Exposure to a combination of heat and hyperoxia during cycling at submaximal intensity does not alter thermoregulatory responses

In this study, we tested the hypothesis that breathing hyperoxic air (F_inO₂ = 0.40) while exercising in a hot environment exerts negative effects on the total tissue level of haemoglobin concentration (tHb); core (T_core) and skin (T_skin) temperatures; muscle activity; heart rate; blood concentration of lactate; pH; partial pressure of oxygen (P_aO₂) and carbon dioxide; arterial oxygen saturation (S_aO₂); and perceptual responses. Ten well-trained male athletes cycled at submaximal intensity at 21°C or 33°C in randomized order: first for 20 min while breathing normal air (F_inO₂ = 0.21) and then 10 min with F_inO₂ = 0.40 (HOX). At both temperatures, S_aO₂ and P_aO₂, but not tHb, were increased by HOX. Tskin and perception of exertion and thermal discomfort were higher at 33°C than 21°C (p < 0.01), but independent of F_inO₂. T_core and muscle activity were the same under all conditions (p > 0.07). Blood lactate and heart rate were higher at 33°C than 21°C. In conclusion, during 30 min of submaximal cycling at 21°C or 33°C, T_core, T_skin and T_body, tHb, muscle activity and ratings of perceived exertion and thermal discomfort were the same under normoxic and hyperoxic conditions. Accordingly, breathing hyperoxic air (F_inO₂ = 0.40) did not affect thermoregulation under these conditions.

Relationship between core strength and key variables of performance in elite rink hockey players

AIM

The aim of this study was to test the hypothesis that a significant relationship exists between the level of core strength-endurance and key variables of endurance, strength, power, speed, and agility performance in male elite rink hockey players.

METHODS

Ten male elite rink hockey players of the German national team were tested for 1) time to exhaustion, maximum oxygen uptake, and running economy, 2) one repetition maximum bench press and half squat, 3) counter movement jump height, 4) 5 m, 10 m, and 20 m speed, and 5) 22 m agility. The rink hockey players were also tested for 6) ventral, lateral-left, lateral-right, and dorsal core strength-endurance using concentric-eccentric muscle tests.

RESULTS

The level of total and ventral core strength-endurance was very largely correlated with maximum oxygen uptake (r=0.74 and r=0.71, both P<0.05). Additionally, there was a large correlation between the level of ventral core strength-endurance and time to exhaustion (r=0.66, P<0.05). No further significant relationships were observed (best r=0.60, P>0.05).

CONCLUSION

The findings from this study suggest that the level of core strength-endurance is largely to very largely correlated with key variables of endurance performance, but not significantly with strength, power, speed, or agility indicators in male elite rink hockey players. These findings should be noted by coaches and scientists when testing physical fitness or planning strength and conditioning programs for male elite rink hockey players.

[Reliability of Selected Parameters of Cycling Ergospirometry from the PowerCube-Ergo Respiratory Gas Analyser]

This study aimed to investigate the reliability of 1) the key parameters of cycling ergospirometry (maximum power output [Pmax] and oxygen uptake [V̇O2peak], ventilatory thresholds 1 [VT 1] and 2 [VT 2], and cycling efficiency [CE] and gross efficiency [GE]), 2) the commonly used parameters to quantify exhaustion (maximum heart rate [HFmax], respiratory quotient [RQmax], blood lactate concentration [BLAmax], and ratings of perceived exhaustion [RPEmax]), and 3) the kinetics of exercise induced gas exchange measurements (oxygen uptake [V̇O2], carbon dioxide output [V̇CO2], and minute ventilation [V̇E]) using the PowerCube-Ergo metabolic system in consideration of international statistical recommendations. 12 women and 12 men (28 ± 4 years; 23.2 ± 2.4 kg/m(2)) performed two cycling tests (20 watt/min) separated by one week. The reliability was calculated based on differences in means (t test and effect sizes), retest correlation (intraclass correlation coefficient [ICC]), and within-subject variation (standard error of measurement [SEM]). Of the key parameters of cycling ergospirometry, an excellent reliability (ICC ≥ 0.969; p = 0.000) and high accuracy (%SEM ≤ 4.6) were found for Pmax, V̇O2peak, and VT 1. Of the most commonly used parameters to quantify exhaustion, an excellent reliability (ICC = 0.922; p = 0.000) and high accuracy (%SEM = 1.0) existed only for HFmax. The gas exchange measurements (V̇O2, V̇CO2 und V̇E) of the PowerCube-Ergo were all excellently reliable (ICC ≥ 0,991; p = 0.000) and the accuracy of V̇O2 (SEM = 0.10 l/min) and V̇E (SEM = 3.13 l/min) fulfilled the quality guidance of exercise physiology laboratories. For future studies and practical purposes, the results are vital for the decision as to whether a difference between two tests represents a true intervention effect or just a measurement error and for the estimation of required sample sizes.

