European journal of applied physiology
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Eur. J. Appl. Physiol. · Nov 2002
Comparative StudyOxygen uptake and heart rate kinetics during heavy exercise: a comparison between arm cranking and leg cycling.
This study examined the oxygen uptake (VO(2)) and heart rate (HR) kinetics during arm cranking and leg cycling at work rates above the anaerobic threshold (AT). Ten untrained male subjects [21.6 (1.3) years] completed two 7 min 15 s constant-load arm cranking and two leg cycling tests at a power output halfway between the mode-specific AT and peak VO(2). ⋯ The VO(2) slow component (VO(2SC)) accounted for a significantly (P < 0.001) greater percentage of the total exercise response during arm cranking [23.8 (1.6)%] than during leg cycling [14.2 (1.5)%]. The greater relative VO(2SC) and the slower VO(2) tau with arm exercise are consistent with a greater recruitment of metabolically inefficient type II muscle fibres during arm cranking than during leg cycling.
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The paraspinal muscle responses for unexpected and expected upper limb loading were investigated by surface EMG of 20 healthy volunteers. The simultaneous trunk and hand accelerations with paraspinal, biceps brachii and soleus muscles EMG were measured in four subjects. A short-latency response of approximately 50 ms was observed in paraspinal muscles. ⋯ In conclusion, visual expectation shortens the latency and decreases the magnitude of the paraspinal muscle response to sudden upper limb loading. Also, the trial repetition has an effect on reflex latency if visual information is available. These results indicate that anticipation modulates the reflex control of paraspinal muscles, which may be significant in understanding spinal function.
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Eur. J. Appl. Physiol. · Oct 2002
Breath-by-breath fluctuations of pulmonary gas exchange and ventilation in COPD patients.
The purpose of the study was to characterise statistically the inherent fluctuations in breath-by-breath measurements of pulmonary gas exchange (oxygen uptake and carbon dioxide output, V*O2 and V*CO2, respectively) and pulmonary ventilation (V*E) in patients with chronic obstructive pulmonary disease (COPD) and to compare them with those of healthy control subjects. Thirty subjects with COPD [mean (SD): 67 (6) years old; forced expiratory volume in 1 min, FEV1 1.25( 0.18) l; 42 (6)% predicted FEV1] and 12 healthy subjects [31 (3) years old; FEV1 3.62 (0.54) l; 99 (8)% predicted FEV1] performed exercise tests on a cycle ergometer at a constant work rate of moderate intensity. ⋯ Its magnitude varied among variables, but was independent of the signal amplitude for the same subject and variable. With ratios of amplitude of fluctuation:signal of around 10%, typical of the patients studied, the resolution of time constants and amplitude were congruent with 9 s and congruent with 100 ml.min(-1), respectively for V*O2 or V*CO2 with one repetition.
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Eur. J. Appl. Physiol. · Aug 2002
Comparative StudyUpper trapezius muscle mechanomyographic and electromyographic activity in humans during low force fatiguing and non-fatiguing contractions.
The purposes of this study were firstly to compare and investigate localised fatigue in the upper trapezius muscle in various arm positions as assessed by mechanomyographic (MMG) and surface electromyographic (EMG) signals and secondly to study the effects of different normalisation methods on MMG and EMG signals during non-fatiguing and fatiguing low level isometric contractions. The MMG, EMG and rate of perceived exertion were recorded from 11 subjects in five arm positions (0 degrees abduction and 0 degrees flexion, 45 degrees and 90 degrees flexion, 45 degrees and 90 degrees abduction) with different bilateral arm loads during 3 s for non-fatiguing (0-0.5-1 kg hand-load) and 3 min for fatiguing contractions (1 kg hand-load). The root mean square (RMS), average rectified value (ARV), mean power frequency (MNF), and median power frequency (MDF) of the MMG and EMG signals were computed and normalised with respect to the initial values obtained in the current arm position or in the reference position (0 degrees abduction and 0 degrees flexion) corresponding to the normal postural activity of the trapezius muscle. ⋯ For non-fatiguing contractions, normalisation to the current arm position entailed the loss of dynamic amplitude changes suggesting that a single reference contraction in the middle part of the range of movement is enough for proper normalisation of EMG and MMG signals. For fatiguing contractions, normalisation of the EMG and MMG to some extent can lead to a misleading interpretation. Assessment of the upper trapezius muscle by means of MMG may be valuable in ergonomics.