Comparing Maximal Mean and Critical Speed and Metabolic Powers in Elite and Sub-elite Soccer

The quantification of maximal mean speed (MMS), maximal mean metabolic power (MMP_met), critical speed (CS) and critical metabolic power (CP_met) was conducted over full A-League (elite) and National Premier League (NPL; sub-elite) seasons. Comparisons were made between levels of soccer competition and playing positions (i. e. centre backs, full backs, central midfielders, wide midfielders and strikers). A symmetric moving average algorithm was applied to the GPS raw data using specific time windows (i. e. 1, 5, 10, 60, 300 and 600 s) and maximal values were obtained. Additionally, these maximal values were used to derive estimates of CS and CP_met. Maximal mean values, particularly during smaller time windows (i. e. 1 and 5 s), were greater in A-League match play. Only MMP_met1 was identified as being consistently different between competitions (P=<0.001-0.049) in all playing positions. Significance was only observed in CS (P=0.005) and CP_met (P=0.005) of centre backs between competitions. Centre backs were identified as the least energy demanding playing position. The present findings suggests that both maximal mean and critical analyses are suitable alternatives to common absolute distance and speed assessments of match running performance during competitive matches.

A Reduction in Match-to-match Variability Using Maximal Mean Analyses in Sub-elite Soccer

The match-to-match variability of external loads in National Premier League soccer competition was determined. Global positioning systems (GPS) data were collected from 20 sub-elite soccer players over 2-10 matches from a single season. Match data were collected from during one season. Twenty-six matches were recorded and 10 were utilised within final match-to-match analysis based on stringent data selection criteria. A symmetric moving average algorithm was applied to GPS data over specific time windows (1, 5, 10, 60, 300 and 600 s), and maximal speed and metabolic power values then calculated at each time interval during each match. Match-to-match coefficients of variation (CV) were greatest for sprint-speed running distance (36.3-43.6%) when comparing 2 vs. 10 matches. CVs for maximal mean speed (4.9-7.0%) and metabolic power (4.4-9.6%) ranged from good to moderate. As the variability of absolute high-speed distance values are greater, and therefore less reliable, their use as indicators of performance is reduced, suggesting that maximal mean analyses could be used as an alternative in the assessment of match running performance during competitive matches.

Skeletal Muscle Microvascular Adaptations Following Regular Cold Water Immersion

This study investigated the effect of endurance training and regular post-exercise cold water immersion on changes in microvascular function. Nine males performed 3 sessions∙wk-1 of endurance training for 4 weeks. Following each session, participants immersed one leg in a cold water bath (10°C; COLD) for 15 min while the contra-lateral leg served as control (CON). Before and after training, microvascular function of the gastrocnemius was assessed using near-infrared spectroscopy, where 5 min of popliteal artery occlusion was applied and monitored for 3 min upon cuff release. Changes in Hbdiff (oxyhemoglobin - deoxyhemoglobin) amplitude (O-AMP), area under curve (O-AUC) and estimated muscle oxygen consumption (mVO₂) were determined during occlusion, while the reperfusion rate (R-RATE), reperfusion amplitude (R-AMP) and hyperemic response (HYP) were determined following cuff release. Training increased O-AMP (p=0.010), O-AUC (p=0.011), mVO₂ (p=0.013), R-AMP (p=0.004) and HYP (p=0.057). Significant time (p=0.024) and condition (p=0.026) effects were observed for R-RATE, where the increase in COLD was greater compared with CON (p=0.026). In conclusion, R-RATE following training was significantly higher in COLD compared with CON, providing some evidence for enhanced microvascular adaptations following regular cold water immersion.

Live high, train low - influence on resting and post-exercise hepcidin levels

The post-exercise hepcidin response during prolonged (>2 weeks) hypoxic exposure is not well understood. We compared plasma hepcidin levels 3 h after exercise [6 × 1000 m at 90% of maximal aerobic running velocity (vVO_2max )] performed in normoxia and normobaric hypoxia (3000 m simulate altitude) 1 week before, and during 14 days of normobaric hypoxia [196.2 ± 25.6 h (median: 200.8 h; range: 154.3-234.8 h) at 3000 m simulated altitude] in 10 well-trained distance runners (six males, four females). Venous blood was also analyzed for hepcidin after 2 days of normobaric hypoxia. Hemoglobin mass (Hb_mass ) was measured via CO rebreathing 1 week before and after 14 days of hypoxia. Hepcidin was suppressed after 2 (Cohen's d = -2.3, 95% confidence interval: [-2.9, -1.6]) and 14 days of normobaric hypoxia (d = -1.6 [-2.6, -0.6]). Hepcidin increased from baseline, 3 h post-exercise in normoxia (d = 0.8 [0.2, 1.3]) and hypoxia (d = 0.6 [0.3, 1.0]), both before and after exposure (normoxia: d = 0.7 [0.3, 1.2]; hypoxia: d = 1.3 [0.4, 2.3]). In conclusion, 2 weeks of normobaric hypoxia suppressed resting hepcidin levels, but did not alter the post-exercise response in either normoxia or hypoxia, compared with the pre-exposure response.

