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Michael Wilkinson, Damon Leedale-Brown and Edward M. Winter

Purpose:

We examined the reproducibility of performance and physiological responses on a squash-specific incremental test.

Methods:

Eight trained squash players habituated to procedures with two prior visits performed an incremental squash test to volitional exhaustion on two occasions 7 days apart. Breath-by-breath oxygen uptake ( Vo2) and heart rate were determined continuously using a portable telemetric system. Blood lactate concentration at the end of 4-min stages was assessed to determine lactate threshold. Once threshold was determined, test speed was increased every minute until volitional exhaustion for assessment of maximal oxygen uptake (Vo2max), maximum heart rate (HRmax), and performance time. Economy was taken as the 60-s mean of Vo2 in the final minute of the fourth stage (below lactate threshold for all participants). Typical error of measurement (TEM) with associated 90% confidence intervals, limits of agreement, paired sample t tests, and least products regression were used to assess the reproducibility of scores.

Results:

Performance time (TEM 27 s, 4%, 90% CI 19 to 49 s) Vo2max (TEM 2.4 mL·kg−1·min−1, 4.7%, 90% CI 1.7 to 4.3 mL·kg−1·min−1), maximum heart rate (TEM 2 beats·min−1, 1.3%, 90% CI 2 to 4 beats·min−1), and economy (TEM 1.6 mL·kg−1·min−1, 4.1%, 90% CI 1.1 to 2.8 mL·kg−1·min−1) were reproducible.

Conclusions:

The results suggest that endurance performance and physiological responses to a squash-specific fitness test are reproducible.

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Brian Klucinec, Craig Denegar and Rizwan Mahmood

During the administration of therapeutic ultrasound, the amount of pressure at the sound head-tissue interface may affect the physiological response to and the outcome of treatment. Speed of sonification; size of the treatment area; frequency, intensity, and type of wave; and coupling media are important parameters in providing the patient with an appropriate ultrasound treatment. Pressure variations affect ultrasound transmissivity, yet pressure differences have been virtually unexplored. The purpose of this study was to assess the effects of sound head pressure on acoustic transmissivity. Three trials were conducted whereby pig tissue was subjected to increased sound head pressures using manufactured weights. The weights were added in 100 g increments, starting with 200 g and finishing with 1,400 g. Increased pressure on the transmitting transducer did affect acoustic transmissivity; acoustic energy transmission was increased from 200 g (0.44 lb) up to and optimally at 600 g (1.32 lb). However, there was decreased transmissivity from 700 to 1, 400 g (1.54 to 3.00 lb).

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Charles J. Hardy, Evelyn G. Hall and Perry H. Prestholdt

Two experiments are reported that investigate the mediational role of social influence in the self-perception of exertion. In Experiment 1, subjects performed three 15-min trials on a cycle ergometer at 25%, 50%, and 75% VO2max, both in the presence of another performer (a coactor) and alone. The results indicated that subjects reported lower RPEs when performing with another, particularly at the moderate (50%) intensity. In Experiment 2, subjects performed one 15-min trial at 50% of VO2max, both alone and in the presence of another performer (coactor) exhibiting nonverbal "cues" that the work was either extremely easy or extremely difficult. The results indicated that subjects exposed to the low-intensity cue information reported lower RPEs than when performing alone. Mo significant differences were noted for those subjects exposed to the high-intensity cue information. These findings are discussed in terms of a self-presentational analysis. That such effects were evidenced without physiological responses (VO2, VE, HR) accompanying them supports the notion that psychological variables can play a significant role in the self-perception of exertion. These results, however, are limited to untrained individuals exercising at moderate intensities.

