Effect of the menstrual cycle on performance of intermittent, high-intensity shuttle running in a hot environment

The present study examined the impact of the menstrual cycle and oral contraceptive use on performance of high intensity intermittent running in the heat [31.0 (0.2) oC; 23.1 (0.9) % RH]. Seven normally menstruating women (NM) and 8 oral contraceptive (OC) users participated in the study. Two trials were undertaken near the predicted mid-point of the follicular (FT) and luteal (LT) phases of the menstrual cycle and the equivalent days for the oral contraceptive users. Basal serum progesterone concentrations were higher during the LT for the NM group [FT: 2.42 (0.28) vs. LT: 25.96 (11.28) nmol.l-1; P<0.05], but were not different for the OC [1-14: 2.79 (0.38) vs. 15-28: 2.61 (0.32) nmol.l-1]. There were no differences in distance run between menstrual cycle phases or between the normally menstruating and oral contraceptive groups [NM FT: 6257 (1401) vs. LT: 5861 (1035) m]. However the OC ran further in the days 15-28 compared to days 1-14 [OC 1-14: 5481 (612) vs 15-28: 6615 (893) m, P<0.05]. For the NM, rectal temperature, perceived exertion, estimated SR, serum growth hormone, plasma lactate, ammonia and glucose did not differ between phases of the menstrual cycle. For the OC, heart rate, perceived exertion, sweat rate, plasma lactate and ammonia did not differ between days 1- 14 of oral contraceptive use and days 15-28. However rectal temperature was higher (P<0.05) and growth hormone tended to be higher (P=0.05) during days 15-28, while plasma glucose was lower (P<0.05). These results demonstrate that for unacclimatised games players the performance of intermittent, high intensity shuttle running in the heat is unaffected by menstrual cycle phase but is influenced by oral contraceptive use

High intensity intermittent running and field hockey skill performance in the heat

Nine well-trained, unacclimatized female hockey players performed the Loughborough Intermittent Shuttle Test (LIST) interspersed with three field hockey skill tests in hot (30°C, 38% relative humidity) and moderate (19°C, 51% relative humidity) environmental conditions. Field hockey skill performance declined in both the hot and moderate conditions following 30 and 60 min of the LIST compared with pre-LIST values (P  < 0.01). This decrement in performance was compounded in the hot environment with a 6% poorer performance in the heat recorded for the second skill test at 30 min (P  < 0.05, hot 101.7 ± 3.6 vs moderate 95.7 ± 2.9 s; mean ± sx). However, no difference was found in the decision-making element of the skill test. Fifteen-metre sprint times were slower in the hot condition (P  < 0.01). In the hot environment, rectal temperature (P < 0.01), perceived exertion (P < 0.05), perceived thirst (P < 0.01), blood glucose concentration (P < 0.05) and serum aldosterone concentration (P < 0.01) were higher. Estimated mean ( ± sx) sweat rate was higher in the hot trial (1.27 ± 0.10 l • h-1) than in the moderate trial (1.05 ± 0.12 l • h-1) (P < 0.05). Body mass was well maintained in both trials. No differences in serum cortisol, blood lactate, plasma volume or plasma ammonia concentrations were found. These results demonstrate that field hockey skill performance is decreased following intermittent high-intensity shuttle running and that this decrease is greater in hot environmental conditions. The exact mechanism for this decrement in performance remains to be elucidated, but is unlikely to be due to low glycogen concentration or dehydration