Physical Demands of Sprinting in Professional Road Cycling

The aim of this study was to quantify the demands of road competitions ending with sprints in male professional cycling. 17 races finished with top-5 results from 6 male road professional cyclists (age, 27.0±3.8 years; height, 1.76±0.03 m; weight, 71.7±1.1 kg) were analysed. SRM power meters were used to monitor power output, cadence and speed. Data were averaged over the entire race, different durations prior to the sprint (60, 10, 5 and 1 min) and during the actual sprint. Variations in power during the final 10 min of the race were quantified using exposure variation analysis. This observational study was conducted in the field to maximize the ecological validity of the results. Power, cadence and speed were statistically different between various phases of the race (p<0.001), increasing from 316±43 W, 95±4 rpm and 50.5±3.3 km·h(-1) in the last 10 min, to 487±58 W, 102±6 rpm and 55.4±4.7 km·h(-1) in the last min prior to the sprint. Peak power during the sprint was 17.4±1.7 W·kg(-1). Exposure variation analysis revealed a significantly greater number of short-duration high-intensity efforts in the final 5 min of the race, compared with the penultimate 5 min (p=0.010). These findings quantify the power output requirements associated with high-level sprinting in men's professional road cycling and highlight the need for both aerobic and anaerobic fitness.

Pacing, the missing piece of the puzzle to high-intensity interval training

This study examined physiological and perceptual responses to matched work high-intensity interval training using all-out and 2 even-paced methodologies. 15 trained male cyclists performed 3 interval sessions of three 3-min efforts with 3 min of active recovery between efforts. The initial interval session was completed using all-out pacing, with the following 2 sessions being completed with computer- and athlete-controlled pacing in a randomised and semi-counterbalanced manner. Computer- and athlete-controlled intervals were completed at the mean power from the corresponding interval during the all-out trial. Oxygen consumption and ratings of perceived exertion were recorded during each effort. 20 min following each session, participants completed a 4-km time trial and provided sessional rating of perceived exertion. Oxygen consumption was greater during all-out (54.1±6.6 ml.kg(-1).min(-1); p<0.01) and athlete-controlled (53.0±5.8 ml.kg(-1).min(-1); p<0.01) compared with computer-controlled (51.5±5.7 ml.kg(-1).min(-1)). Total time ≥85% maximal oxygen consumption was greater during all-out compared to both even-paced efforts. Sessional ratings of perceived exertion were greater after all-out compared to both even-paced sessions. Mean 4-km power output was lower after all-out compared with both even paced intervals. Distribution of pace throughout high-intensity interval training can influence perceptual and metabolic stress along with subsequent performance and should be considered during the prescription of such training.

Influence of all-out and fast start on 5-min cycling time trial performance

PURPOSE

To examine the influence of two different fast-start pacing strategies on performance and oxygen consumption (VO2) during cycle ergometer time trials lasting ∼5 min.

METHODS

Eight trained male cyclists performed four cycle ergometer time trials whereby the total work completed (113 ± 11.5 kJ; mean ± SD) was identical to the better of two 5-min self-paced familiarization trials. During the performance trials, initial power output was manipulated to induce either an all-out or a fast start. Power output during the first 60 s of the fast-start trial was maintained at 471.0 ± 48.0 W, whereas the all-out start approximated a maximal starting effort for the first 15 s (mean power: 753.6 ± 76.5 W) followed by 45 s at a constant power output (376.8 ± 38.5 W). Irrespective of starting strategy, power output was controlled so that participants would complete the first quarter of the trial (28.3 ± 2.9 kJ) in 60 s. Participants performed two trials using each condition, with their fastest time trial compared.

RESULTS

Performance time was significantly faster when cyclists adopted the all-out start (4 min 48 s ± 8 s) compared with the fast start (4 min 51 s ± 8 s; P < 0.05). The first-quarter VO2 during the all-out start trial (3.4 ± 0.4 L·min(-1)) was significantly higher than during the fast-start trial (3.1 ± 0.4 L·min(-1); P < 0.05). After removal of an outlier, the percentage increase in first-quarter VO2 was significantly correlated (r = -0.86, P < 0.05) with the relative difference in finishing time.

CONCLUSIONS

An all-out start produces superior middle distance cycling performance when compared with a fast start. The improvement in performance may be due to a faster VO2 response rather than time saved due to a rapid acceleration.

