Effects of 7-day polyphenol powder supplementation on cycling performance and lung function in an ozone-polluted environment.

PURPOSE: Polluted environments can adversely affect lung function and exercise performance. Evidence suggests that some nutrient supplements may offset pollution's detrimental effects. This study examined the effect of polyphenol supplementation on lung function and exercise performance in an ozone-polluted environment. METHODS: Ten male cyclists (mean ± SD: age, 43.8 ± 12.4 years; height, 177.8 ± 7.1 cm; weight, 76.03 ± 7.88 kg; VO2max 4.12 ± 0.72 L min-1) initially completed a baseline maximal incremental test and maximal effort 4 km time trial in ambient air. Thereafter cyclists completed two trials in an ozone-polluted environment (0.25 ppm) following seven days of supplementation with either polyphenol (PB) or placebo (PL). Experimental trials consisted of a three-stage submaximal test (50%, 60% and 70% incremental peak power) followed by a 4 km time trial. Lung function was measured pre- and post-exercise via spirometry and adverse respiratory symptoms with a Likert scale. RESULTS: Ozone exposure significantly reduced (p < 0.05) lung function relative to ambient air. There were no significant differences (p > 0.05) in measured variables across the three submaximal intensities. There was a small (d = 0.31) non-significant difference (p = 0.09) in 4 km performance in PB (406.43 ± 50.29 s) vs. PL (426.20 ± 75.06 s). Oxygen consumption during the time trial was greater in PB (3.49 ± 0.71 L min-1) vs PL (3.32 ± 0.71 L min-1, p = 0.01, d = 0.24). Cough severity (SOC) was lower (p = 0.03) with PB relative to PL. CONCLUSION: PB supplementation may provide small benefits to performance and reduce cough symptoms during high-intensity exercise in ozone-polluted environments.

Is Stryd critical power a meaningful parameter for runners?

Stryd is a foot pod that reliably estimates running power. Our objectives were to examine the efficacy of the website-generated Stryd critical power (CPSTRYD) as a meaningful parameter for runners. 20 runners performed their regular training while wearing Stryd for a minimum of 6 weeks to generate CPSTRYD. Runners completed laboratory graded exercise testing, and outdoor 1500 m and 5000 m time trails. CPSTRYD was most similar to the second ventilatory threshold (VT2) or the onset of blood lactate accumulation (OBLA) and is highly predictive of running performance. Stryd ground contact time (GCT) was a predictor of performance when comparing runners at the same submaximal treadmill speed. CPSTRYD generated from outdoor running is equivalent to that calculated using an established CP model. However, variance between different methods of CP estimation must be a consideration for runners and coaches. Stryd offers meaningful data for runners including a realistic estimate of CP.

The Effects of Blackcurrant and Caffeine Combinations on Performance and Physiology During Repeated High-Intensity Cycling.

Blackcurrant juices and extracts containing anthocyanin may provide ergogenic benefits to sports performance. However, there are no studies examining the effects of coingestion of blackcurrant and caffeine. This investigation examined the effects of acute supplementation with a proprietary blackcurrant beverage administered in isolation or in combination with caffeine on repeated high-intensity cycling. Twelve well-trained male cyclists (mean ± SD: age, 39.5 ± 11.4 years; height, 177.9 ± 5.7 cm; weight, 78.2 ± 8.9 kg; and peak oxygen consumption, 4.71 ± 0.61 L/min) completed experimental sessions consisting of repeated (8 × 5 min) maximal intensity efforts. Four experimental treatments were administered in a double-blind, balanced Latin square design: blackcurrant + caffeine, blackcurrant + placebo, caffeine + placebo and placebo + placebo. Differences in power output, heart rate, oxygen consumption, muscle oxygen saturation, rate of perceived exertion, and cognitive function (Stroop) were compared between treatments using two-way repeated-measures analysis of variance and effect size analysis. There were no significant differences (p > .05) in either physiological or cognitive variables with any supplement treatment (blackcurrant + caffeine, blackcurrant + placebo, and caffeine + placebo) relative to placebo + placebo. Moreover, any observed differences were deemed trivial (d < 0.2) in magnitude. However, power output was lower (p < .05) in blackcurrant + placebo compared with blackcurrant + caffeine. A blackcurrant extract beverage administered in isolation or combination with caffeine provided no beneficial effect on cycling performance or physiological measures relative to a placebo control.

