The effect of fatigue on first stance phase kinetics during acceleration sprint running in professional football players.

Nineteen professional football players (Age: 26±5 years; Height: 1.84±0.08 m; Mass: 83.4±8.9 kg) completed three x 30 m maximal acceleration sprints from a standing start before completing the Yo-Yo intermittent recovery test level 1. Three x 30 m maximal acceleration sprints were then repeated post-fatigue. Light gates recorded sprint times from 0-5 m, 0-10 m, 0-15 m and 0-30 m. Force platforms collected ground reaction force of the first stance phase of the sprint run. Differences between pre- and post-fatigue were observed in the sprint times over 0-15 m (P = 0.015; CI [0.007, 0.110]) and 0-30 m (P = 0.004; CI [0.056, 0.234]). Peak medial-lateral ground reaction force was lower (P = 0.045; CI [-0.146, -0.005]) post- than pre-fatigue. The ratio of force were significantly different between pre- and post-fatigue for the medial-lateral and anterior-posterior comparison (P = 0.017; CI [-0.063, -0.010]), and the medial-lateral and vertical comparison (P = 0.012; CI [-0.036, -0.007]). Football players altered their sprint mechanics to reduce medial-lateral loading and orient the force in an increased anteroposterior and vertical direction in order to maintain 0-10 m sprint performance. Practitioners should observe medial-lateral force contributions and improve sprint technical efficacy.

Whole body precooling attenuates the extracellular HSP72, IL-6 and IL-10 responses after an acute bout of running in the heat.

The impact of whole-body precooling on the extracellular heat shock protein 72 (eHSP72) and cytokine responses to running in the heat is undefined. The aim of this study was to determine whether precooling would attenuate post-exercise eHSP72 and cytokine responses. Eight male recreational runners completed two 90-minute bouts of running at 65% [Formula: see text]O2max in 32 ± 0.9°C and 47 ± 6 % relative humidity (RH) preceded by either 60-minutes of precooling in 20.3 ± 0.3°C water (COOL) or 60 min rest in an air-conditioned laboratory (20.2 ± 1.7°C, 60 ± 3% RH; CON). eHSP72, TNF-α, IL-6, IL-10 IL-1ra were determined before and immediately after exercise. The elevation in post-exercise eHSP72 was attenuated after COOL (+0.04 ± 0.10 ng.mL-1) compared to CON (+ 0.29 ± 0.26 ng.mL-1;P < 0.001). No changes in TNF-α were observed at any stage. COOL reduced the absolute post-exercise change in IL-6 (P = 0.011) and IL-10 (P = 0.03) compared to CON. IL-1ra followed this trend (P = 0.063). A precooling-induced attenuation of eHSP72 and proinflammatory cytokines may aid recovery during multi-day sporting events, but could be counterproductive if a training response or adaptation to environmental stress is a desired outcome.

Pre-cooling moderately enhances visual discrimination during exercise in the heat.

Pre-cooling has been reported to attenuate the increase in core temperature, although, information regarding the effects of pre-cooling on cognitive function is limited. The present study investigated the effects of pre-cooling on visual discrimination during exercise in the heat. Eight male recreational runners completed 90 min of treadmill running at 65% [Formula: see text]2max in the heat [32.4 ± 0.9°C and 46.8 ± 6.4% relative humidity (r.h.)] on two occasions in a randomised, counterbalanced crossover design. Participants underwent pre-cooling by means of water immersion (20.3 ± 0.3°C) for 60 min or remained seated for 60 min in a laboratory (20.2 ± 1.7°C and 60.2 ± 2.5% r.h.). Rectal temperature (Trec) and mean skin temperature (Tskin) were monitored throughout the protocol. At 30-min intervals participants performed a visual discrimination task. Following pre-cooling, Trec (P = 0.040; [Formula: see text] = 0.48) was moderately lower at 0 and 30 min and Tskin (P = 0.003; [Formula: see text] = 0.75) lower to a large extent at 0 min of exercise. Visual discrimination was moderately more accurate at 60 and 90 min of exercise following pre-cooling (P = 0.067; [Formula: see text] = 0.40). Pre-cooling resulted in small improvements in visual discrimination sensitivity (F1,7 = 2.188; P = 0.183; [Formula: see text] = 0.24), criterion (F1,7 = 1.298; P = 0.292; [Formula: see text] = 0.16) and bias (F1,7 = 2.202; P = 0.181; [Formula: see text] = 0.24). Pre-cooling moderately improves visual discrimination accuracy during exercise in the heat.

