Wade H. Sinclair

Influence of postexercise cooling techniques on heart rate variability in men.

The reduction of core body temperature (TC) is vitally important in the treatment of hyperthermia; however, little is known regarding the impact of cooling treatments on the autonomic control of heart rate (HR). The aim of the present study was to examine the influence of three field‐based hyperthermia treatments on the neural control of HR via heart rate variability (HRV). Following exercise‐induced hyperthermia (TC∼40.0°C) in a warm environment (34.2 ± 0.5°C), nine healthy, active men were treated during recovery, in a randomized order, with intravenous cold saline infusion (IV) or ice packs (ICE) or fan cooling with intermittent water spray (FAN) for 40 min. During each treatment, HR dynamics via power spectral (VLF, LF, HF), Poincare plot (SD1, SD2), approximate entropy (ApEn) and short‐ (α1) and long‐term (α2) fractal scaling analyses were determined every 10 min. At recovery onset, HR and TC were similar between treatments and were significantly reduced over the 40 min recovery period. During recovery, HR and α2 were significantly reduced from initial levels but were significantly greater for IV compared with ICE and FAN. In contrast, VLF, LF, HF, SD1, SD2 and ApEn increased during recovery, with all being significantly lower for IV compared with ICE and/or FAN. The present results demonstrated that IV, compared with ICE and FAN, resulted in significantly greater HR, reduced spectral and geometrical HRV, lower HR complexity and reduced long‐term HR control, indicative of reduced vagal and/or increased sympathetic modulation. Specific treatments for exercise‐induced hyperthermia may result in an altered sympathovagal balance that requires further examination.

The effects of air travel on performance measures of elite Australian rugby league players

Abstract The current study explored the effects of short haul air travel within the same country on elite Australian rugby league (RL) players (n=12) during two away and two home games of elite competition. Physiological tests of handgrip strength and leg power were assessed along with psychological tests and perceptions of leg soreness and tiredness on the day before the game (Time 1 and Time 2) and on game day (Time 3). Game statistics of tackles and metres gained were assessed for the games analysed. Significant differences were found for daily analyses of life demands for athletes (DALDA) worse than normal responses at Time 2 (2.50±3.23 vs. 3.50±3.93; P=0.04), Karolinska Sleepiness Scale (KSS) at Time 2 (2.88±1.51 vs. 3.71±1.37; P=0.011) and leg tiredness at Time 3 (3.38±1.66 vs. 2.35±1.70; P=0.004) between home and away games. The analysis of game statistics identified that more metres were gained during home games (83.6±49.1 vs. 63.0±30.1; P=0.02) and more tackles made while playing away (18.4±9.2 vs. 14.3±6.7; P=0.016). The results suggest that short haul air travel without crossing time zones results in symptoms of travel fatigue but does not appear to negatively impact on elite RL players ability to perform strength and power tasks. Different game tactics (attacking vs. defensive) occurred between home and away games however, it is unclear whether travel fatigue or a home advantage (HA) is associated with this finding.

Effect of a training week on heart rate variability in elite youth rugby league players.

The aim of this study was to examine the influence of weekly training including a competitive game on heart rate (HR) variability (HRV). Youth players (n=9, age 17-20 years) were monitored during daily supine rest (10 min) and standing (8 min), 5 times over 8 days. Heart rate recordings were analysed for time domain, frequency (e. g. low frequency [LF], high frequency [HF]) domain and non-linear measures of HRV and compared using ANOVA or Friedmans tests. Relationships between HRV and training workloads were examined via Spearman rank rho (ρ) correlation coefficients. Prior to a game, mean HR was significantly increased and remained elevated until 2 days post-game while parasympathetic modulations (HF) were significantly reduced (p<0.05). The supine to standing change in HRV was significantly reduced for up to 4 days post-game (LF/HF ratio, - 1.0±2.9 vs. - 3.0±1.9, p<0.05). These results confirm that prior to a game, players exhibited reduced parasympathetic and/or predominant sympathetic modulation with the game significantly reducing autonomic responses to standing for up to the following 4 days. Identification of day to day fluctuations in HRV may provide a helpful tool for monitoring player workload to maximise training and game performance.