How accurate are Omron X-HJ-304-E and Yamax SW-700/701 pedometers at different speeds and various inclinations?

AIM

The purpose of this study was to investigate step count and energy expenditure accuracy of the piezoelectric Omron (Walking Style X-HJ-304-E) and spring-levered Yamax (Digi-Walker-SW-700/701) pedometers at different speeds and various inclinations.

METHODS

Thirty subjects (15 females, aged: 24 ± 3 years) completed eleven 5-min trials at different treadmill speeds and inclinations (3.24 km∙h⁻¹ [inclination: 0, 9, 20%], 4.68 km∙h⁻¹ [0, 9, 20%], 6.48 km∙h⁻¹ [0, 9%], 9 km∙h⁻¹ [0%], 10.8 km∙h⁻¹ [0%], 12.6 km∙h⁻¹ [0%]). During each trial, an investigator recorded actual steps with a hand tally counter. Actual energy expenditure was measured using a portable indirect calorimeter.

RESULTS

The Omron pedometer revealed high step count accuracy for all speeds and inclinations when worn on the hip or a backpack (Mean % of actual steps: 99.6%; Range: 95.8-101.3%). The Yamax pedometer revealed high step count accuracy (Mean % of actual steps: 99.8%; Range: 96.2-103.3%) when worn on the left hip at 6.48-12.6 km∙h⁻¹ (0%), 4.68 km∙h⁻¹ (9%, 20%), 6.48 km∙h⁻¹ (9%) and on the right hip at 10.8 km∙h⁻¹ (0%) and 6.48 km∙h⁻¹ (9%). The accuracy of the Omron and Yamax determined energy expenditure was poor (57.9-59.7%) when compared to indirect calorimetry.

CONCLUSION

The Omron pedometer provides accurate step counts when worn on the hip and backpack at all tested speeds and inclinations. We therefore suggest an accurate application of this device for walking, hiking and running at moderate speeds. Both pedometers underestimated energy expenditure.

Cardiorespiratory, metabolic and hormonal responses during open-wheel indoor kart racing

AIM

This study aimed to quantify the cardiorespiratory, metabolic and hormonal responses of elite open-wheel indoor kart racers.

METHODS

Ten male racers (age: 21±3 yrs; height: 1.92±0.06 m, body mass: 76.0±5.9 kg) participated in a racing tournament. Their peak oxygen uptake and heart rate were assessed by a ramp test (100 W, increase 30 W·min-1) in the laboratory. During the racing itself, the cardio-respiratory and accelerometer values were recorded and pre- and post-race levels of blood lactate and salivary cortisol were determined.

