Effects of high-intensity swimming training on GLUT-4 and glucose transport activity in rat skeletal muscle.
This study was performed to assess the effects of short-term, extremely high-intensity intermittent exercise training on the GLUT-4 content of rat skeletal muscle. Three- to four-week-old male Sprague-Dawley rats with an initial body weight ranging from 45 to 55 g were used for this study. These rats were randomly assigned to an 8-day period of high-intensity intermittent exercise training (HIT), relatively high-intensity intermittent prolonged exercise training (RHT), or low-intensity prolonged exercise training (LIT). Age-matched sedentary rats were used as a control. In the HIT group, the rats repeated fourteen 20-s swimming bouts with a weight equivalent to 14, 15, and 16% of body weight for the first 2, the next 4, and the last 2 days, respectively. Between exercise bouts, a 10-s pause was allowed. RHT consisted of five 17-min swimming bouts with a 3-min rest between bouts. During the first bout, the rat swam without weight, whereas during the following four bouts, the rat was attached to a weight equivalent to 4 and 5% of its body weight for the first 5 days and the following 3 days, respectively. Rats in the LIT group swam 6 h/day for 8 days in two 3-h bouts separated by 45 min of rest. In the first experiment, the HIT, LIT, and control rats were compared. GLUT-4 content in the epitrochlearis muscle in the HIT and LIT groups after training was significantly higher than that in the control rats by 83 and 91%, respectively. Furthermore, glucose transport activity, stimulated maximally by both insulin (2 mU/ml) (HIT: 48%, LIT: 75%) and contractions (25 10-s tetani) (HIT: 55%, LIT: 69%), was higher in the training groups than in the control rats. However, no significant differences in GLUT-4 content or in maximal glucose transport activity in response to both insulin and contractions were observed between the two training groups. The second experiment demonstrated that GLUT-4 content after HIT did not differ from that after RHT (66% higher in trained rats than in control). In conclusion, the present investigation demonstrated that 8 days of HIT lasting only 280 s elevated both GLUT-4 content and maximal glucose transport activity in rat skeletal muscle to a level similar to that attained after LIT, which has been considered a tool to increase GLUT-4 content maximally.
Terada
S
S
Department of Physiology and Biomechanics, National Institute of Fitness and Sports, Kanoya City, Kagoshima 891-2393, Japan.
Yokozeki
T
T
Kawanaka
K
K
Ogawa
K
K
Higuchi
M
M
Ezaki
O
O
Tabata
I
I
D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D004558:Electric Stimulation; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013550:Swimming / Q000502:physiology*
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D006003:Glycogen; D003847:Deoxyglucose; D002950:Citrate (si)-Synthase; D005947:Glucose