The effects of muscle blood flow restriction during running training on measures of aerobic capacity and run time to exhaustion.

PURPOSE: Training with blood flow restriction (BFR) is known to enhance muscle mass and strength during resistance training activities. However, little is known about the BFR effects during aerobic training. This investigation examines the effects of running training performed with or without BFR on physiology and performance. METHOD: Sixteen subjects (age 24.9 ± 6.9 years, height 172.9 ± 7.8 cm, weight 75.1 ± 13.8 kg) were assigned to a BFR or control (CON) group for eight sessions of training. Before and after training, subjects completed an incremental test to determine peak running velocity (PRV) maximal oxygen uptake ([Formula: see text]) and running economy (RE), followed by a time to exhaustion run (TTE) performed at PRV. Training for both groups consisted of progressively increasing volumes of 30-s repetitions completed at 80% of PRV. RESULTS: The BFR and CON groups reported gains (6.3 ± 3.5 vs 4.0 ± 3.3%) in [Formula: see text] following training with only trivial (ES = 0.18) differences between groups. Similarly, PRV and incremental test time increased in both training groups with a small (ES ~ 0.3) additional enhancement in favour of the BFR group. Running economy improved in the BFR group but not in CON (ES = 0.4). TTE also increased in both BFR (27 ± 9%) and CON groups (17 ± 6%) with a small (ES = 0.31) additional benefit in favour of the BFR group. CONCLUSIONS: Using BFR during training appears to confer small but potentially worthwhile improvements in RE, PRV and TTE measures. The improvements following BFR training are likely due to muscular rather than cardiovascular function.

Validity and Reliability of the PowerCal Device for Estimating Power Output During Cycling Time Trials.

Costa, VP, Guglielmo, LGA, and Paton, CD. Validity and reliability of the PowerCal device for estimating power output during cycling time trials. J Strength Cond Res 31(1): 227-232, 2017-This study assessed the validity and reproducibility of the PowerCal device for estimating power output (PO) during cycling hilly time trials (TTs). Twenty-one well-trained men cyclists performed an incremental exercise test and three 20-km TTs (34.1 ± 10.6 years; 73.2 ± 3.2 kg, 176.8 ± 6.2 cm; maximal PO, 334 ± 31 W; maximal oxygen uptake, 61.0 ± 4.2 ml·kg·min). The first TT was used for familiarization, and the tests were separated by at least 72 hours. Mean PO over the 20-km TT was significantly greater for the Velotron (282 ± 27 W) than for the PowerCal (242 ± 28 W). The mean power over each kilometer of the trial ranged from 5.8 to 23.4% greater on the Velotron than on the PowerCal. High within-subject variation between the trials was substantially greater for the PowerCal (4.9%) than for the Velotron (1.8%). High coefficients of variation scores for the Velotron test-retest were found to be concentrated in the beginning and final meters of the TT (∼6.0%), whereas the scores were lower in the middle of the trials (∼3.0%). In contrast, the PowerCal test-retest achieved a high coefficient of variation (∼6.0%) in each km over the TT. Thus, the PowerCal device should be used with caution during cycling activities because it is not reliable and underestimates PO.

Acute physiological responses of blood flow restriction between high-intensity interval repetitions in trained cyclists.

Blood flow restriction (BFR) is increasingly being used to enhance aerobic performance in endurance athletes. This study examined physiological responses to BFR applied in recovery phases within a high-intensity interval training (HIIT) session in trained cyclists. Eleven competitive road cyclists (mean ± SD, age: 28 ± 7 years, body mass: 69 ± 6 kg, peak oxygen uptake: 65 ± 9 mL · kg-1 · min-1) completed two randomised crossover conditions: HIIT with (BFR) and without (CON) BFR applied during recovery phases. HIIT consisted of six 30-s cycling bouts at an intensity equivalent to 85% of maximal 30-s power (523 ± 93 W), interspersed with 4.5-min recovery. BFR (200 mmHg, 12 cm cuff width) was applied for 2-min in the early recovery phase between each interval. Pulmonary gas exchange (V̇O2, V̇CO2, and V̇E), tissue oxygen saturation index (TSI), heart rate (HR), and serum vascular endothelial growth factor concentration (VEGF) were measured. Compared to CON, BFR increased V̇CO2 and V̇E during work bouts (both p < 0.05, dz < 0.5), but there was no effect on V̇O2, TSI, or HR (p > 0.05). In early recovery, BFR decreased TSI, V̇O2, V̇CO2, and V̇E (all p < 0.05, dz > 0.8) versus CON, with no change in HR (p > 0.05). In late recovery, when BFR was released, V̇O2, V̇CO2, V̇E, and HR increased, but TSI decreased versus CON (all p < 0.05, dz > 0.8). There was a greater increase in VEGF at 3-h post-exercise in BFR compared to CON (p < 0.05, dz > 0.8). Incorporating BFR into HIIT recovery phases altered physiological responses compared to exercise alone.

