Low-volume muscle endurance training prevents decrease in muscle oxidative and endurance function during 21-day forearm immobilization.
OBJECTIVE
To examine the effects of low-volume muscle endurance training on muscle oxidative capacity, endurance and strength of the forearm muscle during 21-day forearm immobilization (IMM-21d).


METHODS
The non-dominant arm (n = 15) was immobilized for 21 days with a cast and assigned to an immobilization-only group (Imm-group; n = 7) or an immobilization with training group (Imm+Tr-group; n = 8). Training comprised dynamic handgrip exercise at 30% of pre-intervention maximal voluntary contraction (MVC) at 1 Hz until exhaustion, twice a week during the immobilization period. The duration of each exercise session was 51.7 +/- 3.4 s (mean +/- SE). Muscle oxidative capacity was evaluated by the time constant for phosphocreatine recovery (tau(off)PCr) after a submaximal handgrip exercise using (31)phosphorus-magnetic resonance spectroscopy. An endurance test was performed at 30% of pre-intervention MVC, at 1 Hz, until exhaustion.


RESULTS
tau(off)PCr was significantly prolonged in the Imm-group after 21 days (42.0 +/- 2.8 and 64.2 +/- 5.1 s, pre- and post-intervention respectively; P < 0.01) but did not change for the Imm+Tr-group (50.3 +/- 3.0 and 48.8 +/- 5.0 s, ns). Endurance decreased significantly for the Imm-group (55.1 +/- 5.1 and 44.7 +/- 4.6 s, P < 0.05) but did not change for the Imm+Tr-group (47.9 +/- 3.0 and 51.7 +/- 4.0 s, ns). MVC decreased similarly in both groups (P < 0.01).


CONCLUSIONS
Twice-weekly muscle endurance training sessions, each lasting approx. 50 s, effectively prevented a decrease in muscle oxidative capacity and endurance; however, there was no effect on MVC decline with IMM-21d.
Homma
T
T
Department of Sports Sciences, Japan Institute of Sports Sciences, Tokyo, Japan. homma.toshiyuki@jiss.naash.go.jp
Hamaoka
T
T
Murase
N
N
Osada
T
T
Murakami
M
M
Kurosawa
Y
Y
Kitahara
A
A
Ichimura
S
S
Yashiro
K
K
Katsumura
T
T
D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005542:Forearm / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007103:Immobilization / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult