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Life in Space for Life on Earth, ESA, Triest, 2010;

Differential atrophy of the postero-lateral hip and thigh musculature during 60-days bed-rest and the effect of two different countermeasure exercises

Jahr: 2010

Miokovic T, Belavy D, Armbrecht G, Felsenberg D
Charité Universitätsmedizin Berlin, GERMANY

Abstract

Objectives:
Data from previous bed-rest studies have demonstrated that the muscle groups of the thigh most susceptible to atrophy during prolonged inactivity include the hamstrings and the vastii. Limited information is available on the response of hip musculature to prolonged inactivity. As the muscles of the hip and thigh act as synergists, it is important to evaluate them together when considering the effects of bed-rest and countermeasure exercises.

Methods:
24 male subjects underwent 60-days of 6° head-down tilt bed-rest and performed resistive vibration exercise (RVE; n=7), resistive exercise alone (RE; n=8) or no exercise (CTR; n=9) as part of the 2nd Berlin BedRest Study (BBR2-2). Countermeasure exercises included double leg squats, double and single leg calf raises and back-lift exercise manoeuvres, performed 3-days a week, with 5 to 6 minutes of actual loading time (excluding rest periods) each session.
Muscle volumes of hip and thigh musculature were measured using axial magnetic resonance images collected prior to bed-rest, mid-bed-rest (day 27 or 28) and end-bed-rest (day 55 or 56). Analysis of CTR-group data examined differential atrophy of the hip and thigh musculature using an exponential decay model for percentage change in muscle volume. Effects of countermeasures were then examined with linear-mixed effects model for muscle volume data.

Results:
After 60 days bed-rest, the rates of muscle volume loss compared to baseline, differed between muscles (F=58.8, p<.0001; CTR group only), with the fastest losses seen in the semimembranosus and biceps femoris long head, followed by the gluteus minimus, vastii, upper gluteus maximus, adductor magnus, semitendinosus, sartorious, gluteus medius and biceps femoris short head (p= <.0001-.018). Non-significant rates of muscle volume change were observed in the adductor longus, lower gluteus maximus, gracilis, rectus femoris and adductor brevis (p all >.06).
The countermeasures strongly reduced atrophy in the knee extensors (F>4.5, p< 0.0023; vastii: CTR:-16%, RE:-2%, RVE:-4%; rectus femoris: CTR:-6.5%, RE:-2.8%, RVE:+6.8%; all percentages given are change between baseline and end-bed rest) and the mono-articular hip extensors (F>3.4, p<.0125; lower gluteus maximus: CTR:-6%, RE:+8%, RVE:+7%; adductor magnus: CTR:-10%, RE:-2%, RVE:-3%) but with less effect on the hamstrings (F>5.4, p<.0006; biceps femoris long head: CTR:-18%, RE:-13%, RVE:-13%; semimembranosus: CTR:-18%, RE:-13%, RVE:-15%). Only in the adductor brevis, adductor longus and rectus femoris muscle groups was there evidence (F>4.1, p<.0228) of a different effect in the two countermeasure groups, with volume of these muscles increasing in the RVE-group and decreasing in the RE-group.

Conclusions:
Short duration high-load exercise performed 3-days a week during bed-rest can reduce muscle atrophy. Combined hip and knee extension, designed to target the postural muscles most affected during bed-rest, was more effective in reducing atrophy of the knee extensors and mono-articular hip extensors than the hamstrings. Resistive whole body vibration had an additional effect in reducing volume loss of certain muscles of the posterolateral hip and thigh. Recommendations for countermeasure exercise prescription will be discussed.

Schlagworte: Galileo Space, Counter Measure, BBR 2
GID: 2294; Letzte Änderung: 18.06.2010
Weitere Informationen: Original Article