Effects of increasing and decreasing physiological arousal on anticipation timing performance during competition and practice.

The aim of this study was to investigate if the effects of changes in physiological arousal on timing performance can be accurately predicted by the catastrophe model. Eighteen young adults (8 males, 10 females) volunteered to participate in the study following ethical approval. After familiarisation, coincidence anticipation was measured using the Bassin Anticipation Timer under four incremental exercise conditions: Increasing exercise intensity and low cognitive anxiety, increasing exercise intensity and high cognitive anxiety, decreasing exercise intensity and low cognitive anxiety and decreasing exercise intensity and high cognitive anxiety. Incremental exercise was performed on a treadmill at intensities of 30%, 50%, 70% and 90% heart rate reserve (HRR) respectively. Ratings of cognitive anxiety were taken at each intensity using the Mental Readiness Form 3 (MRF3) followed by performance of coincidence anticipation trials at speeds of 3 and 8 mph. Results indicated significant condition × intensity interactions for absolute error (AE; p = .0001) and MRF cognitive anxiety intensity scores (p = .05). Post hoc analysis indicated that there were no statistically significant differences in AE across exercise intensities in low-cognitive anxiety conditions. In high-cognitive anxiety conditions, timing performance AE was significantly poorer and cognitive anxiety higher at 90% HRR, compared to the other exercise intensities. There was no difference in timing responses at 90% HRR during competitive trials, irrespective of whether exercise intensity was increasing or decreasing. This study suggests that anticipation timing performance is negatively affected when physiological arousal and cognitive anxiety are high.

Circulatory endotoxin concentration and cytokine profile in response to exertional-heat stress during a multi-stage ultra-marathon competition.

Exertional-heat stress has the potential to disturb intestinal integrity, leading to enhanced permeability of enteric pathogenic micro-organisms and associated clinical manifestations. The study aimed to determine the circulatory endotoxin concentration and cytokine profile of ultra-endurance runners (UER, n=19) and a control group (CON, n=12) during a five stage 230km ultra-marathon (mean ± SD: 27h38min ± 3h55min) conducted in hot and dry environmental conditions (30ºC to 40ºC and 31% to 40% relative humidity). Body mass and tympanic temperature were measured, and venous blood samples were taken before (pre-stage) and immediately after (post-stage) each stage of the ultra-marathon for the analysis of gram-negative bacterial endotoxin, C-reactive protein, cytokine profile (IL-6, IL-1ß, TNF-α, IFN-γ, IL-10, and IL- 1ra), and plasma osmolality. Gastrointestinal symptoms and perceptive thermal tolerance rating were also monitored throughout competition. Mean exercise-induced body mass loss over the five stages ranged 1.0% to 2.5%. Pre- and poststage plasma osmolality in UER ranged277 to 282mOsmol/kg and 286 to 297 mOsmol/kg, respectively. Pre-stage concentrations of endotoxin (peak: 21% at Stage 5), C-reactive protein (889% at Stage 3), IL-6 (152% at Stage 2), IL-1ß (95% at Stage 5), TNF-α (168% at Stage 5), IFN-γ (102% at Stage 5),IL-10 (1271% at Stage 3), and IL-1ra (106% at Stage 5) increased as the ultra-marathon progressed in UER; while no changes in CON were observed (except for IL-1ß, 71% at Stage 5). Pre- to post-stage increases were observed for endotoxin (peak: 22% at Stage 3), C-reactive protein (25% at Stage 1), IL-6 (238% at Stage 1), IL-1ß (64% at Stage 1), TNF-α (101% at Stage 1), IFN-γ (39% at Stage 1), IL-10 (1100% at Stage 1), and IL-1ra(207% at Stage 1) concentrations in UER. Multi-stage ultra-marathon competition in the heat resulted in a modest circulatory endotoxaemia accompanied by a pronounced pro-inflammatory cytokinaemia by post-Stage 1, both of which were sustained throughout competition at rest (pre-stage) and after stage completion. Compensatory anti-inflammatory responses and other external factors (i.e., training status, cooling strategies, heat acclimatization, nutrition and hydration) may have contributed towards limiting the extent of pro-inflammatory responses in the current scenario.