Pack hike test finishing time for Australian firefighters: pass rates and correlates of performance

The pack hike test (PHT, 4.83 km hike wearing a 20.4-kg load) was devised to determine the job readiness of USA wildland firefighters. This study measured PHT performance in a sample of Australian firefighters who currently perform the PHT (career land management firefighters, LMFF) and those who do not (suburban/regional volunteer firefighters, VFF). The study also investigated the relationships between firefighters' PHT performance and their performance across a range of fitness tests for both groups. Twenty LMFF and eighteen age-, body mass-, and height-matched VFF attempted the PHT, and a series of muscular endurance, power, strength and cardiorespiratory fitness tests. Bivariate correlations between the participants' PHT finishing time and their performance in a suite of different fitness tests were determined using Pearson's product moment correlation coefficient. The mean PHT finishing time for LMFF (42.2 ± 2.8 min) was 9 ± 14% faster (p = 0.001) than for VFF (46.1 ± 3.6 min). The pass rate (the percentage of participants who completed the PHT in under 45 min) for LMFF (90%) was greater than that of VFF (39%, p = 0.001). For LMFF, VO(2peak) in L min(-1)(r = -0.66, p = 0.001) and the duration they could sustain a grip 'force' of 25 kg (r = -0.69, p = 0.001) were strongly correlated with PHT finishing time. For VFF, VO(2peak) in mL kg(-1) min(-1)(r = -0.75, p = 0.002) and the duration they could hold a 1.2-m bar attached to 45.5 kg in a 'hose spray position' (r = -0.69, p = 0.004) were strongly correlated with PHT finishing time. This study shows that PHT fitness-screening could severely limit the number of VFF eligible for duty, compromising workforce numbers and highlights the need for specific and valid firefighter fitness standards. The results also demonstrate the strong relationships between PHT performance and firefighters' cardiorespiratory fitness and local muscular endurance. Those preparing for the PHT should focus their training on these fitness components in the weeks and months prior to undertaking the PHT.

Muscle deoxygenation during repeated sprint running: Effect of active vs. passive recovery

The purpose of this study was to compare the effect of active (AR) versus passive recovery (PR) on muscle deoxygenation during short repeated maximal running. Ten male team sport athletes (26.9+/-3.7y) performed 6 repeated maximal 4-s sprints interspersed with 21 s of either AR (2 m.s (-1)) or PR (standing) on a non-motorized treadmill. Mean running speed (AvSp (mean)), percentage speed decrement (Sp%Dec), oxygen uptake (V O (2)), deoxyhemoglobin (HHb) and blood lactate ([La] (b)) were computed for each recovery condition. Compared to PR, AvSp (mean) was lower (3.79+/-0.28 vs. 4.09+/-0.32m.s (-1); P<0.001) and Sp%Dec higher (7.2+/-3.7 vs. 3.2+/-0.1.3%; P<0.001) for AR. Mean V O (2) (3.64+/-0.44 vs. 2.91+/-0.47L.min (-1), P<0.001), HHb (94.4+/-16.8 vs. 83.4+/-4.8% of HHb during the first sprint, P=0.02) and [La] (b) (13.5+/-2.5 vs. 12.7+/-2.2 mmol.l (-1), P=0.03) were significantly higher during AR compared to PR. In conclusion, during run-based repeated sprinting, AR was associated with reduced repeated sprint ability and higher muscle deoxygenation.

Influence of starting strategy on cycling time trial performance in the heat

The purpose of this study was to determine the influence of starting strategy on time trial performance in the heat. Eleven endurance trained male cyclists (30+/-5 years, 79.5+/-4.6 kg, VO(2max) 58.5+/-5.0 ml x kg x (-1) min(-1)) performed four 20-km time trials in the heat (32.7+/-0.7 degrees C and 55% relative humidity). The first time trial was completed at a self-selected pace (SPTT). During the following time trials, subjects performed the initial 2.5-km at power outputs 10% above (10% ATT), 10% below (10% BTT) or equal (ETT) to that of the average power during the initial 2.5-km of the self-selected trial; the remaining 17.5-km was self-paced. Throughout each time trial, power output, rectal temperature, skin temperature, heat storage, pain intensity and thermal sensation were taken. Despite significantly (P<0.05) greater power outputs for 10% BTT (273+/-45W) compared with the ETT (267+/-48W) and 10% ATT (265+/-41W) during the final 17.5-km, overall 20-km performance time was not significantly different amongst trials. There were no differences in any of the other measured variables between trials. These data show that varying starting power by +/-10% did not affect 20 km time trial performance in the heat.

