Effect of starvation on work capacity and voluntary skeletal muscle function in man

CORP: Measurement of upper and lower limb muscle strength and voluntary activation

Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.

Effect of Ramadan observance on maximal muscular performance of trained men

OBJECTIVE

To assess the influence of Ramadan fasting on maximal performance of moderately trained young men using various tests of muscle performance.

DESIGN

Comparison of Ramadan fasting (n = 10) versus control group (n = 10) over 3 test sessions, before Ramadan (B), at the end of the first week of Ramadan (R-1), and during the fourth week of Ramadan (R-4).

SETTING

At each 2-day test session, 4 tests were performed in the same order: measurement of vertical jump height (VJH) and a force-velocity test using the arms on day 1, and measurement of handgrip force (HGF), and a force-velocity test using the legs on day 2.

PARTICIPANTS

Twenty trained men.

MAIN OUTCOME MEASURES

Maximal power of the arms and of the legs (force-velocity testing), vertical jump performance, HGF, anthropometric data, dietary intake, hemoglobin, and hematocrit.

RESULTS

Two-way analyses of variance (group × time) showed Ramadan fasters with decreased maximal anaerobic power of the arms (Wmax-A) and legs (Wmax-L) at R-1, with a partial return of arm data to initial values at R-4. Vertical jump height and HGF remained unchanged throughout. Other changes in Ramadan observers were a decreased energy intake and a decrease of plasma volume at R-1.

CONCLUSIONS

These results suggest that Ramadan observance initially had detrimental effects on Wmax-A, and Wmax-L, with a tendency to recovery by week 4 of Ramadan. Reductions of total energy intake and intramuscular glycogen may contribute to the reduced Wmax-A and Wmax-L during Ramadan fasting.

Accelerated postoperative recovery programme after colonic resection improves physical performance, pulmonary function and body composition

BACKGROUND

Postoperative organ dysfunction contributes to morbidity, hospital stay and convalescence. Multimodal rehabilitation with epidural analgesia, early oral feeding, mobilization and laxative use after colonic resection has reduced ileus and hospital stay.

METHODS

Fourteen patients receiving conventional care (group 1) and 14 patients who had multimodal rehabilitation (group 2) were studied before and 8 days after colonic resection. Outcome measures included postoperative mobilization, body composition by whole-body dual X-ray absorptiometry, cardiovascular response to treadmill exercise, pulmonary function and nocturnal oxygen saturation.

RESULTS

Defaecation occurred earlier (median day 1 versus day 4) and hospital stay was shorter (median 2 versus 12 days) in patients who had multimodal treatment. Lean body and fat mass decreased in group 1 but not in group 2. Exercise performance decreased by 44 per cent in group 1 but was unchanged in group 2. A postoperative increase in heart rate (HR) response to exercise was avoided in group 2. Pulmonary function decreased in group 1 but not in group 2. There was less nocturnal postoperative hypoxaemia in group 2. Cardiac demand-supply (HR/oxygen saturation ratio) increased in group 1 but not in group 2.

CONCLUSION

Multimodal rehabilitation prevents reduction in lean body mass, pulmonary function, oxygenation and cardiovascular response to exercise after colonic surgery.

Postoperative fatigue

Uncomplicated major surgery is followed by a pronounced increased feeling of fatigue extending throughout the first month in about one-third of patients. Postoperative fatigue correlates with the degree of surgical trauma but is not related to duration of general anesthesia and surgery or to preoperative nutritional status, age, or sex. Fatigue also correlates with postoperative deterioration in nutritional parameters and impaired adaptability of heart rate during exercise. Furthermore, a postoperative decrease in muscle force and endurance is related to postoperative fatigue, whereas psychological factors are of minor importance. These findings suggest postoperative fatigue to be mediated by the endocrine-metabolic response to surgery, impaired nutritional intake, or immobilization, but the relative role of these factors remains to be established. Until then, therapeutic measures against the development of postoperative fatigue should aim at reducing the surgical stress response, effective treatment of pain to facilitate mobilization, and exercise to increase postoperative nutritional intake.