high-intensity exercise on many physiological parameters immediately after completing different racing distances and recovery times. However, there are no studies concerning physiological changes over shorter racing distances. We therefore assessed the effect of sprint exercise on HR, BL and RT in nine greyhounds performing sprint exercise over a 100-m distance chasing a lure. After the exercise, dogs underwent a passive 10-min recovery phase. Before the exercise, immediately after it and at 5 and 10 min during recovery, HR and RT were assessed and blood samples were collected for BL determination. HR, BL and RT values increased significantly after the exercise (P<0.01). Whereas HR returned to pre-exercise values at 10 min during the recovery phase (P>0.1), BL concentration and RT remained increased (P<0.01). The abrupt increase in HR, BL and RT values observed immediately after the exercise indicates the high intensity of the effort performed. Similarly, BL concentration after the exercise exceeded the 4 mmol/L lactate threshold, suggesting a predominant anaerobic metabolism during effort. Although HR returned to pre-exercise values 10 min after the exercise, a more extensive recovery phase would be necessary for a total return to resting values, particularly for BL and RT. In greyhounds subjected to high-intensity exercise, HR, BL and RT were reliable physiological parameters to accurately assess the physiological response to effort. The use of sprint exercises over short racing distances could be useful for appropriately monitoring fitness in sporting dogs.

Effects of preconditioning hamstring resistance exercises on repeated sprinting-induced muscle damage in female soccer players.

To examine whether adding preconditioning hamstring resistance exercises to a regular warm-up prior to a repeated sprinting exercise provides protection against the sprinting-induced muscle damage. Ten female soccer players (mean ± SD age: 21.3 ± 4.5yrs; height: 171.34 ± 8.29 cm; weight: 68.53 ± 11.27 kg) participated in this study. After the familiarization visit, the subjects completed three separate randomly sequenced experimental visits, during which three different warm-up interventions were performed before the muscle-damaging protocol (12 sets of 30-m maximal repeated sprints): 1. Regular running and static stretching (Control); 2. Control with hyperextensions (HE); 3. Control with single leg Romanian deadlift (SLRD). Before (Pre), immediately (Post0), 24 hours (24hr), and 48 hours after (48hr) the sprints, hamstring muscle thickness, muscle stiffness, knee flexion eccentric peak torque, knee extension concentric peak torque, and functional hamstring to quadriceps ratios were measured. Repeated sprints have induced muscle damage (e.g., an average of 42% knee flexion eccentric strength reduction) in all three conditions. After the SLRD, hamstring muscle thickness decreased from 24hr to 48hr (p < 0.001). Additionally, muscle stiffness and eccentric strength for the SLRD showed no difference from baseline at 24hr and 48hr, respectively. When compared with the SLRD at 48hr, the muscle stiffness and the eccentric strength were greater and lower, respectively, in other protocols. The SLRD protocol had protective effect on sprinting-induced muscle damage markers than other protocols. Athletes whose competitions/training are densely scheduled may take advantage of this strategy to facilitate muscle recovery.

Virtual reality as a countermeasure for physical training in bed rest and artificial gravity conditions.

Virtual reality as a countermeasure for physical training in bed rest and artificial gravity conditions.

Ischemic Preconditioning Does Not Alter Performance in Multidirectional High-Intensity Intermittent Exercise.

Purpose: Research dealing with ischemic preconditioning (IPC) has primarily focused on variables associated to endurance performance with little research about the acute responses of IPC on repeated multidirectional running sprint performance. Here we aimed to investigate the effects of IPC of the arms and the legs on repeated running sprint performance with changes-of-direction (COD) movements.Methods: Thirteen moderately-to-well-trained team-sport athletes (7 males; 6 females; age: 24 ± 2 years, size: 175 ± 8 cm, body mass: 67.9 ± 8.1 kg) performed 16 × 30 m all-out sprints (15 s rest) with multidirectional COD movements on a Speedcourt with IPC (3 × 5 min) of the legs (IPCleg; 240 mm Hg) or of the arms (remote IPC: IPCremote; 180–190 mm Hg) 45 min before the sprints and a control trial (CON; 20 mm Hg).Results: The mean (±SD) time for the 16 × 30 m multidirectional COD sprints was similar between IPCleg (Mean t: 16.0 ± 1.8 s), IPCremote (16.2 ± 1.7 s), and CON (16.0 ± 1.6 s; p = 0.50). No statistical differences in oxygen uptake (mean difference: 0%), heart rate (1.1%) nor muscle oxygen saturation of the vastus lateralis (4.7%) and biceps brachii (7.8%) between the three conditions were evident (all p > 0.05).Conclusions: IPC (3 × 5 min) of the legs (220 mm Hg) or arms (180–190 mm Hg; remote IPC) applied 45 min before 16 × 30 m repeated multidirectional running sprint exercise does not improve sprint performance, oxygen uptake, heart rate nor muscle oxygen saturation of the vastus lateralis muscle when compared to a control trial.