Effect of cold water immersion on postexercise parasympathetic reactivation

The aim of the present study was to assess the effect of cold water immersion (CWI) on postexercise parasympathetic reactivation. Ten male cyclists (age, 29 +/- 6 yr) performed two repeated supramaximal cycling exercises (SE(1) and SE(2)) interspersed with a 20-min passive recovery period, during which they were randomly assigned to either 5 min of CWI in 14 degrees C or a control (N) condition where they sat in an environmental chamber (35.0 +/- 0.3 degrees C and 40.0 +/- 3.0% relative humidity). Rectal temperature (T(re)) and beat-to-beat heart rate (HR) were recorded continuously. The time constant of HR recovery (HRRtau) and a time (30-s) varying vagal-related HR variability (HRV) index (rMSSD(30s)) were assessed during the 6-min period immediately following exercise. Resting vagal-related HRV indexes were calculated during 3-min periods 2 min before and 3 min after SE(1) and SE(2). Results showed no effect of CWI on T(re) (P = 0.29), SE performance (P = 0.76), and HRRtau (P = 0.61). In contrast, all vagal-related HRV indexes were decreased after SE(1) (P < 0.001) and tended to decrease even further after SE(2) under N condition but not with CWI. When compared with the N condition, CWI increased HRV indexes before (P < 0.05) and rMSSD(30s) after (P < 0.05) SE(2). Our study shows that CWI can significantly restore the impaired vagal-related HRV indexes observed after supramaximal exercise. CWI may serve as a simple and effective means to accelerate parasympathetic reactivation during the immediate period following supramaximal exercise.

Effect of a 5-min cold-water immersion recovery on exercise performance in the heat

BACKGROUND

This study examined the effect of a 5-min cold-water immersion (14 degrees C) recovery intervention on repeated cycling performance in the heat.

METHODS

10 male cyclists performed two bouts of a 25-min constant-paced (254 (22) W) cycling session followed by a 4-km time trial in hot conditions (35 degrees C, 40% relative humidity). The two bouts were separated by either 15 min of seated recovery in the heat (control) or the same condition with 5-min cold-water immersion (5th-10th minute), using a counterbalanced cross-over design (CP(1)TT(1) --> CWI or CON --> CP(2)TT(2)). Rectal temperature was measured immediately before and after both the constant-paced sessions and 4-km timed trials. Cycling economy and Vo(2) were measured during the constant-paced sessions, and the average power output and completion times were recorded for each time trial.

RESULTS

Compared with control, rectal temperature was significantly lower (0.5 (0.4) degrees C) in cold-water immersion before CP(2) until the end of the second 4-km timed trial. However, the increase in rectal temperature (0.5 (0.2) degrees C) during CP(2) was not significantly different between conditions. During the second 4-km timed trial, power output was significantly greater in cold-water immersion (327.9 (55.7) W) compared with control (288.0 (58.8) W), leading to a faster completion time in cold-water immersion (6.1 (0.3) min) compared with control (6.4 (0.5) min). Economy and Vo(2) were not influenced by the cold-water immersion recovery intervention.

CONCLUSION

5-min cold-water immersion recovery significantly lowered rectal temperature and maintained endurance performance during subsequent high-intensity exercise. These data indicate that repeated exercise performance in heat may be improved when a short period of cold-water immersion is applied during the recovery period.

Core temperature and hydration status during an Ironman triathlon

BACKGROUND

Numerous laboratory based studies have documented that aggressive hydration strategies (approximately 1-2 litres/h) are required to minimise a rise in core temperature and minimise the deleterious effects of hyperthermia on performance. However, field data on the relations between hydration level, core body temperature, and performance are rare.

OBJECTIVE

To measure core temperature (Tcore) in triathletes during a 226 km Ironman triathlon, and to compare Tcore with markers of hydration status after the event.

METHOD

Before and immediately after the 2004 Ironman Western Australia event (mean (SD) ambient temperature 23.3 (1.9) degrees C (range 19-26 degrees C) and 60 (14)% relative humidity (44-87%)) body mass, plasma concentrations of sodium ([Na+]), potassium ([K+]), and chloride ([Cl-]), and urine specific gravity were measured in 10 well trained triathletes. Tcore was measured intermittently during the event using an ingestible pill telemetry system, and heart rate was measured throughout.

RESULTS

Mean (SD) performance time in the Ironman triathlon was 611 (49) minutes; heart rate was 143 (9) beats/min (83 (6)% of maximum) and Tcore was 38.1 (0.3) degrees C. Body mass significantly declined during the race by 2.3 (1.2) kg (-3.0 (1.5)%; p < 0.05), whereas urine specific gravity significantly increased (1.011 (0.005) to 1.0170 (0.008) g/ml; p < 0.05) and plasma [Na+], [K+], and [Cl-] did not change. Changes in body mass were not related to finishing Tcore (r = -0.16), plasma [Na+] (r = 0.31), or urine specific gravity (r = -0.37).

CONCLUSION

In contrast with previous laboratory based studies examining the influence of hypohydration on performance, a body mass loss of up to 3% was found to be tolerated by well trained triathletes during an Ironman competition in warm conditions without any evidence of thermoregulatory failure.