European journal of applied physiology
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Eur. J. Appl. Physiol. · Oct 2013
Effects of step duration in incremental ramp protocols on peak power and maximal oxygen consumption.
Morton (J Sport Sci 29:307-309, 2011) proposed a model of the peak power attained in ramp protocol ([Formula: see text]) that included critical power (CP) and anaerobic capacity as constants, and mean ramp slope (S) as variable. Our hypothesis is that [Formula: see text] depends only on S, so that Morton's model should be applicable in all types of ramps. The aim of this study was to test this hypothesis by validating Morton's model using stepwise ramp tests with invariant step increment and increasing step duration. ⋯ Morton's model is a good descriptor of the mechanics of ramp tests. Further developments of Morton's model demonstrated that, whereas [Formula: see text] is a protocol-dependent variable, the difference between [Formula: see text] and CP is a constant, so that their values do not depend on the protocol applied.
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Eur. J. Appl. Physiol. · Sep 2013
Variable resistance training promotes greater fatigue resistance but not hypertrophy versus constant resistance training.
Loading using variable resistance devices, where the external resistance changes in line with the force:angle relationship, has been shown to cause greater acute neuromuscular fatigue and larger serum hormone responses. This may indicate a greater potential for adaptation during long-term training. Twelve (constant resistance group) and 11 (variable resistance group) men completed 20 weeks of resistance training with 10 men as non-training controls. ⋯ Acute loading-induced responses were assessed by concentric and isometric force, serum hormone concentrations and phosphorylation of intramuscular signalling proteins (0-30 min post-loading). Greater acute decreases in force (P < 0.05-0.01), and greater increases in serum testosterone and cortisol concentration (P < 0.05) and ERK 1/2 phosphorylation (P < 0.05) were observed following variable resistance loadings before and after training. Greater training-induced improvements in fatigue resistance occurred in the variable resistance training group, which may be due to greater acute fatigue and physiological responses during variable versus constant resistance loadings.
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Eur. J. Appl. Physiol. · Sep 2013
Relationship between core temperature, skin temperature, and heat flux during exercise in heat.
This paper investigates the relationship between core temperature (T c), skin temperature (T s) and heat flux (HF) during exercise in hot conditions. ⋯ Algorithms for T c measurement are location-specific and their accuracy is dependent, to a large degree, on sensor placement.
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Eur. J. Appl. Physiol. · Aug 2013
Psychoneuroendocrine alterations during 5 days of head-down tilt bed rest and artificial gravity interventions.
This study aimed to investigate psychological stress and endocrine responses during 5 days of head-down tilt bed rest (HDTBR) with or without the impact of artificial gravity (AG). Participants were assigned to one of three bed-rest-protocols either with (i) no centrifugation, (ii) continuous 30 min (AG1) or (iii) discontinuous 6 × 5 min (AG2) centrifugation periods at 1G in the center of mass periods. Centrifugations were performed daily in one session. ⋯ These results indicate that 5 days of HDT alone is not a major stressor and accordingly resulted only in moderate changes of neuroendocrine responses over time. However, daily centrifugation for a continuous duration of 30 min induced a significant neuroendocrine response, which was not subject to a habituation as compared with daily but intermittent centrifugation for 6 × 5 min. Discontinuous centrifugation is better tolerated and associated with lower adrenocortical stress responses during HDTBR.
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Eur. J. Appl. Physiol. · Jul 2013
Randomized Controlled TrialEffect of acute DHEA administration on free testosterone in middle-aged and young men following high-intensity interval training.
With advancing age, plasma testosterone levels decline, with free testosterone levels declining more significantly than total testosterone. This fall is thought to underlie the development of physical and mental weakness that occurs with advancing age. In addition, vigorous exercise can also lower total and free testosterone levels with the decline greatest in physically untrained men. ⋯ Total testosterone and DHEA-S dropped significantly until 24 h after HIIT for both age groups, while free testosterone of DHEA-supplemented middle-aged men remained unaffected. These results demonstrate acute oral DHEA supplementation can elevate free testosterone levels in middle-aged men and prevent it from declining during HIIT. Therefore, DHEA supplementation may have significant benefits related to HIIT adaptation.