Influence of exercise intensity and regional differences in the sudomotor recruitment pattern in exercising prepubertal boys and young men.

We investigated the influence of exercise intensities and regional differences in the sudomotor recruitment pattern in boys. Six prepubertal boys (age 11 ± 1 yr) cycled at light, moderate, and high exercise intensity (35%, 50%, and 65% VOmax) for 30 min in a temperate condition (28 °C, 40% relative humidity). Local sweat rate (ventilated capsule) and number of activated sweat glands (starch-iodine technique) at five body sites were assessed and sweat gland output was calculated.

Dissociation between exercise intensity thresholds: mechanistic insights from supine exercise.

This study tested the hypothesis that the respiratory compensation point (RCP) and breakpoint in deoxygenated [heme] [deoxy[heme], assessed via near-infrared spectroscopy (NIRS)] during ramp incremental exercise would occur at the same metabolic rate in the upright (U) and supine (S) body positions. Eleven healthy men completed ramp incremental exercise tests in U and S. Gas exchange was measured breath-by-breath and time-resolved-NIRS was used to measure deoxy[heme] in the vastus lateralis (VL) and rectus femoris (RF).

The effect of seasonal acclimatization on whole body heat loss response during exercise in a hot humid environment with different air velocity.

Seasonal acclimatization from winter to summer is known to enhance thermoeffector responses in hot-dry environments during exercise whereas its impact on sweat evaporation and core temperature (T) responses in hot-humid environments remains unknown. We, therefore, sought to determine whether seasonal acclimatization is able to modulate whole body sweat rate (WBSR), evaporated sweat rate, sweating efficiency, and thermoregulatory function during cycling exercise in a hot-humid environment (32°C, 75% RH). We also determined whether the increase in air velocity could enhance evaporated sweat rate and sweating efficiency before and after seasonal acclimatization.

Impact of supine versus upright exercise on muscle deoxygenation heterogeneity during ramp incremental cycling is site specific.

Purpose: We tested the hypothesis that incremental ramp cycling exercise performed in the supine position (S) would be associated with an increased reliance on muscle deoxygenation (deoxy[heme]) in the deep and superficial vastus lateralis (VLd and VLs, respectively) and the superficial rectus femoris (RFs) when compared to the upright position (U).

Methods: 11 healthy men completed ramp incremental exercise tests in S and U. Pulmonary [Formula: see text]O was measured breath-by-breath; deoxy[heme] was determined via time-resolved near-infrared spectroscopy in the VLd, VLs and RFs.

Effect of priming exercise and body position on pulmonary oxygen uptake and muscle deoxygenation kinetics during cycle exercise.

We hypothesized that the performance of prior heavy exercise would speed pulmonary oxygen uptake (V̇o) kinetics (i.e., as described by the time constant, [Formula: see text]) and reduce the amplitude of muscle deoxygenation (deoxy[heme]) kinetics in the supine (S) but not upright (U) body position.

Impact of supine exercise on muscle deoxygenation kinetics heterogeneity: mechanistic insights into slow pulmonary oxygen uptake dynamics.

Oxygen uptake (V̇o) kinetics are slowed in the supine (S) position purportedly due to impaired muscle O delivery ([Formula: see text]); however, these conclusions are predicated on single-site measurements in superficial muscle using continuous-wave near-infrared spectroscopy (NIRS). This study aimed to determine the impact of body position [i.e.

Effect of differential muscle activation patterns on muscle deoxygenation and microvascular haemoglobin regulation.

New Findings: What is the central question of this study? Does the presence and extent of heterogeneity in the ratio of O delivery to uptake across human muscles relate specifically to different muscle activation patterns? What is the main finding and its importance? During ramp incremental knee-extension and cycling exercise, the profiles of muscle deoxygenation (deoxy[haemoglobin + myoglobin]) and diffusive O potential (total[haemoglobin + myoglobin]) in the vastus lateralis corresponded to different muscle activation strategies. However, this was not the case for the rectus femoris, where muscle activation and deoxygenation profiles were dissociated and might therefore be determined by other structural and/or functional attributes (e.g.

Autonomic and perceptual thermoregulatory responses to voluntarily engaging in a common thermoregulatory behaviour.

We examined whether partial clothing removal is an effective thermoregulatory behaviour to attenuate both thermoregulatory and perceptual strain in a moderate environment (23 °C, 65% RH) during and after exercise. Ten healthy males (age: 21.9 (0.

Unaltered V̇o kinetics despite greater muscle oxygenation during heavy-intensity two-legged knee extension versus cycle exercise in humans.

