European journal of applied physiology
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Eur. J. Appl. Physiol. · Aug 2006
Randomized Controlled Trial Comparative StudyAdaptations to endurance training in the healthy elderly: arm cranking versus leg cycling.
The effect in healthy elderly subjects of cycle ergometer or arm ergometer training on peak oxygen consumption (VO(2peak)) and ventilatory threshold (VT) was studied. The aim was to determine the benefit of each training modality on specific and cross exercise capacity. The cross-effect was also evaluated as an index of the central nature of the adaptive response to training. ⋯ The results indicate that aerobic training brought about with different muscle masses, produce similar improvements in maximal and submaximal exercise capacity. Roughly half of such improvements are specific to exercise mode, which suggests peripheral adaptations to training. The other half is non-specific since it influences also the alternative exercise modality, and is probably due to central adaptations.
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Eur. J. Appl. Physiol. · Jun 2006
Randomized Controlled TrialHuman skeletal muscle structure and function preserved by vibration muscle exercise following 55 days of bed rest.
Prolonged immobilization of the human body results in functional impairments and musculoskeletal system deconditioning that may be attenuated by adequate muscle exercise. In a 56-day horizontal bed rest campaign involving voluntary males we investigated the effects of vibration muscle exercise (RVE, 2x6 min daily) on the lower limb skeletal muscles using a newly designed foot plantar trainer (Galileo Space) for use at supine position during bed rest. The maximally voluntary isometric plantar flexion force was maintained following regular RVE bouts during bed rest (controls -18.6 %, P<0.05). ⋯ RVE training increased the activity-dependent expression of nitric oxide synthase type 1 immunofluorescence at SOL and VL myofiber membranes. These data provide evidence for the beneficial effects of RVE training on the deconditioned structure and function of the lower limb skeletal muscle. Daily short RVE should be employed as an effective atrophy countermeasure co-protocol preferentially addressing postural calf muscles during prolonged clinical immobilization or long-term human space missions.
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Eur. J. Appl. Physiol. · Jun 2006
Changes in muscle T2 relaxation properties following spinal cord injury and locomotor training.
Magnetic resonance (MR) is frequently used to study structural and biochemical properties of skeletal muscle. Changes in proton transverse relaxation (T2) properties have been used to study muscle cellular damage, as well as muscle activation during exercise protocols. In this study, we implemented MR imaging to characterize the T2 relaxation properties of rat hindlimb muscles following spinal cord injury (SCI) and locomotor training. ⋯ Both training paradigms, treadmill and cycling training, accelerated the recovery of soleus muscle T2. As a result, soleus muscle T2 recovered back to pre-injury values within 3 weeks of training in both training groups. Finally, in vitro histological assessments of rat skeletal muscles demonstrated that there was no apparent muscle injury in any of the muscles studied at 1 week post-SCI.
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Eur. J. Appl. Physiol. · May 2006
Influence of lung volume, glossopharyngeal inhalation and P(ET) O2 and P(ET) CO2 on apnea performance in trained breath-hold divers.
Breath-hold divers train and compete in maximal apnea performance. Glossopharyngeal inhalation (GI) is commonly used to increase lung volume above vital capacity (VC) prior to apnea. We investigated the hypothesis that this practice would increase apnea performance and relaxed airway pressure. ⋯ Likewise, dynamic apnea time was higher at VC + GI (97+/-27 s) than at VC (78+/-14 s, P<0.05) and 85% VC (71+/-17 s, P<0.05). P (ET) O(2) values reached 3.5+/-0.6 kPa at the end of dry static apnea bouts and this was not different from dynamic apnea when taking hydrostatic pressure at swimming depth into account (3.7+/-0.6 kPa, P=0.48). In conclusion, GI increases lung volume, relaxed airway pressure and apnea performance in well-trained breath-hold divers.
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Eur. J. Appl. Physiol. · Mar 2006
The postural reduction in middle cerebral artery blood velocity is not explained by PaCO2.
In the normocapnic range, middle cerebral artery mean velocity (MCA Vmean) changes approximately 3.5% per mmHg carbon-dioxide tension in arterial blood (PaCO2) and a decrease in PaCO2 will reduce the cerebral blood flow by vasoconstriction (the CO2 reactivity of the brain). When standing up MCA Vmean and the end-tidal carbon-dioxide tension (PETCO2) decrease, suggesting that PaCO2 contributes to the reduction in MCA Vmean. In a fixed body position, PETCO2 tracks changes in the PaCO2 but when assuming the upright position, cardiac output (Q) decreases and its distribution over the lung changes, while ventilation (VE) increases suggesting that PETCO2 decreases more than PaCO2. ⋯ When standing up, MCA Vmean (from 65.3+/-3.8 to 54.6+/-3.3 cm s(-1) ; mean +/- SEM; P<0.05) and cO2Hb (-7.2+/-2.2 micromol l(-1) ; P<0.05) decreased. At the same time, the VE/Q ratio increased 49+/-14% (P<0.05) with the postural reduction in PETCO2 overestimating the decline in PaCO2 (-4.8+/-0.9 mmHg vs. -3.0+/-1.1 mmHg; P<0.05). When assuming the upright position, the postural decrease in MCA Vmean seems to be explained by the reduction in PETCO2 but the small decrease in PaCO2 makes it unlikely that the postural decrease in MCA Vmean can be accounted for by the cerebral CO2 reactivity alone.