RESULTS

The average peak values for all of the drivers with respect to oxygen uptake and heart rate were 4.5±0.8 L·min-1 (56.7±7.9 mL·min-1·kg-1) and 193±5 beats·min-1, respectively. Overall, 28.3±3.3 laps were completed during 30-min of racing. Acceleration forces for the entire test averaged 1.20±0.51 G (maximum: 3.30 G), declining from the first 10 min until the end of racing (P<0.03). The oxygen uptake (~20 mL·min-1·kg-1), heart rate (~133 beats·min-1), respiratory exchange ratio (~0.96) and ventilation (~70 L·min-1) observed indicated moderate cardio-respiratory responses. Blood lactate concentration was significantly higher after the race than before but remained at <2 mmol·L-1 (P<0.01; effect size: 1.62).

CONCLUSION

There were no differences between salivary cortisol levels before and after the race (P<0.06; effect size: 0.49). Directly after the race, the drivers rated their perceived exertion on Borg's scale as 11.1±1.3. The present data revealed that the psycho-physical exertion associated with a 30-min open-wheel indoor kart race is moderate.

[Adaptive mechanisms and behavioural recommendations: playing football in heat, cold and high altitude conditions]

Football is played worldwide and players often have to cope with hot and cold temperatures as well as high altitude conditions. The upcoming and past world championships in Brazil, Qatar and South Africa illustrate the necessity for behavioural strategies and adaptation to extreme environmental conditions. When playing football in the heat or cold, special clothing, hydration and nutritional and acclimatisation strategies are vital for high-level performance. When playing at high altitude, the reduced oxygen partial pressure impairs endurance performance and alters the technical and tactical requirements. Special high-altitude adaptation and preparation strategies are essential for football teams based at sea-level in order to perform well and compete successfully. Therefore, the aim of the underlying review is: 1) to highlight the difficulties and needs of football teams competing in extreme environmental conditions, 2) to summarise the thermoregulatory, physiological, neuronal and psychological mechanism, and 3) to provide recommendations for coping with extreme environmental conditions in order to perform at a high level when playing football in the heat, cold and at high altitude.

[Effects of compression textiles on performance enhancement and recovery]

INTRODUCTION

In competitive sports different types of compression garments (socks, shorts, tights and whole body suits) have become popular. The results of scientific studies regarding their effectiveness, however, are heterogeneous. The aim of this literature review is to (i) survey the scientific data regarding performance enhancing benefits and the support of recovery when applying compression fabrics and (ii) to describe the practical relevance for the application of compression textiles in the competitive sport context.

METHOD

In order to detect relevant publications for the present review an internet search using the medical databases "Medline" and "PubMed" was performed. Altogether, 37 studies were analysed. All publications were from the years 1987 to 2010.

RESULTS

The literature review showed no general scientific indications regarding the benefit of compression garments in competitive sports.

CONCLUSION

In particular, the different study designs and different clothing styles as well as different pressure gradients gave rise to contradictory data.

Physiological effects of a new racing suit for elite cross country skiers

AIM

The aim of this paper was to investigate the influence of the new cross country racing suit, designed for the Olympic Winter Games in Vancouver 2010, on cardio-respiratory, thermoregulatory and perceptual responses.

METHODS

Six elite cross country skiers (29±6 years, peak oxygen uptake 73.2±6.9 mL·min-1·kg-1) performed two exercise bouts wearing either the 2009 or the 2010 racing suit. Bouts consisted of incremental testing on roller skis (12 km·h-1 at 5° inclination; 11 km·h-1 at 6° inclination and 12 km·h-1at 8° inclination for six minutes).

RESULTS

During increasing intensities, significantly lower values were found for oxygen uptake, minute ventilation, RER and heart rate when wearing the new suit compared to the old one (P<0.05; effect sizes: 0.21-4.00). Core temperature was lower with the new suit during steps 2 and 3 (P<0.05, effect size: 1.22-1.27). Also, mean skin temperature was lower during the last increment (P<0.05, effect size: 0.87).

CONCLUSION

The new 2010 racing suit, developed specifically for the Olympic Winter Games in Vancouver 2010, demonstrated lower values for oxygen uptake, minute ventilation, heart rate, skin and core temperature, ratings of thermal and sweat sensation when compared to the 2009 racing suit.