Recovery benefits of using a heat and moisture exchange mask during sprint exercise in cold temperatures.

Objectives:Breathing cold air can lead to bronchoconstriction and peripheral vasoconstriction, both of which could impact muscular performance by affecting metabolic demands during exercise. Successful solutions dealing with these physiological changes during exercise in the cold has been lacking; therefore, we investigated the influence of a heat and moisture exchange mask during exercise in the cold.Methods:There were three trial arms within this study: wearing the heat and moisture exchange mask during the rest periods in the cold, no-mask application during the rest periods in the cold, and a trial at room temperature (22°C). Eight subjects cycled in four 35 kJ sprint sessions with each session separated by 20 min rest period. Workload was 4% of body mass.Results:Mean sprint times were faster with heat and moisture exchange mask and room temperature trial than cold, no-mask trial (133.8 ± 8.6, 134.9 ± 8.8, and 138.0 ± 8.4 s (p = 0.001)). Systolic blood pressure and mean arterial pressure were greater during the cold trial with no mask (15% and 13%, respectively), and heart rate was 10 bpm less during the third rest or recovery period during cold, no mask compared to the heat and moisture exchange mask and room temperature trials. Subjects demonstrated significant decreases in vital capacity and peak expiratory flow rate during the cold with no mask applied during the rest periods.Conclusions:These negative responses to cold exposure were alleviated by the use of a heat and moisture exchange mask worn during the rest intervals by minimizing cold-induced temperature stress on the respiratory system with subsequent maintenance of cardiovascular function.

Impact of inserted long rest periods during repeated sprint exercise on performance adaptation

Repeated sprint training consists of a series of brief maximal sprints, 3–7 s in duration, separated by short rest periods of <60 s. However, little is known about the influence of different rest period lengths between sprints on performance adaptation. We determined the influence of inserting long rest periods during repeated sprint training on performance adaptation in competitive athletes. Twenty-one well-trained athletes were separated into either the short rest period group (SHORT; n = 10) or the long rest period group (LONG; n = 11). The training protocol for both groups consisted of two sets of 12 × 6-s maximal cycle sprints with 24 s of rest between sprints. However, in the LONG group, an active rest period of 7 min was inserted every three sprints to attenuate the power output decrement during the latter half of the sprints. The training was performed 3 d/week for 3 weeks. Before and after the training period, repeated sprint ability [12 × 6-s maximal sprint (pedaling) with 24-s rest] was evaluated. Maximal power output during the repeated sprint test was significantly increased only in the LONG group (P < .05). Both groups showed a similar increase in power output during the latter half of sprints (P < .05). The LONG group showed a significant increase in (P < .05). These results suggest that repeated sprint training with insertion of longer rest periods is an efficient strategy for improving maximal power output compared with the same training separated by short rest periods alone.

Responses of low and high compression during recovery after repeated sprint training in well-trained handball players

The aim of the study was to investigate the effects of wearing various levels of compression following repeated and exhausting sprint exercise on variables related to recovery. Twelve well-trained handball players performed three sessions of repeated and exhausting sprint exercise (30 × 30m). Directly after each session the participants wore tights extending from below the hip to the foot with either 0, 10, or 25 mm Hg of compression onto the thigh and calf muscles. 48 h after the training session all participants performed 5 × 30m sprints and counter movement jumps. Before, directly after, 24 h, and 48 h after the training session venous blood samples were drawn for the determination of creatine kinase (CK), urea, C-reactive protein (CRP). At the same time points, subjective ratings of the Acute Recovery and Stress Scale (ARSS) questionnaires were obtained. The results for plasma concentrations of CK and urea showed ‘likely’ to ‘very, very likely’ beneficial effects for compression garments exerting 10 mm Hg of compression (p = 0.06–1.0). With regard to sprint and jump performance no differences were evident between 0, 10, and 25 mm Hg (p = 0.07–1.0). In addition, subjective scores from the ARSS did not differ between conditions over time (p > 0.05). We conclude that the application of 10 mm Hg leg compression compared to 0 and 25 mm Hg of compression during 48 h of recovery from repeated and exhausting sprints lowered the plasma concentrations of CK and urea with no improvements in recovery for performance.