A heat acclimation protocol for team sports

Background: It is well documented that heat acclimation of 6 or more sessions of at least 60 min duration prolongs the time to exhaustion during endurance walking, cycling and running in the heat. However, this type of acclimation is not specific to team sport activity and the effect of acclimation on prolonged high intensity intermittent running has not yet been investigated. Objective: To assess the impact of an intermittent acclimation protocol on distance run during team sport activity. Methods: The impact of 4 short heat acclimation sessions (30 – 45 min of the Loughborough Intermittent Shuttle Test; LIST) on high-intensity intermittent running capacity (LIST) in the heat (30oC, 27% RH), was examined. Seventeen female welltrained games players were split into 3 groups; an acclimation group (30oC, 24% RH), a moderate training group (18oC, 41% RH), and a control group who did not complete any training between the main trials (pre- and post-acclimation). The pre- (A) and post-acclimation (B) trials were separated by 28 days to control for menstrual phase and verified using hormonal analysis. The 4 acclimation or moderate training sessions utilising the LIST were completed with one or two rest days interspersed between each session in a 10-day period prior to the post-acclimation trial (B). Results: In the post-acclimation trial distance run was increased by 33% in the acclimation group (A: 7703 ± 1401 vs B: 10215 ± 1746m; interaction group x trial P<0.05), but was unchanged in the moderate and control groups. The acclimation group had a lower rectal temperature (interaction group x trial x time P<0.01) due to a lower rate of rise, and an increase in thermal comfort [1] after acclimation (End A: 7 ± 2 vs 6 ± 2; interaction group x trial P<0.01). There was no difference in serum 3 progesterone, aldosterone or cortisol concentrations following acclimation or between groups. Conclusion: Four 30-45 min sessions of intermittent exercise induced acclimation, and resulted in an improvement in intermittent running exercise capacity in female games players. A lower rectal temperature and a concomitant rise in thermal comfort may be partly responsible for the improvement in exercise capacity

The effect of cooling prior to and during exercise on exercise performance and capacity in the heat: a meta-analysis

Exercise is impaired in hot, compared to moderate, conditions. The development of hyperthermia is strongly linked to the impairment and as a result, many different strategies have been investigated to combat this. This meta-analysis focused on one of the most popular strategies: cooling. Pre-cooling has received the most attention but more recently cooling applied during the bout of exercise has also been investigated and both were reviewed. We conducted a literature search and retrieved twenty-eight articles which investigated the effect of cooling administered either prior to (n=23) or during (n=5) an exercise test in hot (WBGT >26°C) conditions. Mean and weighted effect sizes (Cohen’s d) were calculated. Overall, pre-cooling has a moderate (d=0.73) effect on subsequent performance but the magnitude of the effect is dependent upon the nature of the test. Sprint performance is impaired (d=-0.26) but intermittent performance and prolonged exercise are both improved following cooling (d=0.47 and d=1.91 respectively). Cooling during exercise also has a positive effect on performance and capacity (d=0.76). Improvements were observed in studies with and without cooling-induced physiological alterations and the literature supports the suggestion of a dose-response relationship between cooling, thermal strain and improvements in performance and capacity. In summary, pre-cooling can improve subsequent intermittent and prolonged exercise performance and capacity in a hot environment but sprint performance is impaired. Cooling during exercise also has a positive effect on exercise performance and capacity in a hot environment

Half-time and high-speed running in the second half of soccer

This study investigated if the quantity of high-speed running (movements >15 km.h-1) completed in the first 15 minutes of competitive football matches differed from that completed in the corresponding 15 minutes of the second half. Twenty semi-professional soccer players (age 21.2 ± 3.6 years, body mass 76.4 ± 3.8 kg, height 1.89 ± 0.05 m) participated in the study. Fifty competitive soccer matches and 192 data files were analysed (4 ± 2 files per match) using Global Positioning Satellite technology. Data were analysed using 2-way repeated measures ANOVA and Pearson correlations. No differences were found between the first 15 min of each half for the distance completed at high-speed (>15 km.h-1) or sprinting (>21 km.h-1), or in the number of sprints undertaken (p>0.05). However, total distance covered was shorter (1st half vs. 2nd half: 1746 ± 220 vs. 1644 ± 224 m; p<0.001) and mean speed lower (1st half vs. 2nd half: 7.0 ± 0.9 vs. 6.6 ± 0.9 km.h-1; p<0.001) in the first 15 min of the second half compared to the first. The correlations between the duration of the half-time interval and the difference in the high-speed running or sprinting between first and second halves (0-15 min) were very small (r=0.08 [p=0.25] and r=0.04 [p=0.61] respectively). Therefore, this study did not find any difference between the amount of high-speed running and sprinting completed by semi-professional soccer players when the first 15 minutes of the first and second half of competitive matches were compared The maintenance of high-speed running and sprinting, as total distance and mean speed declined, may be a function of the pacing strategies adopted by players in competitive matches

