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This study aims to compare cardiorespiratory kinetics as a response to a standardised work rate protocol with pseudo-random binary sequences between cycling and walking in young healthy subjects. Muscular and pulmonary oxygen uptake (...O2) kinetics as well as heart rate kinetics were expected to be similar for walking and cycling. Cardiac data and ...O2 of 23 healthy young subjects were measured in response to pseudo- random binary sequences. Kinetics were assessed applying time series analysis. Higher maxima of cross-correlation functions between work rate and the respective parameter indicate faster kinetics responses. Muscular ...O2 kinetics were estimated from heart rate and pulmonary ...O2 using a circulatory model. Muscular (walking vs. cycling [mean ± SD in arbitrary units]: 0.40 ± 0.08 vs. 0.41 ± 0.08) and pulmonary ...O2 kinetics (0.35 ± 0.06 vs. 0.35 ± 0.06) were not different, although the time courses of the cross-correlation functions of pulmonary ...O2 showed unexpected biphasic responses. Heart rate kinetics (0.50 ± 0.14 vs. 0.40 ± 0.14; P = 0.017) was faster for walking. Regarding the biphasic cross-correlation functions of pulmonary ...O2 during walking, the assessment of muscular ...O2 kinetics via pseudo-random binary sequences requires a circulatory model to account for cardio-dynamic distortions. Faster heart rate kinetics for walking should be considered by comparing results from cycle and treadmill ergometry. [ABSTRACT FROM AUTHOR]

Pulmonary oxygen uptake (...O2) kinetics and heart rate kinetics are influenced by age and fitness. Muscular ...O2 kinetics can be estimated from heart rate and pulmonary ...O2. In this study the applicability of a test using pseudo-random binary sequences in combination with a model to estimate muscular ...O2 kinetics was tested. Muscular ...O2 kinetics were expected to be faster than pulmonary ...O2 kinetics, slowed in aged subjects and correlated with maximum ...O2 and heart rate kinetics. 27 elderly subjects (73±3 years; 81.1±8.2kg; 175±4.7cm) participated. Cardiorespiratory kinetics were assessed using the maximum of cross-correlation functions, higher maxima implying faster kinetics. Muscular ...O2 kinetics were faster than pulmonary ...O2 kinetics (0.31 ±0.1 vs. 0.29 + 0.1 s; p = 0.004). Heart rate kinetics were not correlated with muscular or pulmonary ...O2 kinetics or maximum ...O2. Muscular VO2 kinetics correlated with maximum ...O2 (r=0.35; p = 0.033). This suggests, that muscular ...O2 kinetics are faster than estimates from pulmonary ...O2 and related to maximum ...O2 in aged subjects. In the future this experimental approach may help to characterize alterations in muscular ...O2 under various conditions independent of motivation and maximal effort. [ABSTRACT FROM AUTHOR]

Essential hypertension (EH) is a widespread disease and might be prevalent in apnea divers and master athletes. Little is known about the influence of EH and the antihypertensive drugs (AHD) on cardiovascular reactions to combined breath hold (BH) and exercise. In this pilot study, healthy divers (HCON) were compared with treated hypertensive divers with regard to heart rate (HR) and mean blood-pressure (MAP) responses to BH, exercise and the combination of both. Ten subjects with EH and ten healthy divers were tested. 3 different 20s stimuli were applied: BH combined with 30W or 150W and 150W without BH. The time-charts during the stress intervals and during recovery were compared. Subjects treated with an angiotensin-converting enzyme (ACE) inhibitor showed higher changes for MAP values if breath hold was performed. HR responses were obviously changed if a β-blocker was part of the medication. One subject showed extreme MAP responses to all stimuli and conspicuous HR if BH was involved. The modulation of HR-/MAP-response in EH subjects depends on the mechanisms of antihypertensive agents. The combination of an ACE inhibitor and a β-blocker may give the best protection. It is recommended to include short apnea tests in the fitness-to-dive examination to individually predict potential endangerment. [ABSTRACT FROM AUTHOR]