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Jennifer K. Ormerod, Tabatha A. Elliott, Timothy P. Scheett, Jaci L. VanHeest, Lawrence E. Armstrong and Carl M. Maresh

The purposes of this study were to characterize measures of fluid intake and perception of thirst in women over a 6-week period of exercise-heat acclimation and outdoor training and examine if this lengthy acclimation period would result in changes in fluid intake that differ from those previously reported in men utilizing a shorter acclimation protocol of 8–10 days. Voluntary water intake (11–17 °C) and perception of thirst were measured in a group of 5 women (21–26 yr) undergoing exercise-heat acclimation for 90 min/day, 3 days/wk (36 °C, rh 50–70%) and outdoor training 3 days/wk for 6 weeks. Decreased drinking during acclimation was characterized by a decrease in the number of drinks (35 ± 10 to 17 ± 5; p < .05), greater time to first drink (9.9 ± 2.0 to 23.1 ± 4.7 min; p < .05), and a decrease in total volume ingested per week (3310 ± 810 to 1849 ± 446 ml; p < .05) through the 6-week study. Mean perceived thirst measurements remained low and showed only slight variance (3 ± 0.4 to 5 ± 0.4). These observations support a psycho-physiological response pattern different than that previously observed during 8–10 day acclimation protocols in men.

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Kelly R. Rice, Catherine Gammon, Karin Pfieffer and Stewart Trost

Purpose:

The OMNI perceived exertion scale was developed for children to report perceived effort while performing physical activity; however no studies have formally examined age-related differences in validity. This study evaluated the validity of the OMNI-RPE in 4 age groups performing a range of lifestyle activities.

Methods:

206 participants were stratified into four age groups: 6-8 years (n = 42), 9-10 years (n = 46), 11-12 years (n = 47), and 13-15 years (n = 71). Heart rate and VO2 were measured during 11 activity trials ranging in intensity from sedentary to vigorous. After each trial, participants reported effort from the OMNI walk/run scale. Concurrent validity was assessed by calculating within-subject correlations between OMNI ratings and the two physiological indices.

Results:

The average correlation between OMNI ratings and VO2 was 0.67, 0.77, 0.85, and 0.87 for the 6-8, 9-10, 11-12 and 13-15 y age groups, respectively.

Conclusion:

The OMNI RPE scale demonstrated fair to good evidence of validity across a range of lifestyle activities among 6- to 15-year-old children. The validity of the scale appears to be developmentally related with RPE reports closely reflecting physiological responses among children older than 8 years.

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Jon L. Oliver, Neil Armstrong and Craig A. Williams

Purpose:

The purpose of the study was to assess the reliability and validity of a newly developed laboratory protocol to measure prolonged repeated-sprint ability (RSA) during soccer-specific exercise.

Methods:

To assess reliability, 12 youth soccer players age 15.2 ± 0.3 y performed 2 trials of a soccer-specific intermittent-exercise test (SSIET) separated by 3 months. The test was performed on a nonmotorized treadmill. A separate sample of 12 youth soccer players (15.2 ± 0.3 y) completed the SSIET while simultaneously HR, VO2, and blood lactate (BLa) were monitored. The SSIET was designed to replicate the demands of competing in one half of a soccer match while sprint performance was monitored. The test included a 5-s sprint every 2 min.

Results:

The mean coefficient of variation was 2.5% for the total distance covered during the SSIET and 3.8% for the total distance sprinted; measures of power output were less reliable (>5.9%). Participants covered 4851 ± 251 m during the SSIET, working at an average intensity of 87.5% ± 3.2% HRpeak and 70.2% ± 3.1% VO2peak, with ~7mmol/L BLa accumulation. A significant reduction (P < .05) in sprint performance was ob served over the course of the SSIET.

Conclusion:

The SSIET provided a reliable method of assessing prolonged RSA in the laboratory. The distance covered and the physiological responses during the SSIET successfully recreated the demands of competing in a soccer match.

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Claire Rechichi, Brian Dawson and Carmel Goodman

Some reports suggest variation in physiological responses and athletic performance, for female athletes at specific phases of the menstrual cycle. However, inconsistent findings are common due to the inappropriate verification of menstrual cycle phase, small subject numbers, high intra- and interindividual variability in estrogen and progesterone concentration, and the pulsatile secretion of these hormones. Therefore, the oral contraceptive (OC) cycle may provide a more stable environment in which to evaluate the acute effect of reproductive hormones on physiological variables and exercise performance. To date, most of the OC research has compared differences between OC use and nonuse, and few researchers have examined within-cycle effects of the OC. It is also apparent that OC use is becoming far more prevalent in athletes; hence the effect of the different exogenous and endogenous hormonal profiles on athletic performance should be investigated. Research to date identifies potential for variation in aerobic performance, anaerobic capacity, anaerobic power and reactive strength throughout an OC cycle. The purpose of this review is to present and evaluate the current literature on the physiology of exercise and athletic performance during the OC cycle.