Postexercise serum hepcidin response to repeated sprint exercise under normoxic and hypoxic conditions.

We determined the effects of repeated sprint exercise under normoxic and hypoxic conditions on serum hepcidin levels. Ten male athletes (age: 20.9 ± 0.3 years; height: 175.7 ± 6.0 cm; weight: 67.3 ± 6.3 kg) performed 2 exercise trials under normoxic (NOR; fraction of inspiratory oxygen (FiO2): 20.9%) or hypoxic conditions (HYPO; FiO2: 14.5%). The exercise consisted of 3 sets of 5 × 6 s of maximal pedaling (30-s rest periods between sprints, 10-min rest periods between sets). Blood samples were collected before exercise, immediately after exercise, and 1 and 3 h after exercise. Serum hepcidin levels were significantly elevated after exercise in both trials (both P < 0.01), with no significant difference between the trials. The postexercise blood lactate levels were significantly higher in the HYPO than the NOR (P < 0.05). Both trials caused similar increases in plasma interleukin-6 and serum iron levels (P < 0.001), with no significant difference between the trials. A significant interaction (trial × time) was apparent in terms of serum erythropoietin (EPO) levels (P = 0.003). The EPO level was significantly higher in the HYPO than the NOR at 3 h after exercise (P < 0.05). In conclusion, repeated sprint exercise significantly increased serum hepcidin levels to similar extent in 2 trials, despite differences in the inspired oxygen concentrations during both the exercise and the 3-h postexercise period.

Effect of High-Speed Strength Training on Physical Performance in Young Soccer Players of Different Ages.

Rodríguez-Rosell, D, Franco-Márquez, F, Mora-Custodio, R, and González-Badillo, JJ. Effect of high-speed strength training on physical performance in young soccer players of different ages. J Strength Cond Res 31(9): 2498-2508, 2017-The aim of the present study was to compare the effectiveness of low-load, low-volume weight training combined with plyometrics on strength, sprint, and jump performance in soccer players of different ages. Eighty-six soccer players from the same academy were categorized into 3 groups by age (under 13 years, U13, n = 30; under 15, U15, n = 28; and under 17, U17, n = 28) and then randomly assigned into 2 subgroups: a strength training group (STG) and a control group (CG). The strength training program was performed twice a week for 6 weeks and consisted of full squats (load: 45-60% 1 repetition maximum; volume: 3 set of 8-4 repetitions), jumps, and straight line sprint exercises. After training intervention, the STGs showed significant improvements in maximal strength (7.5-54.5%; p < 0.001), jump height (5.7-12.5%; p <0.01-0.001), and sprint time (-3.7 to -1.2%; p ≤0.05-0.001), whereas no significant gains were found for any variable in the CGs. Comparison between experimental groups resulted in a greater magnitude of change for U13 compared with U15 (effect sizes [ES]: 0.10-0.53) and U17 (ES: 0.14-1.41) soccer players in most variables, whereas U15 showed higher improvements in jump and strength parameters than U17 (ES: 0.25-0.90) soccer players. Thus, although our results indicates that a combined weight training and plyometrics program may be effective in eliciting gains in strength, jump, and sprint in soccer players of different ages, the training program used appears to be generally less effective as the age of the soccer players increased. Therefore, it appears that training characteristics (mainly volume, intensity, and type of exercise) should be modified in relation to maturity status and initial strength level.

Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise.

