European journal of applied physiology and occupational physiology
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Eur J Appl Physiol Occup Physiol · Jan 1995
Clinical TrialDoes the threshold of transcutaneous partial pressure of carbon dioxide represent the respiratory compensation point or anaerobic threshold?
On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (VE) to CO2 output (VCO2) rises, which coincides with changes of arterial partial pressure of carbon dioxide (PaCO2). Since PaCO2 changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO2,tc) RCP may be estimated by PCO2,tc measurement. Few available studies, however, have dealt with comparisons between PCO2,tc threshold (TAT) and lactic, ventilatory or gas exchange threshold (VAT), and the results have been conflicting. ⋯ At TAT, power output [P, 294 (SD 40) W], VO2 [4.18 (SD 0.57) l.min.1] and [la(-)] [4.40 (SD 0.64) mmol.l-1] were significantly higher than those at VAT[P 242 (SD 26) W, VO2 3.56 (SD 0.53) l.min-1 and [la(-)]b 3.52 (SD 0.75), mmol.l-1 respectively], but close to those at RCP [P 289 (SD 37) W; VO2 3.97 (SD 0.43) l.min-1 and [la(-)]b 4.19 (SD 0.62) mmol.l-1, respectively]. Accordingly, linear correlation and regression analyses showed that P, VO2 and [la(-)]b at TAT were closer to those at RCP than at VAT. In conclusion, the TAT reflected the RCP rather than VAT during rapidly increasing incremental exercise.
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Eur J Appl Physiol Occup Physiol · Jan 1994
Body mass, body composition and sleeping metabolic rate before, during and after endurance training.
Metabolic rate, more specifically resting metabolic rate (RMR) or sleeping metabolic rate (SMR), of an adult subject is usually expressed as a function of the fat-free mass (FFM). Chronic exercise is thought to increase FFM and thus to increase RMR and SMR. We determined body mass (BM), body composition, and SMR before, during, and after an endurance training programme without interfering with energy intake. ⋯ Mean SMR before and after 40 weeks training was 6.5 (SD 0.7) and 6.2 (SD 0.6) MJ.day-1 (P < 0.05). The decrease in SMR was related to the decrease in BM (r = 0.62, P = 0.001). At 90 weeks, when most subjects had not trained for nearly a year, BM and SMR were not significantly different from the initial value while FM and FFM had not changed since week 40 of training.(ABSTRACT TRUNCATED AT 250 WORDS)
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Eur J Appl Physiol Occup Physiol · Jan 1994
Electrophysiological and psychophysical quantification of temporal summation in the human nociceptive system.
Animal experiments have shown that the nociceptive reflex can be used as an indicator of central temporal integration in the nociceptive system. The aim of the present study on humans was to investigate whether the nociceptive reflex, evoked by repetitive strong electrical sural nerve stimuli, increased when summation was reported by the volunteers. The reflexes were recorded from the biceps femoris and rectus femoris muscles in eight volunteers following a series of stimulations at 0.1, 1, 2, and 3 Hz. ⋯ Furthermore, the threshold for psychophysical summation could be determined. This threshold (stimulus intensity) decreased when the stimulus frequency (1-5 Hz) of the five consecutive stimuli was increased. The nociceptive reflex and the psychophysical summation threshold might be used to clarify and quantify aspects of temporal summation within the human nociceptive system.
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Eur J Appl Physiol Occup Physiol · Jan 1994
Effects of training and acclimation on heat tolerance in exercising men wearing protective clothing.
This study examined the effectiveness of endurance training and heat acclimation in reducing the physiological strain imposed by exercising in the heat while wearing protective clothing. Seven young men underwent 8 weeks of physical training [60-80% maximal aerobic power (VO2max) for 30-45 min.day-1, 3-4 days.week-1 at < 25 degrees C] followed by 6 days of heat acclimation (45-55% VO2max for 60 min.day-1 at 40 degrees C, 30% relative humidity). Nine other young men underwent corresponding periods of control observation and heat acclimation. ⋯ Training- or acclimation-induced increases of sweat secretion (an average increment of 0.14-0.23 kg.h-1) were not accompanied by any statistically significant increase in sweat evaporation when wearing NBC protective clothing. Moreover, tolerance times were unchanged in either normal combat (116-120 min) or NBC protective clothing (47-52 min). We conclude that neither endurance training nor heat acclimation do much to improve exercise tolerance when wearing NBC protective clothing in hot environments, because any added sweat secretion decreases blood volume and increases discomfort without augmenting body cooling.
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Eur J Appl Physiol Occup Physiol · Jan 1993
Cardiorespiratory response at the onset of passive leg movements during sleep in humans.
To examine the ventilatory response at the onset of passive leg movements during sleep in man and the concomitant changes in cardiac output (Qc), five healthy male subjects had their knee joints extended and flexed alternately at a frequency of about 60.min-1 for about 8 s. Minute ventilation (VI), respiratory frequency, tidal volume, end-tidal partial pressure of carbon dioxide and of oxygen, stroke volume (SV), heart rate (fc) and Qc were measured before, during and after passive leg movement during sleep stage III or IV (SLEEP). These values were compared with those of the awake condition (AWAKE). ⋯ Four of the five subjects showed a larger increase in ventilation during SLEEP compared with AWAKE. The fc increased significantly (P < 0.05) at the beginning of the passive movement in all cases, while SV showed an increase or decrease so that Qc showed no significant change in either condition. These results would suggest that afferent drive from moving limbs could produce an increase in ventilation without any change in Qc.