Warm-up practices in elite snowboard athletes.

Purpose: The purpose of this project was to observe current warm-up practices in snowboard athletes and evaluate their physiological impact before competition.

Methods: An observational design was used to monitor 4 athletes (2 female) at an Open National Snowboard Cross Championships. Activity patterns, core temperature, heart rate (HR), and time between warm-up and competition were measured.

Prefrontal cortex oxygenation is preserved and does not contribute to impaired neuromuscular activation during passive hyperthermia.

We investigated the role of passive hyperthermia upon motor unit activation and prefrontal cortex oxygenation. Six healthy males were passively heated, using a liquid conditioning garment in a hot environment (35 degrees C, 50% relative humidity). Maximal force output and voluntary activation were examined during a 10 s maximal isometric knee extension.

Hypervolemia and blood alkalinity: effect on physiological strain in a warm environment.

Purpose: To evaluate the influence of acute hypervolemia, achieved through the ingestion of a sodium citrate-rich beverage, on cardiovascular strain and thermoregulatory function, during moderate-intensity aerobic exercise in a warm environment. Sodium citrate's ability to increase buffering capacity was also assessed.

Methods: Twelve endurance-trained athletes completed two blind randomized treatment trials, separated by a minimum of seven days, on a cycle ergometer under heat stress (30.

Effects of varying post-warm-up recovery time on 200-m time-trial swim performance.

Context: Warm-up before athletic competition might enhance performance by affecting various physiological parameters. There are few quantitative data available on physiological responses to the warm-up, and the data that have been reported are inconclusive. Similarly, it has been suggested that varying the recovery period after a standardized warm-up might affect subsequent performance.

Using microtechnology to monitor thermal strain and enhance performance in the field.

Wireless microtechnologies are rapidly emerging as useful tools for sport scientists to move their work out of the laboratory and into the field. The purpose of this report is to describe some of the practical aspects of using ingestible radiotelemetric temperature sensors in sport physiology. Information is also presented to demonstrate the utility of this technology in understanding individual differences in coping with environmental stress, optimizing heat adaptation, and fine-tuning competition strategy (pacing).

Local cold acclimation during exercise and its effect on neuromuscular function of the hand.

Most acclimation research is performed on resting individuals, whereas in real life, cold exposure is often accompanied by physical activity. We examined the effects of 2 weeks of repeated cold exposure of the hand with or without an elevated core temperature from exercise on neuromuscular function of the first dorsal interosseus (FDI) muscle and manual performance of the hand. The experimental group (4 female, 6 male; age, 25.

Aerobic influence on neuromuscular function and tolerance during passive hyperthermia.

Purpose: To determine the role of aerobic fitness on central neuromuscular activation and maximal voluntary contractile force during hyperthermia.

Methods: Thirty-seven healthy males in three distinct groups based on aerobic fitness and training history were passively heated using a liquid conditioning garment in a hot (35 degrees C, 50% RH) environment with the intention of testing neuromuscular function with whole-body hyperthermia. Of these initial participants, 11 of the 13 highly fit (HF; VO2max = 71.

Central and peripheral factors in thermal, neuromuscular, and perceptual adaptation of the hand to repeated cold exposures.

We investigated the role of central and peripheral factors in repeated cold exposure of the hand and their effects on temperature response, neuromuscular function, and subjective thermal sensation. Eleven subjects immersed their left hand repeatedly in 8 degrees C cold water for 30 min, 5 d/week, for 2 weeks. Before and following the 2 weeks of exposure, neuromuscular function, blood markers, thermal sensation, and temperature responses of both acclimated (left) and control (right) hands were tested.

Voluntary muscle activation is impaired by core temperature rather than local muscle temperature.

Fatigue during hyperthermia may be due in part to a failure of the central nervous system to fully activate the working muscles. We investigated the effects of passive hyperthermia on maximal plantar flexor isometric torque (maximal isometric voluntary contraction) and voluntary activation to determine the roles of local skin temperature, core temperature, and peripheral muscle temperature in fatigue. Nine healthy subjects were passively heated from 37.