Mental fatigue negatively influences manual dexterity and anticipation timing but not repeated high-intensity exercise performance in trained adults.

This study examined the impact of a period of mental fatigue on manual dexterity, anticipation timing and repeated high intensity exercise performance. Using a randomised, repeated measures experimental design, eight physically trained adults (mean age = 24.8 ± 4.1 years) undertook a 40 minute vigilance task to elicit mental fatigue or a control condition followed by four repeated Wingate anaerobic performance tests. Pre, post fatigue/control and post each Wingate test, manual dexterity (Seconds), coincidence anticipation (absolute error) were assessed. A series of two (condition) by six (time) ways repeated measures ANOVAs indicated a significant condition by time interactions for manual dexterity time (p = 0.021) and absolute error (p = 0.028). Manual dexterity and coincidence anticipation were significantly poorer post mental fatigue compared with control. There were no significant differences in mean power between conditions or across trials (all p > 0.05).

Perturbed energy balance and hydration status in ultra-endurance runners during a 24 h ultra-marathon.

The present study aimed to assess the adequacy of energy, macronutrients and water intakes of ultra-endurance runners (UER) competing in a 24 h ultra-marathon (distance range: 122-208 km). The ad libitum food and fluid intakes of the UER (n 25) were recorded throughout the competition and analysed using dietary analysis software. Body mass (BM), urinary ketone presence, plasma osmolality (POsmol) and volume change were determined at pre- and post-competition time points. Data were analysed using appropriate t tests, with significance set at P <0·05. The total energy intake and expenditure of the UER were 20 (sd 12) and 55 (sd 11) MJ, respectively (control (CON) (n 17): 12 (sd 1) and 14 (sd 5) MJ, respectively). The protein, carbohydrate and fat intakes of the UER were 1·1 (sd 0·4), 11·3 (sd 7·0) and 1·5 (sd 0·7) g/kg BM, respectively. The rate of carbohydrate intake during the competition was 37 (sd 24) g/h. The total water intake of the UER was 9·1 (sd 4·0) litres (CON: 2·1 (sd 1·0) litres), while the rate of water intake was 378 (sd 164) ml/h. Significant BM loss occurred at pre- to post-competition time points (P =0·001) in the UER (1·6 (sd 2·0) %). No significant changes in POsmol values were observed at pre- (285 (sd 11) mOsmol/kg) to post-competition (287 (sd 10) mOsmol/kg) time points in the UER and were lower than those recorded in the CON group (P <0·05). However, plasma volume (PV) increased at post-competition time points in the UER (10·2 (sd 9·7) %; P <0·001). Urinary ketones were evident in the post-competition samples of 90 % of the UER. Energy deficit was observed in all the UER, with only one UER achieving the benchmark recommendations for carbohydrate intake during endurance exercise. Despite the relatively low water intake rates recorded in the UER, hypohydration does not appear to be an issue, considering increases in PV values observed in the majority (80 %) of the UER. Population-specific dietary recommendations may be beneficial and warranted.

The effect of green exercise on blood pressure, heart rate and mood state in primary school children.

The aim of this study was exploratory and sought to examine the effect on blood pressure (BP), heart rate (HR) and mood state responses in primary school children of moderate intensity cycling whilst viewing a green environment compared to exercise alone. Following ethics approval and parental informed consent, 14 children (seven boys, seven girls, Mean age ± SD = 10 ± 1 years) undertook two, 15 min bouts of cycling at a moderate exercise intensity in a counterbalanced order. In one bout they cycled whilst viewing a film of cycling in a forest setting. In the other condition participants cycled with no visual stimulus. Pre-, immediately post-exercise and 15 min post-exercise, BP, HR and Mood state were assessed. Analysis of variance, indicated significant condition X time interaction for SBP (p = 0.04). Bonferroni post-hoc pairwise comparisons indicated that systolic blood pressure (SBP) 15 min post exercise was significantly lower following green exercise compared to the control condition (p = 0.01). There were no significant differences in diastolic blood pressure (DBP) (all p > 0.05). HR immediately post exercise was significantly higher than HR pre exercise irrespective of green exercise or control condition (p = 0.001). Mood scores for fatigue were significantly higher and scores for vigor lower 15 min post exercise irrespective of green exercise or control condition (both p = 0.0001). Gender was not significant in any analyses (p > 0.05). Thus, the present study identifies an augmented post exercise hypotensive effect for children following green exercise compared to exercise alone.