Coconut Water: A Sports Drink Alternative?

Coconut water is used as an alternative to conventional sports drinks for hydration during endurance cycling; however, evidence supporting its use is limited. This study determined if drinking coconut water compared to a sports drink altered cycling performance and physiology. In a randomized crossover trial, 19 experienced male (n = 15) and female (n = 4) cyclists (age 30 ± 9 years, body mass 79 ± 11 kg, V̇O2 peak 55 ± 8 mL·kg-1·min-1) completed two experimental trials, consuming either a commercially available sports drink or iso-calorific coconut water during 90 min of sub-maximal cycling at 70% of their peak power output, followed by a simulated, variable gradient, 20 km time trial. Blood glucose, lactate, sweat loss, and heart rate were monitored throughout the 90 min of sub-maximal cycling, as well as the time trial performance (seconds) and average power (watts). A repeated measures analysis of variance and effect sizes (Cohen's d) analysis were applied. There were no significant differences (p ≥ 0.05) between the treatments for any of the measured physiological or performance variables. Additionally, the effect size analysis showed only trivial (d ≤ 0.2) differences between the treatments for all the measured variables, except blood glucose, which was lower in the coconut water trial compared to the sports drink trial (d = 0.31). Consuming coconut water had a similar effect on the cycling time trial performance and the physiological responses to consuming a commercially available sports drink.

Can physical activity be simplified for health benefit?

AIM: Physical activity (PA) offers protective benefits against at least 25 chronic conditions including psychological stress. The health benefits of PA may be largely attributed to improvements in cardiorespiratory fitness (CRF). However, current guidelines based on PA duration and intensity are controversial, and both are prone to measurement error. We designed a New Zealand specific physical activity frequency and type (PAFT) question, our aims were to examine if PAFT could predict CRF and psychological stress status. METHODS: In experiment one, 20 subjects who regularly perfumed vigorous type PA completed PAFT prior to World Health Organization (WHO) recommended cardiorespiratory fitness (CRF) (VO2Peak) estimation in a controlled exercise laboratory. In experiment two, 81 subjects completed PAFT and a reliable validated measure of stress (the ten-item Perceived Stress Scale (PSS-10)). RESULTS: Vigorous type PA frequency had a strong association (R2=0.71, p<0.01) with VO2Peak and was also the most significant (p<0.01) predictor of low stress. CONCLUSIONS: A simple quick PA type and frequency question predicts CRF and stress status. PA duration and intensity are not required to estimate the health benefits of PA. Two vigorous type PA activities per week can be recommended as a minimum PA dose to decrease risk of stress in similar populations.

Critical Power, Work Capacity, and Recovery Characteristics of Team-Pursuit Cyclists.

PURPOSE: Leading a 4-km team pursuit (TP) requires high-intensity efforts above critical power (CP) that deplete riders' finite work capacity (W'), whereas riders following in the aerodynamic draft may experience some recovery due to reduced power demands. This study aimed to determine how rider ability and CP and W' measures impact TP performance and the extent to which W' can reconstitute during recovery positions in a TP race. METHODS: Three TP teams, each consisting of 4 males, completed individual performance tests to determine their CP and W'. Teams were classified based on their performance level as international (INT), national (NAT), or regional (REG). Each team performed a TP on an indoor velodrome (INT: 3:49.9; NAT: 3:56.7; and REG: 4:05.4; min:s). Ergometer-based TP simulations with an open-ended interval to exhaustion were performed to measure individual ability to reconstitute W' at 25 to 100 W below CP. RESULTS: The INT team possessed higher CP (407 [4] W) than both NAT (381 [13] W) and REG (376 [15] W) (P < .05), whereas W' was similar between teams (INT: 27.2 [2.8] kJ; NAT: 29.3 [2.4] kJ; and REG: 28.8 [1.6] kJ; P > .05). The INT team expended 104% (5%) of their initial W' during the TP and possessed faster rates of recovery than NAT and REG at 25 and 50 W below CP (P < .05). CONCLUSIONS: The CP and rate of W' reconstitution have a greater impact on TP performance than W' magnitude and can differentiate TP performance level.

