European journal of applied physiology and occupational physiology
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Exposure of juvenile skeletal muscle to a weightless environment reduces growth and satellite cell mitotic activity. However, the effect of a weightless environment on the satellite cell population during muscle repair remains unknown. Muscle injury was induced in rat soleus muscles using the myotoxic snake venom, notexin. ⋯ Hindlimb suspension reduced (P < 0.05) BrdU labeling in uninjured soleus muscles compared to weight-bearing muscles. However, hindlimb suspension did not abolish muscle regeneration because myofibers formed in the injured soleus muscles of hindlimb-suspended rats, and BrdU labeling was equivalent (P > 0.10) on myofiber segments isolated from the soleus muscles of hindlimb-suspended and weightbearing rats following injury. Thus, hindlimb suspension (weightlessness) does not suppress satellite cell mitotic activity in regenerating muscles before myofiber formation, but reduces growth of the newly formed myofibers.
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Eur J Appl Physiol Occup Physiol · Jan 1998
Randomized Controlled Trial Clinical TrialPositive end expiratory pressure as a method for preventing acute mountain sickness.
In order to study the use of positive end expiratory pressure (PEEP) to prevent acute mountain sickness (AMS), 22 subjects were exposed randomly to 8-h hypobaric hypoxia in a hypobaric chamber (4500 m, 589 hPa, 22 degrees C) once being administered 5-cm H2O PEEP and once without. The prevention of AMS by PEEP was evaluated by scoring AMS according to the Lake Louise system (self-report questionnaire and clinical assessment) throughout the experiment with O2 saturation (SO2) and heart rate measurements being made. Arterial blood analyses (partial pressures of arterial O2 and CO2, PaO2, PaCO2, and pH) were made at the end of the exposure. ⋯ Moreover, heart rate increased with PEEP (P < 0.05). In conclusion, this study would suggest that a 5-cm H2O PEEP may help decrease AMS scores at the end of an 8-h exposure to hypoxia in a hypobaric chamber. Such a method could be used to prevent AMS in such experimental conditions without adverse effects.
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Eur J Appl Physiol Occup Physiol · Jan 1998
Back extensor and psoas muscle cross-sectional area, prior physical training, and trunk muscle strength--a longitudinal study in adolescent girls.
The association between physical training, low back extensor (erector spinae plus multifidus muscles) and psoas muscle cross-sectional areas (CSA) and strength characteristics of trunk extension and flexion were studied in adolescent girls. A group of athletes (n = 49) (age range 13.7-16.3 years) consisting of gymnasts, figure skaters and ballet dancers was age-matched with non-athletes (n = 17) who acted as a sedentary control group. The CSA of psoas muscles and multifidus plus erector spinae muscles were measured from lumbar axial images by magnetic resonance imaging. ⋯ There was a significant correlation between muscle CSA and strength parameters, but the force per muscle CSA did not differ significantly between the athletes and the non-athletes. In addition, the athletes showed a better body mass adjusted muscle endurance in trunk flexion (P < 0.05) than the non-athletes. Our study indicated that regular physical training enhances trunk musculature hypertrophy, force and endurance in adolescent girls, and that there is an association between muscle CSA and strength parameters.
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Eur J Appl Physiol Occup Physiol · Jan 1997
Accuracy of pulse oximetry during intense exercise under severe hypoxic conditions.
There is a growing need to measure arterial oxygen saturation with a non-invasive method during heavy exercise under severe hypoxic conditions. Although the accuracy of pulse oximetry has been challenged by several authors, it has not been done under extreme conditions. The purpose of this study was to evaluate the accuracy of a pulse oximeter (Satllite. ⋯ SpO2[corr] and SaO2 were highly correlated (r = 0.93, SEE = 1.81) for low values. During high-intensity constant workload under severe hypoxic conditions, once corrected, pulse oximetry provides an estimate of SaO2 with a mean error of 2%. Thus, the correction previously described for SpO2 values above 75% saturation applies also to SpO2 values in the range of 57-75% during exercise under hypoxic conditions.
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Eur J Appl Physiol Occup Physiol · Jan 1996
Restoration of fluid balance after exercise-induced dehydration: effects of food and fluid intake.
This study investigated the effects of post-exercise rehydration with fluid alone or with a meal plus fluid. Eight healthy volunteers (five men, three women) were dehydrated by a mean of 2.1 (SEM 0.0)% of body mass by intermittent cycle exercise in a warm [34 (SEM 0) degrees C], humid [55 (SEM 1)% relative humidity] environment. Over 60 min beginning 30 min after exercise, the subjects ingested a commercially-available sports drink (21 mmol.l-1 Na+, 3.4 mmol.l-1 K+, 12 mmol.l-1 Cl-) on trials A and B: on trial C a standard meal [63 kJ.kg-1 body mass (53% CHO, 28% fat, 19% protein; 0.118 mmol.kJ-1 Na+, 0.061 mmol.kJ-1 K+)] plus drink (1 mmol.l-1 Na+, 0.4 mmol.l-1 K+, 1 mmol.l-1 Cl-) were consumed. ⋯ This may have been due to the larger quantities of Na+ and K+ ingested with the meal [mean 63 (SEM 4) mmol Na+, 21.3 (SEM 1.3)mmol K+] than with the drink [mean 42(SEM 2)mmol Na+, 6.8 (SEM 0.4)mmol K+]. There was no difference between trials B and C in any of the measured blood parameters, but urinary Na+ and K+ excretion were both higher on trial C and B. These results suggest that post-exercise fluid replacement can be achieved by ingestion of water if consumed in sufficient volume together with a meal providing significant amounts of electrolytes.