Nutrient ingestion is known to increase the exercise-induced stimulation of muscle protein synthesis following resistance exercise. Less is known about the effect of nutrients on muscle protein synthesis following sprint exercise. At two occasions separated by 1 mo, 12 healthy subjects performed three 30-s sprints with 20-min rest between bouts. In randomized order, they consumed a drink with essential amino acids and maltodextrin (nutrient) or flavored water (placebo). Muscle biopsies were obtained 80 and 200 min after the last sprint, and blood samples were taken repeatedly during the experiment. Fractional synthetic rate (FSR) was measured by continuous infusion of l-[2H5]phenylalanine up to 200 min postexercise. The mRNA expression and protein expression of SNAT2 were both 1.4-fold higher ( P < 0.05) after nutrient intake compared with placebo at 200 min postexercise. Phosphorylated Akt, mammalian target of rapamycin (mTOR), and p70S6k were 1.7- to 3.6-fold higher ( P < 0.01) 80 min after the last sprint with nutrient ingestion as compared with placebo. In addition, FSR was higher ( P < 0.05) with nutrients when plasma phenylalanine (FSRplasma) was used as a precursor but not when intracellular phenylalanine (FSRmuscle) was used. Significant correlations were also found between FSRplasma on the one hand and plasma leucine and serum insulin on the other hand in the nutrient condition. The results show that nutrient ingestion induces the expression of the amino acid transporter SNAT2 stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis following sprint exercise. NEW & NOTEWORTHY There is limited knowledge regarding the effect of nutrients on muscle protein synthesis following sprint as compared with resistance exercise. The results demonstrate that nutrient ingestion during repeated 30-s bouts of sprint exercise induces expression of the amino acid transporter SNAT2 and stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis. Future studies to explore the chronic effects of nutritional ingestion during sprint exercise sessions on muscle mass accretion are warranted.

Skeletal muscle signaling, metabolism, and performance during sprint exercise in severe acute hypoxia after the ingestion of antioxidants.

The aim of this study was to determine if reactive oxygen species (ROS) could play a role in blunting Thr172-AMP-activated protein kinase (AMPK)-α phosphorylation in human skeletal muscle after sprint exercise in hypoxia and to elucidate the potential signaling mechanisms responsible for this response. Nine volunteers performed a single 30-s sprint (Wingate test) in two occasions while breathing hypoxic gas ([Formula: see text] = 75 mmHg): one after the ingestion of placebo and another following the intake of antioxidants (α-lipoic acid, vitamin C, and vitamin E), with a randomized double-blind design. Vastus lateralis muscle biopsies were obtained before, immediately after, and 30- and 120-min postsprint. Compared with the control condition, the ingestion of antioxidants resulted in lower plasma carbonylated proteins, attenuated elevation of the AMP-to-ATP molar ratio, and reduced glycolytic rate (P < 0.05) without significant effects on performance or V̇o2 The ingestion of antioxidants did not alter the basal muscle signaling. Thr172-AMPKα and Thr184/187-transforming growth factor-β-activated kinase 1 (TAK1) phosphorylation were not increased after the sprint regardless of the ingestion of antioxidants. Thr286-CaMKII phosphorylation was increased after the sprint, but this response was blunted by the antioxidants. Ser485-AMPKα1/Ser491-AMPKα2 phosphorylation increased immediately after the sprints coincident with increased Akt phosphorylation. In summary, antioxidants attenuate the glycolytic response to sprint exercise in severe acute hypoxia and modify the muscle signaling response to exercise. Ser485-AMPKα1/Ser491-AMPKα2 phosphorylation, a known mechanism of Thr172-AMPKα phosphorylation inhibition, is increased immediately after sprint exercise in hypoxia, probably by a mechanism independent of ROS.NEW & NOTEWORTHY The glycolytic rate is increased during sprint exercise in severe acute hypoxia. This study showed that the ingestion of antioxidants before sprint exercise in severe acute hypoxia reduced the glycolytic rate and attenuated the increases of the AMP-to-ATP and the reduction of the NAD+-to-NADH.H+ ratios. This resulted in a modified muscle signaling response with a blunted Thr286-CaMKII but similar AMP-activated protein kinase phosphorylation responses in the sprints preceded by the ingestion of antioxidants.