Validity and reliability of a new field test (Carminatti's test) for soccer players compared with laboratory-based measures.

The aim of this study was to assess the validity (Study 1) and reliability (Study 2) of a novel intermittent running test (Carminatti's test) for physiological assessment of soccer players. In Study 1, 28 players performed Carminatti's test, a repeated sprint ability test, and an intermittent treadmill test. In Study 2, 24 players performed Carminatti's test twice within 72 h to determine test-retest reliability. Carminatti's test required the participants to complete repeated bouts of 5 × 12 s shuttle running at progressively faster speeds until volitional exhaustion. The 12 s bouts were separated by 6 s recovery periods, making each stage 90 s in duration. The initial running distance was set at 15 m and was increased by 1 m at each stage (90 s). The repeated sprint ability test required the participants to perform 7 × 34.2 m maximal effort sprints separated by 25 s recovery. During the intermittent treadmill test, the initial velocity of 9.0 km · h(-1) was increased by 1.2 km · h(-1) every 3 min until volitional exhaustion. No significant difference (P > 0.05) was observed between Carminatti's test peak running velocity and speed at VO(2max) (v-VO(2max)). Peak running velocity in Carminatti's test was strongly correlated with v-VO(2max) (r = 0.74, P < 0.01), and highly associated with velocity at the onset of blood lactate accumulation (r = 0.63, P < 0.01). Mean sprint time was strongly associated with peak running velocity in Carminatti's test (r = -0.71, P < 0.01). The intraclass correlation was 0.94 with a coefficient of variation of 1.4%. In conclusion, Carminatti's test appears to be avalid and reliable measure of physical fitness and of the ability to perform intermittent high-intensity exercise in soccer players.

Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen.

We have previously demonstrated that well-trained subjects who completed a 3 week training programme in which selected high-intensity interval training (HIT) sessions were commenced with low muscle glycogen content increased the maximal activities of several oxidative enzymes that promote endurance adaptations to a greater extent than subjects who began all training sessions with normal glycogen levels. The aim of the present study was to investigate acute skeletal muscle signalling responses to a single bout of HIT commenced with low or normal muscle glycogen stores in an attempt to elucidate potential mechanism(s) that might underlie our previous observations. Six endurance-trained cyclists/triathletes performed a 100 min ride at approximately 70% peak O(2) uptake (AT) on day 1 and HIT (8 x 5 min work bouts at maximal self-selected effort with 1 min rest) 24 h later (HIGH). Another six subjects, matched for fitness and training history, performed AT on day 1 then 1-2 h later, HIT (LOW). Muscle biopsies were taken before and after HIT. Muscle glycogen concentration was higher in HIGH versus LOW before the HIT (390 +/- 28 versus 256 +/- 67 micromol (g dry wt)(1)). After HIT, glycogen levels were reduced in both groups (P < 0.05) but HIGH was elevated compared with LOW (229 +/- 29 versus 124 +/- 41 micromol (g dry wt)(1); P < 0.05). Phosphorylation of 5 AMP-activated protein kinase (AMPK) increased after HIT, but the magnitude of increase was greater in LOW (P < 0.05). Despite the augmented AMPK response in LOW after HIT, selected downstream AMPK substrates were similar between groups. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was unchanged for both groups before and after the HIT training sessions. We conclude that despite a greater activation AMPK phosphorylation when HIT was commenced with low compared with normal muscle glycogen availability, the localization and phosphorylation state of selected downstream targets of AMPK were similar in response to the two interventions.

Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists.