Effect of cold-induced vasodilatation in the index finger on temperature and contractile characteristics of the first dorsal interosseus muscle during cold-water immersion.

We investigated whether cyclic elevations in index finger temperature (cold-induced vasodilatation, CIVD) during prolonged cold exposure correlated with hand temperature and neuromuscular function. Evoked twitch force of the first dorsal interosseus (FDI) muscle was measured every minute in eight males and four females [age 25.4 (5.

Monitoring individual erector spinae fatigue responses using electromyography and near infrared spectroscopy.

This study examined the utility of electromyography and near-infrared spectroscopy (NIRS) in assessing m. erector spinae activity during the Biering-Sorensen Back Muscle Endurance (BSME) test. Six men and four women (27.

Multiple triggers for hyperthermic fatigue and exhaustion.

It has been proposed that a critical body temperature exists at which muscle activation is impaired through a direct effect of high brain temperature decreasing the central drive to exercise, but other factors may also inhibit performance in the heat. An integrative physiological model is presented to stimulate research into mechanisms of hyperthermic fatigue and exhaustion.

Passive hyperthermia reduces voluntary activation and isometric force production.

It has been suggested that a critically high body core temperature may impair central neuromuscular activation and cause fatigue. We investigated the effects of passive hyperthermia on maximal isometric force production (MVC) and voluntary activation (VA) to determine the relative roles of skin (T(sk)) and body core temperature ( T(c)) on these factors. Twenty-two males [VO(2max)=64.

Lowering of skin temperature decreases isokinetic maximal force production independent of core temperature.

Based on studies using maximal isometric contractions, it is suggested that fatigue may be elicited due to hyperthermia-induced impairments in central neuromuscular activation. We investigated the effects of passive hyperthermia on isokinetic maximal force production. Twenty young healthy males [peak oxygen uptake 52.

The effects of deer antler velvet extract or powder supplementation on aerobic power, erythropoiesis, and muscular strength and endurance characteristics.

To determine the effects of deer antler velvet on maximal aerobic performance and the trainability of muscular strength and endurance, 38 active males were randomly assigned in a double-blind fashion to either deer antler velvet extract (n = 12), powder (n = 13), or placebo groups (n = 13). Subjects were tested prior to beginning supplementation and a 10-week strength program, and immediately post-training. All subjects were measured for circulating levels of testosterone, insulin-like growth factor, erythropoietin, red cell mass, plasma volume, and total blood volume.

Responsiveness of thermal sensors to nonuniform thermal environments and exercise.

Background: We investigated the utility of finger temperature, hand heat flux, and mean skin temperature as indices of overall thermal balance during nonuniform thermal manipulations combined with exercise, with a view to identifying useful feedback sites for input into personal thermal control systems.

Methods: There were 16 subjects who performed 4 x 30 s of 120% VO2peak cycling with a 4-min recovery. During recovery, subjects either received no cooling (CON), upper-body cooling (UC), or upper-body cooling combined with leg heating (UCLH) using a multi-zone liquid conditioning garment.

The relationship between maximal jump-squat power and sprint acceleration in athletes.

This study investigated the relationship between sprint start performance (5-m time) and strength and power variables. Thirty male athletes [height: 183.8 (6.

Temperature effects on the contractile characteristics and sub-maximal voluntary isometric force production of the first dorsal interosseus muscle.

Cooling of a muscle has a detrimental effect on its force, power and contraction velocity, but may improve force control during precision movements by reducing physiological tremor. We investigated if the contractile characteristics of the first dorsal interosseus muscle (FDI) were linked to voluntary force control in warm and hypothermic conditions. Evoked peak twitch force, force at repetitive stimulation of 10 and 20 Hz, and submaximal force control at 25 and 50% maximal voluntary contraction (MVC) of the FDI were measured with cooled [mean (SD); 17.