Comparison of physiological responses to graded exercise test performance in outrigger canoeing

Abstract The aim of this study was to establish a graded exercise test protocol for determining the peak physiological responses of female outrigger canoeists. Seventeen trained female outrigger canoeists completed two outrigger ergometer graded exercise test protocols in random order: (1) 25 W power output for 2 min increasing by 7.5 W every minute until exhaustion; and (2) 25 W power output for 2 min increasing by 15 W every 2 min to exhaustion. Heart rate and power output were recorded every 15 s. Expired air was collected continuously and sampled for analysis at 15-s intervals, while blood lactate concentration was measured immediately after and 3, 5, and 7 min after exercise. The peak physiological and performance variables examined included peak oxygen uptake ([Vdot]O2peak), minute ventilation, tidal volume, ventilatory thresholds 1 and 2, respiratory rate, respiratory exchange ratio, heart rate, blood lactate concentration, power output, performance time, and time to [Vdot]O2peak. There were no significant differences in peak physiological responses, ventilatory thresholds or performance variables between the two graded exercise test protocols. Despite no significant differences between protocols, due to the large limits of agreement evident between protocols for the peak physiological responses, it is recommended that the same protocol be used for all comparison testing to minimize intra-individual variability of results.

Wearing long pants while working outdoors in the tropics does not yield higher body temperatures

Objective: To compare the thermoregulatory demands of outdoor workers wearing long or knee‐length pants while working in situ in a tropical environment.

Identification and reliability of pacing strategies in outrigger canoeing ergometry

This study examined the pacing strategies utilised; and the performance reproducibility during repeated outrigger canoeing ergometer time trials. Trained female outrigger canoeists (N=11) completed four 1000m outrigger canoe ergometer time trials. There was a significant 1.5% improvement in 1000m time in trial four compared to trial one. A fast start strategy was adopted in 36 of the 44 trials (82%) followed by a deceleration during the mid stages. As trials progressed there was an increased adoption of negative pacing (fast finish) between the last two splits, indicating a learning effect of pacing strategy across repeated trials. These results demonstrate that although some performance improvement was evident between the first and fourth time trials, the 1000m outrigger ergometer time trial is a reliable test that may be used as a tool to assist with crew selection and performance monitoring. Further, on account of the variation in pacing strategy noted in the fourth trial, the authors recommend utilising one familiarisation session and one test session when assessing performance such that learning or training adaptations resulting from multiple trials do not impact on results.

The Reliability of VO2peak Determination in Healthy Females during an Incremental Arm Ergometry Test

This study examined the reliability of an incremental arm ergometry (AE) protocol during peak aerobic power (VO2(peak)) determination in healthy females. Fifteen females completed two incremental AE tests to exhaustion, seven to eleven days apart, using a mechanically braked arm ergometer. The initial work rate was 16W and increased by 16W every two minutes until exhaustion. Significant differences between tests were determined by repeated measures ANOVA, and paired t-tests or Wilcoxon signed-rank tests, where appropriate. Reliability was determined by intraclass correlation coefficients (ICC), typical error, coefficient of variation (CV) and measurement bias/ratio and 95% limits of agreement (LOA). Peak cardio-respiratory responses were similar between tests, except for tidal volume (1.95 +/-0.47 vs. 1.81 +/- 0.41 L, P<0.05). Reliability for peak variables was moderate to high (ICC=0.659-0.941; CV< or =10%) while LOA were considerable for most variables including VO2(peak) (LOA=0.57 L.min(-1)). Similar peak cardio-respiratory responses, low CV and moderate-high ICC confirmed the reliability of the current incremental AE protocol to be similar to that of prior reported protocols for VO2(peak) determination. Substantial within-participant variability (LOA) for respiratory rate and tidal volume was common during the AE protocol and possibly reflects the influence of respiratory entrainment on reliability that requires further investigation.