The effect of moderate and high-intensity fatigue on groundstroke accuracy in expert and non-expert tennis players.

Exploring the effects of fatigue on skilled performance in tennis presents a significant challenge to the researcher with respect to ecological validity. This study examined the effects of moderate and high-intensity fatigue on groundstroke accuracy in expert and non-expert tennis players. The research also explored whether the effects of fatigue are the same regardless of gender and player's achievement motivation characteristics. 13 expert (7 male, 6 female) and 17 non-expert (13 male, 4 female) tennis players participated in the study. Groundstroke accuracy was assessed using the modified Loughborough Tennis Skills Test. Fatigue was induced using the Loughborough Intermittent Tennis Test with moderate (70%) and high-intensities (90%) set as a percentage of peak heart rate (attained during a tennis-specific maximal hitting sprint test). Ratings of perceived exertion were used as an adjunct to the monitoring of heart rate. Achievement goal indicators for each player were assessed using the 2 x 2 Achievement Goals Questionnaire for Sport in an effort to examine if this personality characteristic provides insight into how players perform under moderate and high-intensity fatigue conditions. A series of mixed ANOVA's revealed significant fatigue effects on groundstroke accuracy regardless of expertise. The expert players however, maintained better groundstroke accuracy across all conditions compared to the novice players. Nevertheless, in both groups, performance following high-intensity fatigue deteriorated compared to performance at rest and performance while moderately fatigued. Groundstroke accuracy under moderate levels of fatigue was equivalent to that at rest. Fatigue effects were also similar regardless of gender. No fatigue by expertise, or fatigue by gender interactions were found. Fatigue effects were also equivalent regardless of player's achievement goal indicators. Future research is required to explore the effects of fatigue on performance in tennis using ecologically valid designs that mimic more closely the demands of match play. Key PointsGroundstroke accuracy under moderate-intensity fatigue is equivalent to performance at rest.Groundstroke accuracy declines significantly in both expert (40.3% decline) and non-expert (49.6%) tennis players following high-intensity fatigue.Expert players are more consistent, hit more accurate shots and fewer out shots across all fatigue intensities.The effects of fatigue on groundstroke accuracy are the same regardless of gender and player's achievement goal indicators.

Salivary antimicrobial protein responses during multistage ultramarathon competition conducted in hot environmental conditions.

Prolonged strenuous exercise is commonly reported to depress oral-respiratory immune status and increase the incidence of upper respiratory symptoms. This novel investigation aimed to determine the salivary antimicrobial responses and hydration status of ultraendurance runners (n = 23) during a 230-km multistage ultramarathon conducted in hot ambient conditions (32-40 °C). Body mass was measured and unstimulated saliva and venous blood samples were taken before and after each stage of the ultramarathon. Ad libitum fluid intake was permitted throughout each race day. Upper respiratory symptoms were monitored during and until 4 weeks after race completion. Samples were analyzed for salivary immunoglobulin A (IgA), lysozyme, α-amylase, and cortisol, as well as for plasma and saliva osmolality. Mean exercise-induced body mass loss over the 5 stages ranged from 1.3% to 2.4%. Overall mean pre- and post-stage plasma osmolality measurements in the ultraendurance runners were 279 ± 14 mOsmol·kg(-1) and 293 ± 15 mOsmol·kg(-1), respectively. Decreases in saliva flow rate (overall change 22%) and post-stage increases in saliva osmolality (36%) were observed in the ultraendurance runners during the ultramarathon. Reduced salivary IgA (32%) (p < 0.001 vs. pre-stage salivary IgA), enhanced salivary α-amylase (187%) (p < 0.001 vs. pre-stage salivary α-amylase), and no change in salivary lysozyme secretion rates were observed in the ultraendurance runners throughout the ultramarathon. Only 1 ultraendurance runner reported upper respiratory symptoms during and 1 month after competition. Observed depressions in salivary IgA secretion rates were offset by favourable increases in salivary α-amylase and unchanged lysozyme responses in the majority of runners during the competition. Ensuring euhydration throughout a multistage ultramarathon competition in the heat may play a role in protecting the upper respiratory tract.