A COMPARISON OF THE EFFECTS OF GENDER, ACTIVE RECOVERY AND COLD BATH METHODS ON LACTIC ACID LEVELS

This study aims to determine: (1) The difference effect of active recovery and cold bath to lactic acid levels. (2) The difference of lactic acid levels between men and women. (3) The effect of the interaction between recovery method (active recovery and cold bath) and gender of the lactic acid levels after the maximum exercise. The research is using experimental methods research factorial design 2 x 2. The exercise maximum award is 400 m sprint. The population in this study is composed by a number of 32 volleyball athletes, consisting of 16 male and 16 female athletes. Groups of men and women were divided into two groups, each group consisting of 8 people. Each member of the group will be given exercises with maximum intensity of 400 m. After sprint exercise maximum intensity samples were then measured, the levels of lactic acid in the blood (pretest). Next, do recovery method that is active recovery for 20 minutes and the cold bath for 20 minutes with a temperature of 15 0 C- 10 0 C in the group of men and women. After 20 minutes, the samples are re-measured for the blood lactic acid levels (posttest). The analysis technique of the data in this study is Two Way Analysis of Variance (ANOVA Two-Way). The results showed that: (1) There is a significant difference between the active recovery and cold bath of lactic acid levels, which gained F (o) at 45.96 and the value of p = .00 (P .05). (1) There are differences between the effects of active recovery method and a cold bath to the reduction in blood lactic acid levels. The effect of cold bath method is better than the active recovery method in lowering levels of blood lactic acid. (2) There are differences in blood lactic acid levels between men and women. The reduction in lactic acid levels in men is faster than women. (3) There is no interaction effect between recovery methods and sex against lactic acid levels. Both groups of men and women have a reduction in blood lactic acid levels that are higher with cold bath recovery methods. Article visualizations:

CRY1/2 Selectively Repress PPARδ and Limit Exercise Capacity

Cellular metabolite balance and mitochondrial function are under circadian control, but the pathways connecting the molecular clock to these functions are unclear. Peroxisome proliferator-activated receptor delta (PPARδ) enables preferential utilizationof lipids as fuel during exercise and is a major driver of exercise endurance. We show here that the circadian repressors CRY1 and CRY2 function as co-repressors for PPARδ. Cry1-/-;Cry2-/- myotubes and muscles exhibit elevated expression of PPARδ target genes, particularly in the context of exercise. Notably, CRY1/2 seem to repress a distinct subset of PPARδ target genes in muscle compared to the co-repressor NCOR1. Invivo, genetic disruption of Cry1 and Cry2 enhances sprint exercise performance in mice. Collectively, our data demonstrate that CRY1 and CRY2 modulate exercise physiology by altering the activity of several transcription factors, including CLOCK/BMAL1 and PPARδ, and thereby alter energy storage and substrate selection for energy production.

The Effect of Exercise Training Type on Paraoxonase-1 and Lipid Profile in Rats

Background: Paraoxonase-1 (PON1) is an anti-atherosclerotic enzyme that protects high-density lipoprotein (HDL) and low-density lipoprotein (LDL) against oxidation. There are contradictory studies about the effects of exercise training on PON1 activity. Objectives: The purpose of the present study was to elucidate the effects of sprint and endurance exercise training on serum PON1 activity and lipid profile in rats. Methods: Twenty-four Albino Wistar rats were divided to sedentary control (SC), endurance training (ET), and sprint training (ST) groups. The animals were subjected to endurance (at a speed of 27 m/minute) and sprint (at a speed of 40 to 54 m/minute) training on a treadmill for 6 weeks, 6 days per week. Using commercial kits, PON1 activity and lipid profile levels were measured by spectrophotometry and enzymatic methods, respectively. The data were analyzed by one-way analysis of variance followed by Tukey’s post-hoc test at P < 0.05 level. Results: Both ET and ST regimens increased PON1 activity in the serum, and the alteration was greater following ST than ET (F1, 23 = 17.87, P = 0.001). In contrast, neither ST nor ET changed significantly the serum levels of triglyceride (F1, 23 = 0.288, P = 0.753), total cholesterol (F1, 23 = 0.385, P = 0.685), LDL (F1, 23 = 1.07, P = 0.361), and HDL (F1, 23 = 1.36, P = 0.277). In addition, serum PON1 activity was positively correlated with serum HDL levels in rats (R = 0.44, P = 0.032). Conclusions: Despite the lack of change in serum lipid profile, sprint training can lead to greater protection against lipid peroxidation than endurance training through increases in serum PON1 activity. Keywords: Sprint Training, Endurance Training, Paraoxonase 1, Lipid Profile