This investigation reports the effects of caffeinated chewing gum on fatigue and hormone response during repeated sprint performance with competitive cyclists. Nine male cyclists (mean ± SD, age 24 ± 7 years, VO(2max) 62.5 ± 5.4 mL kg(-1) min(-1)) completed four high-intensity experimental sessions, consisting of four sets of 30 s sprints (5 sprints each set). Caffeine (240 mg) or placebo was administered via chewing gum following the second set of each experimental session. Testosterone and cortisol concentrations were assayed in saliva samples collected at rest and after each set of sprints. Mean power output in the first 10 sprints relative to the last 10 sprints declined by 5.8 ± 4.0% in the placebo and 0.4 ± 7.7% in the caffeine trials, respectively. The reduced fatigue in the caffeine trials equated to a 5.4% (90% confidence limit ±3.6%, effect size 0.25; ±0.16) performance enhancement in favour of caffeine. Salivary testosterone increased rapidly from rest (~53%) and prior to treatments in all trials. Following caffeine treatment, testosterone increased by a further 12 ± 14% (ES 0.50; ± 0.56) relative to the placebo condition. In contrast, cortisol concentrations were not elevated until after the third exercise set; following the caffeine treatment cortisol was reduced by 21 ± 31% (ES -0.30; ± 0.34) relative to placebo. The acute ingestion of caffeine via chewing gum attenuated fatigue during repeated, high-intensity sprint exercise in competitive cyclists. Furthermore, the delayed fatigue was associated with substantially elevated testosterone concentrations and decreased cortisol in the caffeine trials.

A Comparison of Different Prerace Warm-Up Strategies on 1-km Cycling Time-Trial Performance.

PURPOSE: Ischemic preconditioning (IPC) and postactivation potentiation (PAP) are warm-up strategies proposed to improve high-intensity sporting performance. However, only few studies have investigated the benefits of these strategies compared with an appropriate control (CON) or an athlete-selected (SELF) warm-up protocol. Therefore, this study examined the effects of 4 different warm-up routines on 1-km time-trial (TT) performance with competitive cyclists. METHODS: In a randomized crossover study, 12 well-trained cyclists (age 32 [10] y, mass 77.7 [4.6] kg, peak power output 1141 [61] W) performed 4 different warm-up strategies-(CON) 17 minutes CON only, (SELF) a self-determined warm-up, (IPC) IPC + CON, or (PAP) CON + PAP-prior to completing a maximal-effort 1-km TT. Performance time and power, quadriceps electromyograms, muscle oxygen saturation (SmO2), and blood lactate were measured to determine differences between trials. RESULTS: There were no significant differences (P > .05) in 1-km performance time between CON (76.9 [5.2] s), SELF (77.3 [6.0] s), IPC (77.0 [5.5] s), or PAP (77.3 [5.9] s) protocols. Furthermore, there were no significant differences in mean or peak power output between trials. Finally, electromyogram activity, SmO2, and recovery blood lactate concentration were not different between conditions. CONCLUSIONS: Adding IPC or PAP protocols to a short CON warm-up appears to provide no additional benefit to 1-km TT performance with well-trained cyclists and is therefore not recommended. Furthermore, additional IPC and PAP protocols had no effect on electromyograms and SmO2 values during the TT or peak lactate concentration during recovery.

The Effects of Different Forms of Caffeine Supplement on 5-km Running Performance.

PURPOSE: Caffeine is frequently used by athletes as an ergogenic aid. Various alternate forms of caffeine administration are available, which may produce different effects. This investigation compares the effects of different forms of caffeine supplementation on 5-km running performance, and the relationship between athlete ability and degree of enhancement attained. METHODS: Fourteen amateur runners completed a series of self-paced outdoor time trials following unknown ingestion of a placebo (P) or one of 3 alternate forms of caffeine supplement. Trials were randomized in a crossover design with caffeine (approximately 3-4.5 mg·kg-1) administered 15 minutes before each trial via chewing gum (CG), dissolvable mouth strips (CS), or tablet (CT). RESULTS: Compared with P, all caffeine supplements led to worthwhile enhancements in running performance with a mean (±95% confidence limit) overall effect across all supplements of 1.4% ± 0.9%. Individual caffeine treatment effects (CG = 0.9% ± 1.4%, CS = 1.2% ± 1.0%, and CT = 2.0% ± 1.1%) were not significantly different (P > .05) from each other; however, CT trials produced the largest gain and was significantly different (P = .02) compared with P. There was no significant difference in heart rate or rate of perceived exertion across the performance trials. The magnitude of caffeine enhancement was also strongly correlated (r = .87) with no-treatment performance time. CONCLUSIONS: The findings showed that irrespective of delivery form, moderate dose of caffeine supplementation produces worthwhile gains in 5-km running performance compared with a P. Furthermore, the magnitude of caffeine enhancement is highly individualized, but it appears related to athlete performance ability.

A comparison of acute glycaemic responses to accumulated or single bout walking exercise in apparently healthy, insufficiently active adults.

