To explore the hypothesis that lower body muscle mass might be associated with orthostatic intolerance, 18 healthy volunteers (18-48 yrs, 10 ♂, 8 ♀) underwent graded lower body negative pressure (LBNP) consisting of six, 5-minute stages of suction up to 60 mmHg in 10mmHg increments. Leg muscle mass was assessed by dual energy X-ray absorptiometry. All subjects received standard intravenous hydration for 12-16 hours prior to the study. Six men and 4 women completed each stage of LBNP. Four men and 4 women developed pre-syncopal symptoms, including marked bradycardia, at LBNP levels of 30 mmHg (n=2; 1 ♂, 1 ♀), 40 mmHg (n=2; 1 ♂, 1 female;), and 50 mmHg (n=4; 2 ♂, 2 female;). The pre-syncopal subjects had leg muscle masses ranging from 19.5 kg to 25.2 kg in men (SEM=1.04), and 11.7 kg to 16.6 kg in women (SEM=1.04). In subjects that completed all stages of LBNP, leg muscle mass ranged from 17.5 kg to 24.1 kg in men (SEM=1.04), and 10.4 kg to 18.0 kg in women (SEM =1.61). These data suggest that leg muscle mass is not a critical determinant of LBNP tolerance in otherwise healthy men and women.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology