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Human skeletal muscle responses to prolonged spaceflight: functional capacity of single slow and fast fibers
Author(s) -
Fitts Robert H,
Romatowski Janell G,
Peters James R,
Trappe Scott,
Gallagher Phillip,
Creer Andrew,
Costill David,
Riley Danny A
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a952-b
Subject(s) - spaceflight , treadmill , fiber , fiber type , muscle fibre , skeletal muscle , chemistry , zoology , medicine , anatomy , biology , physics , astronomy , organic chemistry
Soleus (Sol) and gastrocnemius (Gast) biopsies were obtained preflight and on landing day from 9 crewmembers (45±2 y), averaging 181d aboard the Space Station. Subjects self‐distributed into those performing high (>200 min/wk) treadmill exercise (HT) and low treadmill exercise (<100 min/wk) (LT). For 540 preflight Sol type I fibers, the mean values ± SE were diameter 98 ± 1 (μm), peak force (0.86 ± 0.01 mN), maximal velocity (0.86 ± 0.02 V 0 in fiber lengths (FL)/s), and peak power (14.01 ± 0.47 μN·FL·s −1 ). Following flight, for 458 fibers these parameters declined by 19, 35, 19, and 47 %, respectively. The decline in peak force was due to fiber atrophy as mean relative force (kN/m 2 ) pre (115 ± 1) vs post (114 ± 1) was unaltered. Peak power fell from reduced velocity (19%) and force (33%). Sol type II and Gast type I fibers showed less dramatic declines in size, force and power. HT exercise partially protected type I fibers. The declines in the HT group were fiber diameter (9%), force (23%), and power (34%) compared to 26, 43, and 52 % for these variables in the LT group. The 19% decline in V 0 was the same in both HT and LT crewmembers and contrasts to a 30% increase in V 0 observed following 17 d spaceflight. These data indicate that while the level of treadmill use in space may aid in preserving lower limb muscle mass, modifications to the current exercise prescription are needed to better protect fiber power. Supported by NASA Grant NCC9‐116.