Subjective ratings and performance in the heat and after sleep deprivation

Background: It has been shown that endurance performance after one night of sleep deprivation is not compromised despite the feeling of fatigue and that, in contrast, performance in the heat deteriorates even though people may feel good. However, it is essentially unknown how the estimation of performance capabilities relate to actual...

The steep ramp test in healthy children and adolescents: Reliability and validity

PURPOSE: This study aimed to examine the reliability and validity of the steep ramp test (SRT), a feasible, maximal exercise test on a cycle ergometer that does not require the use of respiratory gas analysis, in healthy children and adolescents.METHODS: Seventy-five children were randomly divided in a reliability group (n = 37, 17 boys and 20...

Meeting the 60-min physical activity guideline: Effect of operationalization

Purpose: To investigate the effect of guideline operationalization in terms of intensity threshold, bout duration, and days on the proportion of children meeting the health-related 60-min physical activity guideline using a subjective and an objective assessment method. Methods: Five hundred and twenty-one children (6-11 yr) completed a physical...

Heat strain and gross efficiency during endurance exercise after lower, upper, or whole body precooling in the heat

The maximal power that muscles can generate is reduced at low muscle temperatures. However, in prolonged heavy exercise in the heat, a high core temperature may be the factor limiting performance. Precooling has been shown to delay the attainment of hyperthermia. It is still unclear if the whole body should be cooled or if the active muscles...

Influence of inspiratory resistance on performance during graded exercise tests on a cycle ergometer

Due to more stringent requirements to protect personnel against hazardous gasses, the inspiratory resistance of the present generation of respiratory protective devices tends to increase. Therefore an important question is to what extent inspiratory resistance may increase without giving problems during physical work. In this study the effects...

Maximal oxygen uptake during cycling is reduced in moving environments: Consequencies for motion-induced fatigue

In previous studies on physical fatigue during simulated ship movements, the apparent exhaustion of subjects after experimentation suggested that the traditional index of physical workload, oxygen consumption expressed as the percentage of peak oxygen consumption (VO2-peak) measured in a separate graded exercise test (GXT), underestimates...

Force direction and physical load in dynamic pushing and pulling

In pushing and pulling wheeled carts, the direction of force exertion may, beside the force magnitude, considerably affect musculoskeletal loading. This paper describes how force direction changes as handle height and force level change, and the effects this has on the loads on the shoulder and low back. Eight subjects pushed against or pulled...

Estimation of beat-to-beat changes in stroke volume from arterial pressure: A comparison of two pressure wave analysis techniques during head- up tilt testing in young, healthy men

Objective: The aim of this study was to compare beat-to-beat changes in stroke volume (SV) estimated by two different pressure wave analysis techniques during orthostatic stress testing: pulse contour analysis and Modelflow, ie, simulation of a three-element model of aortic input impedance. Methods: A reduction in SV was introduced in eight...

Finapres tracking of systolic pressure and baroreflex sensitivity improved by waveform filtering

Objective. Arterial pressure waveforms distort between brachial and finger arteries, causing differences mainly in systolic pressure. Distortion, reportedly, can be removed by applying a waveform filter to the finger pressure. Design. We analysed the data from two studies that detected discrepancies in systolic tracking between Finapres and...

Effects of moderate energy restriction on physical performance and substrate utilization in non-obese men

Energy restriction (ER) has shown to be an effective 'anti-aging' factor in rodents, resulting in an increased life span and preventing or delaying the occurrence of many age-related diseases in rodents. As a part of a feasibility study on the potential application of ER in humans, we studied the effects of moderate ER on physical performance in...

The relative influence of physical fitness, acclimatization state, anthropometric measures and gender on the individual reaction to heat stress

An experiment was set up to quantify the relative influence of fitness, acclimatization, gender and anthropometric measures on physiological responses to heat stress. For this purpose, 12 male and 12 female subjects were exposed to a neutral [ambient temperature (T(a)) 21°C, relative humidity (r.h. 50%)], a warm, humid (T(a) 34°C, r.h. 80%) and...

Maximum oxygen uptake in healthy nonathletic males

Maximum oxygen uptake ( {Mathematical expression} max), maximum heart rate (MHR), blood lactic acid (LA) and pH were measured during bicycle ergometer exercise in 52 men, 22 to 60 years old, engaged in clerical and light manual work (prison personnel and prisoners in the Netherlands). {Mathematical expression} max decreases with, age, but less...