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.
Carroll
T J
TJ
Department of Human Movement Studies, The University of Queensland, Brisbane, Australia.
Abernethy
P J
PJ
Logan
P A
PA
Barber
M
M
McEniery
M T
MT
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