Predictors of 1000-m Outrigger Canoeing Performance

UNLABELLED This study examined the relationships between body composition, peak oxygen consumption and 1000-m time trial performance of female outrigger canoeists. PROCEDURES Female outrigger canoeists (n = 17) completed anthropometric profiling and a 1000-m outrigger ergometer time trial, during which expired air was measured continuously and analysed at 15-s intervals for determination of peak oxygen consumption. Heart rate, stroke rate and power output were also recorded at 15-s intervals. Blood lactate was measured immediately and at 3-, 5- and 7-min post-exercise. Mean power output, peak power output and progressive split times were highly correlated (r > 0.80) to 1000-m performance. Arm girths, humerus breadth, mesomorphy, peak oxygen consumption, ventilation, mean heart rate and peak lactate were moderately correlated (r > 0.50) to 1000-m performance. Stepwise multiple regression analysis verified that mean power output and to a lesser extent flexed arm girth, humerus breadth, waist girth and sitting height can predict 1000-m performance. Enhanced 1000-m performance of female outrigger canoeists appears to be achieved through a combination of greater power production and maintenance, a muscular stature and to a lesser extent, a higher aerobic capacity. These characteristics should be considered when selecting crews.

Influence of Cycle Ergometer Type and Sex on Assessment of 30-Second Anaerobic Capacity and Power

This study examined the influence of cycle ergometer type and sex on assessment of 30-s anaerobic capacity and power. 41 healthy adults performed a 30-s anaerobic cycle test using a mechanically- (ME) and air-braked (AE) ergometer in a randomised order, approximately 7 days apart. Peak heart rate (HR) and rating of perceived exertion were similar between tests with peak HR greater for females compared to males (187.0 ± 9.1 vs. 180.8 ± 9.9 bpm, p<0.05). Peak power (1 100 ± 330 vs. 802 ± 225 W), mean power (793 ± 223 vs. 587 ± 156 W) and total work (23.8 ± 6.7 vs. 17.6 ± 4.7 kJ) were greater for AE compared to ME (p<0.001) and greater for males compared to females (p<0.001). The mean difference for anaerobic capacity and power between AE and ME were similar for males and females (37-41% vs. 33-35%, p>0.05). Peak lactate was greater for AE compared to ME (16.1 ± 3.4 vs. 14.8 ± 2.9 mmol·L (-1); p<0.05) and greater for males compared to females (16.2 ± 3.5 vs. 14.6 ± 2.7 mmol·L (-1); p<0.05). The current study demonstrated that anaerobic power and capacity were substantially greater when assessed using AE compared to the traditional ME with the difference between ergometer types unaffected by sex. Ergometer type should be considered when comparing anaerobic results across populations and/or studies.

Reliability of two metabolic systems during sport-specific upper-body ergometry

Abstract In this study, we assessed the reliability of the portable Cosmed K4b2 and the laboratory-based Powerlab 8M gas analysis systems for measuring peak physiological variables during sport-specific upper-body exercise, to determine the error associated with repeated physiological performance tests. Ten trained female outrigger canoeists completed two 1000-m ergometer time trials using each gas analysis system. Peak physiological responses were analysed using a two-way repeated-measures analysis of variance and post hoc Tukey HSD tests. Reliability and within-participant variability of peak responses were assessed using intraclass correlation coefficients (ICC) and measurement bias/ratios with 95% limits of agreement (LOA), respectively. Performance and peak physiological responses were similar across trials for each individual system, although the Powerlab 8M reported significantly higher (13.6%) carbon dioxide production (VCO2) and non-significantly higher (7.4%) oxygen consumption (VO2) than the Cosmed K4b2. Reliability of the Cosmed K4b2 was high for VCO2 (0.98) and moderate for ventilation (0.85), whereas that for the Powerlab 8M was high for VCO2 (0.97) and tidal volume (0.94) and moderate for VO2 (0.87). Overall, the two systems report similar VO2 variability (8–9%) with the Powerlab 8M reporting higher VO2 and VCO2 values than the Cosmed K4b2. Therefore, while each system is reliable, results from each of the systems should not be used interchangeably.