Peak-power estimation equations in 12- to 16-year old children: comparing linear with allometric models.

This study examined the efficacy of peak-power estimation equations in children using force platform data and determined whether allometric modeling offers a sounder alternative to estimating peak power in pediatric samples. Ninety one boys and girls aged 12-16 years performed 3 countermovement jumps (CMJ) on a force platform. Estimated peak power (PP(est)) was determined using the Harman et al., Sayers SJ, Sayers CMJ, and Canavan and Vescovi equations. All 4 equations were associated with actual peak power (r = 0.893-0.909, all p < .01). There were significant differences between PP(est) using the Harman et al., Sayers SJ, and Sayers CMJ equations (p < .05) and actual peak power (PP(actual)). ANCOVA also indicated sex and age effect for PPactual (p < .01). Following a random two-thirds to one-third split of participants, an additive linear model (p = .0001) predicted PPactual (adjusted R(2) = .866) from body mass and CMJ height in the two-thirds split (n = 60). An allometric model using CMJ height, body mass, and age was then developed with this sample, which predicted 88.8% of the variance in PP(actual) (p < .0001, adjusted R(2) = .888). The regression equations were cross-validated using the one-third split sample (n = 31), evidencing a significant positive relationship (r = .910, p = .001) and no significant difference (p = .151) between PP(actual) and PP(est) using this equation. The allometric and linear models determined from this study provide accurate models to estimate peak power in children.

The effect of a caffeinated energy drink on various psychological measures during submaximal cycling.

Caffeine containing energy drinks is commonly consumed in the belief that it will enhance the quality of an exercise session and enhance mood. However, studies examining their efficacy are sparse. The aim of this study was to examine the effect of a caffeinated energy drink on leg pain perception, perceived exertion, mood state and readiness to invest effort pre, during and post 60 min cycling exercise. Fourteen active individuals (7 males, 7 females, mean age ± S.D.=23.5 ± 3.5 years), completed two 60 min cycling trials at an intensity of 60% VO2 max preceded by ingestion of solutions containing either a caffeinated energy drink or placebo using a double-blind, deceptive, crossover design. During exercise, RPE (6-20 scale), leg pain (0-10 scale), heart rate (HR) and blood lactate (Bla) were recorded. Participants also completed measures of mood state and readiness to invest physical effort (RTIPE) pre- and post-exercise. Repeated measures analysis of variance was used to assess differences in all variables and across time and treatments, with gender used as a between subjects variable. Results indicate that HR was significantly higher (P=.002) from 30 to 60 min and RPE (P=.0001) and pain perception (P=.0001) were significantly lower from 20 to 60 min in the energy drink condition compared to placebo. Bla was significantly higher (P=.021) in the last 15 min of the energy drink trial and RTIPE (P=.001) increased significantly more from pre-ingestion to pre-exercise post-ingestion in the energy drink condition compared to placebo. No gender differences were evident (P>.05). The data revealed positive effects of energy drink ingestion on perception of exertion, leg muscle pain perception and readiness to invest effort during submaximal cycling in active adults.

Water and sodium intake habits and status of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment: an observational field based study.