Relative perfusion of active muscles is greater during knee extension ergometry (KE) than cycle ergometry (CE). This provides the opportunity to investigate the effects of increased O delivery (Q̇o) on deoxygenation heterogeneity among quadriceps muscles and pulmonary oxygen uptake (V̇o) kinetics. Using time-resolved near-infrared spectroscopy, we hypothesized that compared with CE the superficial vastus lateralis (VL), superficial rectus femoris, and deep VL in KE would have ) a smaller amplitude of the exercise-induced increase in deoxy[Hb + Mb] (related to the balance between V̇o and Q̇o); ) a greater amplitude of total[Hb + Mb] (related to the diffusive O conductance); ) a greater homogeneity of regional muscle deoxy[Hb + Mb]; and ) no difference in pulmonary V̇o kinetics.

Influence of dietary nitrate supplementation on local sweating and cutaneous vascular responses during exercise in a hot environment.

Purpose: We investigated the influence of inorganic nitrate ([Formula: see text]) supplementation on local sweating and cutaneous vascular responses during exercise in hot conditions.

Method: Eight healthy, young subjects were assigned in a randomized, double-blind, crossover design to receive [Formula: see text]-rich beetroot (BR) juice (140 mL/day, containing ~ 8 mmol of [Formula: see text]) and [Formula: see text]-depleted placebo (PL) juice (140 mL/day, containing ~ 0.003 mmol of [Formula: see text]) for 3 days.

Blood flow occlusion-related O extraction "reserve" is present in different muscles of the quadriceps but greater in deeper regions after ramp-incremental test.

It was recently demonstrated that an O extraction reserve, as assessed by the near-infrared spectroscopy (NIRS)-derived deoxygenation signal ([HHb]), exists in the superficial region of vastus lateralis (VL) muscle during an occlusion performed at the end of a ramp-incremental test. However, it is unknown whether this reserve is present and/or different in magnitude in other portions and depths of the quadriceps muscles. We tested the hypothesis that an O extraction reserve would exist in other regions of this muscle but is greater in deep compared with more superficial portions.

Near-infrared spectroscopy of superficial and deep rectus femoris reveals markedly different exercise response to superficial vastus lateralis.

To date our knowledge of skeletal muscle deoxygenation as measured by near-infrared spectroscopy (NIRS) is predicated almost exclusively on sampling of superficial muscle(s), most commonly the (VL-s). Recently developed high power NIRS facilitates simultaneous sampling of deep (i.e.

The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling.

This study investigated the influence of dietary inorganic nitrate (NO) supplementation on pulmonary O uptake (V˙O) and muscle deoxyhemoglobin/myoglobin (i.e. deoxy [Hb + Mb]) kinetics during submaximal cycling exercise.

Greater V˙O2peak is correlated with greater skeletal muscle deoxygenation amplitude and hemoglobin concentration within individual muscles during ramp-incremental cycle exercise.

It is axiomatic that greater aerobic fitness (V˙O) derives from enhanced perfusive and diffusive O conductances across active muscles. However, it remains unknown how these conductances might be reflected by regional differences in fractional O extraction (i.e.

Muscle deoxygenation in the quadriceps during ramp incremental cycling: Deep vs. superficial heterogeneity.

Muscle deoxygenation (i.e., deoxy[Hb + Mb]) during exercise assesses the matching of oxygen delivery (Q̇O2) to oxygen utilization (V̇O2).

Reduction of V̇O2 slow component by priming exercise: novel mechanistic insights from time-resolved near-infrared spectroscopy.

Novel time-resolved near-infrared spectroscopy (TR-NIRS), with adipose tissue thickness correction, was used to test the hypotheses that heavy priming exercise reduces the V̇O2 slow component (V̇O2SC) (1) by elevating microvascular [Hb] volume at multiple sites within the quadriceps femoris (2) rather than reducing the heterogeneity of muscle deoxygenation kinetics. Twelve subjects completed two 6-min bouts of heavy work rate exercise, separated by 6 min of unloaded cycling. Priming exercise induced faster overall V̇O2 kinetics consequent to a substantial reduction in the V̇O2SC (0.

Validation of a high-power, time-resolved, near-infrared spectroscopy system for measurement of superficial and deep muscle deoxygenation during exercise.

Near-infrared assessment of skeletal muscle is restricted to superficial tissues due to power limitations of spectroscopic systems. We reasoned that understanding of muscle deoxygenation may be improved by simultaneously interrogating deeper tissues. To achieve this, we modified a high-power (∼8 mW), time-resolved, near-infrared spectroscopy system to increase depth penetration.