MSTN mRNA after varying exercise modalities in humans

The aim of this study was to examine the effects of strength and endurance training on myostatin mRNA in the vastus lateralis muscle of healthy and physically active humans. 21 healthy and physically active sports students (static and dynamic knee extensor strength 33 ± 4.5 N/kgBW; 1 185 ± 170 W, respectively; maximum oxygen uptake 52.5 ± 8 ml/kgBW/min) were recruited and randomly assigned to a moderate endurance training group (n=7), a strength training group (n=7) and a control group (n=7). Muscle biopsies were taken from the vastus lateralis muscle 3-5 days before the start as well as at the end of the 12 weeks' training period. Exercise-specific functional improvements after moderate endurance training and strength training were measured for submaximal endurance and for static and dynamic strength of the knee extensor muscles. None of the myostatin mRNA values showed significant pre-post differences or group-specific differences. These results are in contrast to data with sedentary subjects, suggesting that myostatin is necessary for adaptations of skeletal muscle to exercise stress. We conclude that functional improvements after moderate endurance training and strength training can occur without alterations in myostatin mRNA in physically active humans.

Ergogenic effect of hyperoxic recovery in elite swimmers performing high-intensity intervals

This investigation tested the hypothesis that breathing oxygen-enriched air (F(i)O(2) =1.00) during recovery enhances peak (P(peak)) and mean power (P(mean)) output during repeated high-intensity exercise. Twelve elite male swimmers (21 ± 3 years, 192.1 ± 5.9 cm, 79.1 ± 8.2 kg) inhaled either hyperoxic (HOX) or normoxic (NOX) air during 6-min recovery periods between five repetitions of high-intensity bench swimming, each involving 40 maximal armstrokes. Oxygen partial pressure (pO(2)) and saturation (SO(2)), [H(+)], pH, base excess and blood lactate concentration were measured before and after all intervals. The production of the reactive oxygen species (ROS) hydrogen peroxide was measured before, directly after and 15 min after the test. P(peak) and P(mean) with HOX recovery were significantly higher than with NOX throughout the third, fourth and fifth intervals (P<0.001-0.04). With HOX, electromyography activity was lower during the third, fourth and fifth intervals than during the first (P=0.05-0.001), with no such changes in NOX (P=0.99). There were no differences in blood lactate, pH, [H(+)] or base excess and ROS production at any time point with either HOX or NOX recovery. These findings demonstrate that the P(peak) and P(mean) of elite swimmers performing high-intensity intervals can be improved by exposure to oxygen-enriched air during recovery.

Cardio-respiratory and metabolic responses to different levels of compression during submaximal exercise

OBJECTIVE

The effects of knee-high socks that applied different levels of compression (0, 10, 20, 30 and 40 mmHg) on various cardio-respiratory and metabolic parameters during submaximal running were analysed.

METHODS

Fifteen well-trained, male endurance athletes (age: 22.2 ± 1.3 years; peak oxygen uptake: 57.2 ± 4.0 mL/minute/kg) performed a ramp test to determine peak oxygen uptake. Thereafter, all athletes carried out five periods of submaximal running (at approximately 70% of peak oxygen uptake) with and without compression socks that applied the different levels of pressure. Cardiac output and index, stroke volume, arterio-venous difference in oxygen saturation, oxygen uptake, arterial oxygen saturation, heart rate and blood lactate were monitored before and during all of these tests.

RESULTS

Cardiac output (P = 0.29) and index (P = 0.27), stroke volume (P = 0.50), arterio-venous difference in oxygen saturation (P = 0.11), oxygen uptake (P = 1.00), arterial oxygen saturation (P = 1.00), heart rate (P = 1.00) and arterial lactate concentration (P = 1.00) were unaffected by compression (effect sizes = 0.00-0.65).

CONCLUSION

This first evaluation of the potential effects of increasing levels of compression on cardio-respiratory and metabolic parameters during submaximal exercise revealed no effects whatsoever.