BACKGROUND: Anecdotal evidence suggests ultra-runners may not be consuming sufficient water through foods and fluids to maintenance euhydration, and present sub-optimal sodium intakes, throughout multi-stage ultra-marathon (MSUM) competitions in the heat. Subsequently, the aims were primarily to assess water and sodium intake habits of recreational ultra-runners during a five stage 225 km semi self-sufficient MSUM conducted in a hot ambient environment (Tmax range: 32°C to 40°C); simultaneously to monitor serum sodium concentration, and hydration status using multiple hydration assessment techniques. METHODS: Total daily, pre-stage, during running, and post-stage water and sodium ingestion of ultra-endurance runners (UER, n = 74) and control (CON, n = 12) through foods and fluids were recorded on Stages 1 to 4 by trained dietetic researchers using dietary recall interview technique, and analysed through dietary analysis software. Body mass (BM), hydration status, and serum sodium concentration were determined pre- and post-Stages 1 to 5. RESULTS: Water (overall mean (SD): total daily 7.7 (1.5) L/day, during running 732 (183) ml/h) and sodium (total daily 3.9 (1.3) g/day, during running 270 (151) mg/L) ingestion did not differ between stages in UER (p < 0.001 vs. CON). Exercise-induced BM loss was 2.4 (1.2)% (p < 0.001). Pre- to post-stage BM gains were observed in 26% of UER along competition. Pre- and post-stage plasma osmolality remained within normal clinical reference range (280 to 303 mOsmol/kg) in the majority of UER (p > 0.05 vs. CON pre-stage). Asymptomatic hyponatraemia (<135 mmol/L) was evident pre- and post-stage in n = 8 UER, corresponding to 42% of sampled participants. Pre- and post-stage urine colour, urine osmolality and urine/plasma osmolality ratio increased (p < 0.001) as competition progressed in UER, with no change in CON. Plasma volume and extra-cellular water increased (p < 0.001) 22.8% and 9.2%, respectively, from pre-Stage 1 to 5 in UER, with no change in CON. CONCLUSION: Water intake habits of ultra-runners during MSUM conducted in hot ambient conditions appear to be sufficient to maintain baseline euhydration levels. However, fluid over-consumption behaviours were evident along competition, irrespective of running speed and gender. Normonatraemia was observed in the majority of ultra-runners throughout MSUM, despite sodium ingestion under benchmark recommendations.

Peak power prediction in junior basketballers: comparing linear and allometric models.

Equations, commonly used to predict peak power from jump height, have relied on linear additive models that are biologically unsound beyond the range of observations because of high negative intercept values. This study explored the utility of allometric multiplicative modeling to better predict peak power in adolescent basketball players. Seventy-seven elite junior basketball players (62 adolescent boys, 15 adolescent girls, age = 16.8 ± 0.8 years) performed 3 counter movement jumps (CMJs) on a force platform. Both linear and multiplicative models were then used to determine their efficacy. Four previously published linear equations were significantly associated with actual peak power (all p < 0.01), although here were significant differences between actual and estimated peak power using the SJ and CMJ equations by Sayers (both p < 0.001). Allometric modeling was used to determine an alternative biologically sound equation which was more strongly associated with (r = 0.886, p < 0.001), and not significantly different to (p > 0.05), actual peak power and predicted 77.9% of the variance in actual peak power (adjusted R = 0.779, p < 0.001). Exponents close to 1 for body mass and CMJ height indicated that peak power could also be determined from the product of body mass and CMJ height. This equation was significantly associated (r = 0.871, p < 0.001) with, and not significantly different to, actual peak power (adjusted R = 0.756, p > 0.05) and offered a more accurate estimation of peak power than previously validated linear additive models examined in this study. The allometric model determined from this study or the multiplicative model (body mass × CMJ height) provides biologically sound models to accurately estimate peak power in elite adolescent basketballers that are more accurate than equations based on linear additive models.

Placebo effects of caffeine on short-term resistance exercise to failure.

PURPOSE: This study examined the placebo effect of caffeine on number of repetitions (reps), rating of perceived exertion (RPE), blood pressure (BP), and peak heart rate (PHR) during resistance-training exercise with repetitions (reps) performed to volitional failure. METHODS: Following determination of 1-rep maximum in single-leg leg extension, 15 males performed reps to failure at 60% 1-RM in 3 conditions: control, perceived caffeine condition, and perceived placebo condition presented in a randomized order. Participants were informed they would ingest 250 mL of solution that contained either 3 mg.kg(-1) caffeine or 3 mg.kg(-1) placebo 1 h before each exercise trial. A deceptive protocol was employed and subjects consumed a placebo solution in both conditions. During each condition, total reps, RPE for the active muscle and overall body, and PHR were recorded. RESULTS: Subjects completed 2 more reps when they perceived they had ingested caffeine. RPE was significantly (P=.04) lower in the perceived caffeine and control conditions and RPE for the active muscle was significantly higher across all conditions compared with RPE for the overall body. No substantial differences were evident in PHR across conditions. CONCLUSIONS: Results of this study are similar to studies of actual caffeine ingestion. However, the perception of consuming a substance that purportedly enhances performance is sufficient enough to enable individuals to complete a greater number of reps to failure during short-term resistance exercise.