OBJECTIVES: To investigate the acute glyacaemic response to accumulated or single bout walking exercise in apparently healthy adults. DESIGN: Three arm, randomised crossover control study. METHODS: Ten adults (age: 50±12.6 y; BMI 29.0±5.4kgm-2) completed three separate trials comprising three 10-min walking bouts after breakfast, lunch, and dinner (APPW), a single 30-min walking bout after dinner only (CPPW), or a no-exercise control (NOEX). Participants walked on a treadmill at a moderate intensity of 55%-70% heart rate reserve. Two-hour postprandial glucose response was assessed using a continuous glucose monitor. RESULTS: There was a difference in the pattern of the glucose response between the trials during the two hours following dinner (p<0.001). Postprandial dinner glucose concentrations were not different between APPW and CPPW but were up to 1.01mmolL-1 lower than NOEX (partial eta2=0.21, p=0.041). CONCLUSIONS: Ten minutes of moderate intensity walking completed 30min after each meal lowers postprandial dinner glucose concentrations in comparison to no-exercise, and reduces glucose by a similar magnitude as a single 30-min bout after the evening meal. Short bouts of exercise after each meal may be recommended to minimise glucose elevations after dinner that might increase risk of cardiometabolic disease.

Effects of low- vs. high-cadence interval training on cycling performance.

High-resistance interval training produces substantial gains in sprint and endurance performance of cyclists in the competitive phase of a season. Here, we report the effect of changing the cadence of the intervals. We randomized 18 road cyclists to 2 groups for 4 weeks of training. Both groups replaced part of their usual training with 8 30-minute sessions consisting of sets of explosive single-leg jumps alternating with sets of high-intensity cycling sprints performed at either low cadence (60-70 min(-1)) or high cadence (110-120 min(-1)) on a training ergometer. Testosterone concentration was assayed in saliva samples collected before and after each session. Cycle ergometry before and after the intervention provided measures of performance (mean power in a 60-s time trial, incremental peak power, 4-mM lactate power) and physiologic indices of endurance performance (maximum oxygen uptake, exercise economy, fractional utilization of maximum oxygen uptake). Testosterone concentration in each session increased by 97% +/- 39% (mean +/- between-subject SD) in the low-cadence group but by only 62% +/- 23% in the high-cadence group. Performance in the low-cadence group improved more than in the high-cadence group, with mean differences of 2.5% (90% confidence limits, +/-4.8%) for 60-second mean power, 3.6% (+/-3.7%) for peak power, and 7.0% (+/-5.9%) for 4-mM lactate power. Maximum oxygen uptake showed a corresponding mean difference of 3.2% (+/-4.2%), but differences for other physiologic indices were unclear. Correlations between changes in performance and physiology were also unclear. Low-cadence interval training is probably more effective than high-cadence training in improving performance of well-trained competitive cyclists. The effects on performance may be related to training-associated effects on testosterone and to effects on maximum oxygen uptake.

Supplementing regular training with short-duration sprint-agility training leads to a substantial increase in repeated sprint-agility performance with national level badminton players.

Repeated-agility sprint ability is an important performance characteristic of badminton players. However, it is unclear whether regular badminton training is sufficient to improve repeated-agility sprint ability or whether supplementary training is required. Therefore, our aim was to investigate whether supplementing regular group training with short sessions of badminton-specific agility-sprint training conferred any greater changes in performance than regular training alone. Twelve national level badminton players completed a set of performance tests in the week before and after a 4-week training period. Performance tests consisted of 10- and 20-meter sprints, a multistage fitness test, a 300-meter shuttle run, and a novel badminton sprint protocol. After pretesting, pair-matched participants were randomly assigned into regular or supplementary training groups. Both groups undertook regular national squad training consisting of 4 2-hour sessions per week. In addition, the supplementary group completed a high-intensity sprint-training regime consisting of 7 to 15 repeats of badminton-specific sprints twice per week. Relative to control, the supplementary training group reported improvements (mean +/- 90% confidence limits) in the 300-meter shuttle run (2.4% +/- 2.7%) and badminton sprint protocol (3.6% +/- 2.6%). However, there were no substantial difference in either the 10-meter (-0.3% +/- 2.1%) or 20-meter (-0.6% +/- 1.8%) sprint or the multistage fitness test (0.0% +/- 2.7%). Supplementing regular training with sessions of short-duration sprint training appears to lead to worthwhile increases in repeated-agility sprint performance with national level badminton players.

Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens.

We determined the effects of a cycle training program in which selected sessions were performed with low muscle glycogen content on training capacity and subsequent endurance performance, whole body substrate oxidation during submaximal exercise, and several mitochondrial enzymes and signaling proteins with putative roles in promoting training adaptation. Seven endurance-trained cyclists/triathletes trained daily (High) alternating between 100-min steady-state aerobic rides (AT) one day, followed by a high-intensity interval training session (HIT; 8 x 5 min at maximum self-selected effort) the next day. Another seven subjects trained twice every second day (Low), first undertaking AT, then 1-2 h later, the HIT. These training schedules were maintained for 3 wk. Forty-eight hours before and after the first and last training sessions, all subjects completed a 60-min steady-state ride (60SS) followed by a 60-min performance trial. Muscle biopsies were taken before and after 60SS, and rates of substrate oxidation were determined throughout this ride. Resting muscle glycogen concentration (412 +/- 51 vs. 577 +/- 34 micromol/g dry wt), rates of whole body fat oxidation during 60SS (1,261 +/- 247 vs. 1,698 +/- 174 micromol.kg(-1).60 min(-1)), the maximal activities of citrate synthase (45 +/- 2 vs. 54 +/- 1 mmol.kg dry wt(-1).min(-1)), and beta-hydroxyacyl-CoA-dehydrogenase (18 +/- 2 vs. 23 +/- 2 mmol.kg dry wt(-1).min(-1)) along with the total protein content of cytochrome c oxidase subunit IV were increased only in Low (all P < 0.05). Mitochondrial DNA content and peroxisome proliferator-activated receptor-gamma coactivator-1alpha protein levels were unchanged in both groups after training. Cycling performance improved by approximately 10% in both Low and High. We conclude that compared with training daily, training twice every second day compromised high-intensity training capacity. While selected markers of training adaptation were enhanced with twice a day training, the performance of a 1-h time trial undertaken after a 60-min steady-state ride was similar after once daily or twice every second day training programs.

The effects of interval-exercise duration and intensity on oxygen consumption during treadmill running.

The magnitude of improvement in peak oxygen uptake (V(o)(2peak))) and performance to an exercise training regime is related to the V(o)(2) of prior accumulated exercise training bouts. However, it is unclear whether constant rate training (CRT) or interval training (INT) preferentially alters the V(o)(2) of running exercise. Therefore, the purpose of this study was to compare the acute V(o)(2) response to constant, and interval training sessions. Consequently, this study compared the mean average V(o)(2) of 17 moderately trained participants to a 20-min CRT and two different 20min INT treadmill runs. Participants completed three treatments (twice) in random order over 3 weeks. In 1min INT participants completed 10x1min efforts at the velocity corresponding to V(o)(2peak) (V(peak)) interspersed with 10x1min efforts at 0.5V(peak). In the 2min INT, participants completed 5x2min efforts at the V(peak) interspersed with 5x2min efforts at 0.5 at V(peak). In CRT participants ran at a velocity equivalent to the mean velocity of INT (75% V(peak)). Mean average V(o)(2) for 2min INT, 1min INT and CRT were, respectively, 3200+/-661; 3076+/-6041; 2909+/-584mlmin(-1). Both INT sessions resulted in a significantly higher mean average V(o)(2) than CRT. Furthermore, 2min INT resulted in 90% of V(o)(2peak) being exceeded more frequently than 1min INT. We conclude that INT serves as a more potent stimulus for improvement in V(o)(2peak) and subsequent endurance performance than CRT.

Caffeine has a small effect on 5-km running performance of well-trained and recreational runners.

The purpose of this study was to investigate if caffeine ingestion improves 5-km time-trial performance in well-trained and recreational runners. Using a double-blind placebo-controlled design, 15 well-trained and 15 recreational runners completed two randomized 5-km time-trials, after ingestion of either 5mgkg(-1) of caffeine or a placebo. Caffeine ingestion significantly improved 5-km running performance in both the well-trained and recreational runners. In comparison to the placebo trial, the caffeine trial resulted in 1.1% (90% CI 0.4-1.6) and 1.0% (0.2-2%) faster times for the well-trained and recreational runners. Reliability testing of the recreational runners indicated a test-retest error of measurement of 1.4%. We conclude that caffeine ingestion is likely to produce small but significant gains in 5-km running performance for both well-trained and recreational runners.