Improvement in muscle strength with low-load isotonic training depends on fascicle length but not joint angle.
BACKGROUND
In this study we investigate whether low-load isotonic training will elicit greater improvement in muscle strength at the same fascicle length, rather than at the same joint angle.


METHODS
Sixteen healthy men (24.1 ± 2.5 years of age) were randomly divided into intervention and control groups. Pre- and posttraining maximum isometric and isokinetic strengths and fascicle lengths of the medial gastrocnemius muscle were measured. Isotonic resistance training at 15 ° to 30 ° ankle plantarflexion at low intensity was conducted for 4 weeks.


RESULTS
The maximum isometric and isokinetic strength of the intervention group increased significantly only at 15 ° dorsiflexion and 8 ° to 12 ° dorsiflexion. Fascicle length during maximum voluntary contraction at 15 ° dorsiflexion to 0 ° was similar to fascicle length under training conditions.


CONCLUSIONS
It is possible that the improvement in muscle strength with low-load training depends on fascicle length rather than joint angle. Muscle Nerve 57: 83-89, 2018.
Rehabilitation Unit, Kyoto University Hospital, 54, Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
Hiroki
H
Tanaka
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Tome
T
Ikezoe
Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan.
Masatoshi
M
Nakamura
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Ko
K
Yanase
Rehabilitation Group, Department of Medical Technique, Nagoya University Hospital, Nagoya, Japan.
Kosuke
K
Fujita
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Yoshiki
Y
Motomura
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Ken
K
Kusano
Department of Rehabilitation, Sapporo Tokushukai Hospital, Hokkaido, Japan.
Kojiro
K
Araki
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Jun
J
Umehara
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Junya
J
Saeki
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Katsuyuki
K
Morishita
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Noriaki
N
Ichihashi
D000328:Adult; D000843:Ankle Joint / Q000033:anatomy & histology / Q000502:physiology; D015444:Exercise; D064368:Healthy Volunteers; D006801:Humans; D007551:Isotonic Contraction; D007596:Joints / Q000033:anatomy & histology* / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D010806:Physical Education and Training / Q000379:methods*; D055815:Young Adult
low-load; plantarflexion; specificity of training; training adaptation; triceps surae; ultrasound