Myosin heavy chain (MHC) isoform expression changes with physical training. This may be one of the mechanisms for muscular adaptation to exercise. We aimed to investigate the effects of different strength-training protocols on MHC isoform expression, bearing in mind that α- MHCslow(newly identified MHC isoform) mRNA may be upregulated in response to training. Twelve volunteers performed a 6-wk strength training with maximum contractions (Max group), and another 12 of similar age performed combination training of maximum contractions and ballistic and stretch-shortening movements (Combi group). Muscle samples were taken from triceps brachii before and after training. MHC isoform composition was determined by SDS-PAGE silver staining, and mRNA levels of MHC isoforms were determined by RT-PCR. In Max group, there was an increase in MHC2A (49.4 to 66.7%, P< 0.01) and a decrease in MHC2X (33.4 to 19.5%, P < 0.01) after training, although there was no significant change in MHCslow. In Combi group, there was also an increase in MHC2A (47.7 to 62.7%, P < 0.05) and a decrease in MHCslow (18.2 to 9.2%, P < 0.05) but no significant change in MHC2X. An upregulation of α-MHCslow mRNA was, therefore, found in both groups as a result of training. The strength training with maximum contractions led to a shift in MHC isoform composition from 2X to 2A, whereas the combined strength training produced an MHC isoform composition shift from slow to 2A.

The aim of this study was to compare the effects of singleset and multiple-set strength training in women. Twentyseven women (aged 20-40 years) with basic experience in strength training were randomly allocated to either a singleset group (n ϭ 9), a 3-set group (n ϭ 9), or a nontraining control group (n ϭ 9). Both training groups underwent a whole-body strengthening program, exercising 2 days a week for 6 weeks. Exercises included bilateral leg extension, bilateral leg curl, abdominal crunch, seated hip adduction/ abduction, seated bench press, and lateral pull-down. The single-set group's program consisted of only 1 set of 6-9 repetitions until failure, whereas the multiple-set group trained with 3 sets of 6-9 repetitions until failure (rest interval between sets, 2 minutes). Two times before and 3 days after termination of the training program, subjects were tested for their 1 repetition maximum strength on the bilateral leg extension and the seated bench press machine. Data were analyzed using a repeated-measures analysis of variance, Scheffé tests, t-tests, and calculation of effect sizes. Both training groups made significant strength improvements in leg extension (multiple-set group, 15%; single-set group, 6%; p 0.05). However, in the seated bench press only the 3-set group showed a significant increase in maximal strength (10%). Calculation of effect sizes and percentage gains revealed higher strength gains in the multiple-set group. No significant differences were found in the control group. These findings suggest superior strength gains occurred following 3-set strength training compared with single-set strength training in women with basic experience in resistance training.Reference Data: Schlumberger, A., J. Stec, and D. Schmidtbleicher. Single-vs. multiple-set strength training in women. J. Strength Cond. Res. 15(3):284-289. 2001.