Resistance training frequency: strength and myosin heavy chain responses to two and three bouts per week.
Seventeen subjects performed resistance training of the leg extensor and flexor muscle groups two (2/wk) or three (3/wk) times per week. Changes in the relative myosin heavy chain (MHC) isoform contents (I, IIa and IIx) of the vastus lateralis and isometric, isokinetic and squat-lift one-repetition maximum (1 RM) strength were compared between conditions after both a common training period (6 weeks) and number of training sessions (18). After 6 weeks and 18 sessions (9 weeks for the 2/wk group), increments in 1RM strength for the 3/wk and 2/wk groups were similar [effect size (ES) differences approximately 0.3, 3/wk > 2/wk], whereas the 2/wk group presented greater isokinetic (ES differences = 0.3-1.2) and isometric (ES differences approximately 0.7) strength increases than the 3/wk condition. A significant (P < 0.05) increase in MHC IIa percentage was evident for the 2/wk group after 18 sessions. Both training groups exhibited a trend towards a reduction in the relative MHC IIx and an increase in MHC IIa contents (ES range = 0.5-1.24). However, correlations between changes in the strength and MHC profiles were weak (r2: 0.0-0.5). Thus, isometric and isokinetic strength responses to variations in training frequency differed from 1RM strength responses, and changes in strength were not strongly related to alterations in relative MHC content.
Department of Human Movement Studies, The University of Queensland, Brisbane, Australia.
T J
TJ
Carroll
P J
PJ
Abernethy
P A
PA
Logan
M
M
Barber
M T
MT
McEniery
D000293:Adolescent; D000328:Adult; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D010809:Physical Fitness / Q000502:physiology*; D014891:Weight Lifting / Q000502:physiology*
D018995:Myosin Heavy Chains