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Eur J Appl Physiol. 2018 Jul;118(7):1339-1347. doi: 10.1007/s00421-018-3866-3. Epub 2018 Apr 20.

Effects of training intensity in electromyostimulation on human skeletal muscle.

Author information

1
Institute of Health and Sports Science & Medicine, Juntendo University, 1-1 Hirakagakuendai, Inzai, Chiba, 270-1695, Japan. natsumetoshiharu@gmail.com.
2
Graduate School of Health and Sports Science, Juntendo University, 1-1 Hirakagakuendai, Inzai, Chiba, 270-1695, Japan.
3
School of Medicine, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
4
Department of General Medicine, Mito Medical Center, Tsukuba University Hospital, 3-2-7 Miyamachi, Mito, Ibaraki, 310-0015, Japan.
5
Institute of Health and Sports Science & Medicine, Juntendo University, 1-1 Hirakagakuendai, Inzai, Chiba, 270-1695, Japan.

Abstract

PURPOSE:

High-intensity neuromuscular electrical stimulation (NMES) training can induce muscle hypertrophy at the whole muscle and muscle fiber levels. However, whether low-intensity NMES training has a similar result is unknown. This study aimed to investigate whether low-intensity NMES training could elicit muscle hypertrophy at the whole muscle and muscle fiber levels in the human skeletal muscle.

METHODS:

Eight untrained young males were subjected to 18 min of unilateral NMES training for 8 weeks. One leg received NMES at maximal tolerable intensity (HIGH); the other leg received NMES at an intensity half of that in the HIGH condition (LOW). Quadriceps muscle thickness (MT), muscle fiber cross-sectional area (CSA), and knee extension strength were measured before and after the training period.

RESULTS:

The average training intensity throughout the intervention period in the HIGH and LOW conditions were 62.5 ± 4.6% maximal voluntary contraction (MVC) and 32.6 ± 2.6% MVC, respectively. MT, CSA, and muscle strength increased in both exercise conditions (p < 0.05); however, training effects in the LOW condition were lower than those in the HIGH condition (p < 0.05). The average training intensity showed a positive correlation with percent changes in muscle strength (r = 0.797, p = 0.001), MT (r = 0.876, p = 0.001), type I fiber CSA (r = 0.730, p = 0.01), and type II fiber CSA (r = 0.899, p = 0.001).

CONCLUSIONS:

Low-intensity NMES could increase MT, muscle fiber CSA, and muscle strength in healthy human skeletal muscles. However, the magnitude of increase is lower in low-intensity than in high-intensity NMES training.

KEYWORDS:

Maximal voluntary contraction; Muscle fiber; Muscle thickness; Neuromuscular electrical stimulation

PMID:
29679248
DOI:
10.1007/s00421-018-3866-3
[Indexed for MEDLINE]

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