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Mindy Millard-Stafford, Linda B. Rosskopf, Teresa K. Snow and Bryan T. Hinson

Twelve highly trained male runners ran 15 km at self-selected pace on a treadmill in warm conditions to demonstrate differences in physiological responses, fluid preferences, and performance when ingesting sports drinks or plain water before and during exercise. One hour prior to the start of running, an equal volume (1,000 ml) of either water or a 6% or an 8% carbohydrate-electrolyte (CE) drink was ingested. Blood glucose was significantly higher 30 min following ingestion of 6% and 8% CE compared to water, significantly lower at 60 min postingestion with both sports drinks than with water, but similar after 7.5 km of the run for all beverages. During the first 13.4 km, oxygen uptake and run times were not different between trials; however, the final 1.6-km performance run was faster with both CE drinks compared to water. Despite a lower preexercise blood glucose, CE consumption prior to and during exercise significantly improved performance in the last 1.6 km of a 15-km run compared to water.

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Matthew T. Wittbrodt, Mindy Millard-Stafford, Ross A. Sherman and Christopher C. Cheatham

Purpose:

The impact of mild hypohydration on physiological responses and cognitive performance following exercise-heat stress (EHS) were examined compared with conditions when fluids were ingested ad libitum (AL) or replaced to match sweat losses (FR).

Methods:

Twelve unacclimatized, recreationally-active men (22.2 ± 2.4 y) completed 50 min cycling (60%VO2peak) in the heat (32°C; 65% RH) under three conditions: no fluid (NF), AL, and FR. Before and after EHS, a cognitive battery was completed: Trail making, perceptual vigilance, pattern comparison, match-to-sample, and letter-digit recognition tests.

Results:

Hypohydration during NF was greater compared with AL and FR (NF: -1.5 ± 0.6; AL: -0.3 ± 0.8; FR: -0.1 ± 0.3% body mass loss) resulting in higher core temperature (by 0.4, 0.5 °C), heart rate (by 13 and 15 b·min-1), and physiological strain (by 1.3, 1.5) at the end of EHS compared with AL and FR, respectively. Cognitive performance (response time and accuracy) was not altered by fluid condition; however, mean response time improved (p < .05) for letter-digit recognition (by 56.7 ± 85.8 ms or 3.8%; p < .05) and pattern comparison (by 80.6 ± 57.4 ms or 7.1%; p < .001), but mean accuracy decreased in trail making (by 1.2 ± 1.4%; p = .01) after EHS (across all conditions).

Conclusions:

For recreational athletes, fluid intake effectively mitigated physiological strain induced by mild hypohydration; however, mild hypohydration resulting from EHS elicited no adverse changes in cognitive performance.

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Matthew S. Hickey, David L. Costill and Scott W. Trappe

This study investigated the influence of drink carbonation and carbohydrate content on ad libitum drinking behavior and body fluid and electrolyte responses during prolonged exercise in the heat. Eight competitive male runners completed three 2-hr treadmill runs at 60% VO2max in an environmental chamber maintained at 30 C° and 40% RH. Three test drinks were used: 8% carbohydrate, low carbonation (8%-C); 8% carbohydrate, noncarbonated (8%-NC), and water (0%-NC). Blood samples were taken preexercise (0), at 60 and 120 min of exercise, and at 60 min of recovery (+60 min). The data suggest that while reports of heartburn tend to be higher on 8% carbohydrate drinks than on 0%-NC, this does not appear to be a function of drink carbonation. Similarly, the increased frequency of heartbum did not significantly reduce fluid consumption either during exercise or during a 60-min recovery period. Importantly, no differences were observed between fluid and electrolyte, or thermoregulatory responses to the three sport drinks. Thus, consumption of low-carbonation beverages does not appear to significantly influence drinking behavior or the related physiological responses during prolonged exercise in the heat.