The reliability and validity of a field hockey skill test

High test retest reliability is essential in tests used for both scientific research and to monitor athletic performance. Thirty-nine (20 male and 19 female) well-trained university field hockey players volunteered to participate in the study. The reliability of the in house designed test was determined by repeating the test (3-14 days later) following full familiarisation. The validity was assessed by comparing coaches ranks of players with ranked performance on the skill test. The mean difference and confidence limits in overall skill test performance was 0.0 ± 1.0% and the standard error (confidence limits) was 2.1% (1.7 to 2.8%). The mean difference and confidence limits for the ‘decision making’ time was 0.0 ± 1.0% and the standard error (confidence limits) was 4.5% (3.6 to 6.2%). The validity correlation (Pearson) was r = 0.83 and r= 0.73 for female players and r = 0.61 and r = 0.70 for male players for overall time and ‘decision making’ time respectively. We conclude that the field hockey skill test is a reliable measure of skill performance and that it is valid as a predictor of coach assessed hockey performance, but the validity is greater for female players

Activity profile and between-match variation in elite field hockey

This study aimed to: 1) provide a position specific activity profile for elite male hockey players; 2) determine if the activity profile was altered by the introduction of the ‘self-pass’ rule and 3) provide information relating to match to match variability in elite male field hockey. The activity of 28 elite male field hockey players was analysed over 2 seasons totalling 395 player-match analyses using Global Positioning Satellite technology. Total distance, high speed running (>15.5 km.h-1), sprinting (>20 km.h-1) and mean speed were recorded. Players were categorised into 4 positions: full-back (FB); half-back (HB); midfield (M) and forward (F). Data were analysed using a 2 way ANOVA (season, position) and between-match coefficients of variation (CV). The time played differs with position (FB: 65.5±5.3, HB: 49.5±11.5, M: 45.9±7.1, F: 39.5±5.4 min; P<0.0005) and thus affected the activity profile. Total distance covered was greater for full backs (FB: 8001±447, HB: 6435±1399, M: 6415±908, F: 5844±762 m, p<0.001) and mean speed and percentage time spent high-speed running and sprinting was greater for forwards than all other positions (HSR: FB: 6.8±1.0, HB: 8.8±1.3, M: 10.7±1.2, F: 13.5±1.8 %, p<0.001). The activity profile did not differ with the introduction of the self-pass. Match to match variability (CV) ranged from 5.0% to 22.0% for total and sprint distance respectively. This is the first study to present an activity profile of elite men’s field hockey and its associated variability and demonstrates that each position is unique and therefore training and recovery should be position specific

Sodium bicarbonate supplementation does not improve elite women's team sport running or field hockey skill performance

Team sports, such as field hockey, incorporate high‐intensity repeated sprints, interspersed with low‐intensity running, which can result in acidosis. The aim of the present study was to examine the effect of acute sodium bicarbonate (SB) supplementation on team sport running and skill performance. Eight elite female field hockey players (age 23 ± 5 years, body mass 62.6 ± 8.4 kg, height 1.66 ± 0.05 m) completed three Field Hockey Skill Tests (FHST) interspersed with four sets of the Loughborough Intermittent Shuttle Test (LIST). Prior to exercise, participants were supplemented with capsules equivalent to 0.2 g·kg−1 body mass (BM) of a placebo (maltodextrin) or 0.3 g·kg−1 BM SB. Field hockey skill performance incorporated overall performance time (PFT), movement time (MT), decision‐making time (DMT), and penalty time (PT). Sprint time (ST), rating of perceived exertion (RPE), blood lactate concentration, bicarbonate anion (urn:x-wiley:2051817X:media:phy213818:phy213818-math-0001) concentration, pH, and base excess were measured at various time points. Data (mean ± SD) were analyzed using a two‐way analysis of variance (ANOVA) with repeated measures, with Hedges g effect sizes used to interpret the magnitude of differences. Bicarbonate anion concentration (+5.4 ± 2.6 mmol·L−1) and pH (+0.06 ± 0.03) were greater during the bicarbonate trial compared with the placebo (P 0.30) or ST (placebo: 2.87 ± 0.12 sec; bicarbonate: 2.86 ± 0.12 sec, P = 0.893, g = −0.08). RPE was lower during the SB condition (placebo: 13 ± 2; bicarbonate: 12 ± 2, P = 0.021, g = −0.41). Acute ingestion of bicarbonate did not improve sprint or sport‐specific skill performance. Bicarbonate ingestion did result in a lower perception of effort during team‐sport running, which may have performance implications in a competitive match situation