Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones

Abstract

Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate the "strength-endurance continuum". Subjects were divided into four groups: a low repetition group (Low Rep, n = 9) performing 3-5 repetitions maximum (RM) for four sets of each exercise with 3 min rest between sets and exercises, an intermediate repetition group (Int Rep, n = 11) performing 9-11 RM for three sets with 2 min rest, a high repetition group (High Rep, n = 7) performing 20-28 RM for two sets with 1 min rest, and a non-exercising control group (Con, n = 5). Three exercises (leg press, squat, and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g., maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion) were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization. Maximal strength improved significantly more for the Low Rep group compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion significantly increased at the end of the study for only the High Rep group. All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups. However, the percentage of type IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups. These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a significant increase in MHCIIa. No significant changes in fiber-type composition were found in the control samples. Although all three training regimens resulted in similar fiber-type transformations (IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects. Overall, however, these data demonstrate that both physical performance and the associated physiological adaptations are linked to the intensity and number of repetitions performed, and thus lend support to the "strength-endurance continuum".

High‐Intensity Resistance Training with Insufficient Recovery Time Between Bouts Induce Atrophy and Alterations in Myosin Heavy Chain Content in Rat Skeletal Muscle

“…However, the reduction in Type IID fiber frequency in the plantaris SW portion in Tr was not associated with a change in MHCIId content (P > 0.05). Contrary to previous resistance-training studies that show a MHCIIb-to-MHCIIa transition within the fast fiber population (Campos et al, 2002;Harber et al, 2004), we observed a transition of MHCI and MHCIIa toward MHCIIb isoform content in plantaris muscle during high-intensity/volume training with insufficient recovery time between bouts. This might indicate that the activity patterns of fiber Types I and IIA (MHCI and MHCIIa isoforms), more frequent in plantaris DR portion, which have relatively high oxidative potential, possibly were more susceptible to oxidative damage by reactive oxygen species during high volume exercise in rats plantaris muscle.…”

“…Eight histological sections (12 lm thick) were collected from each whole muscle sample and placed in a solution (0.5 mL) containing glycerol 10% (w/vol), 2-mercaptoethanol 5% (vol/vol), and sodium dodecylsulfate (SDS) 2.3% (w/ vol) in a Tris/HCl buffer 0.9% (pH 6.8; w/vol). The final solution was shaken for 1 min and heated for 10 min at 60 C (Campos et al, 2002). Portions (20 lL) of the extracts were submitted to electrophoresis reaction (SDS-PAGE 8%) using a 4% stacking gel, for 26 hr at 180 V, where the maximum current was limited to 13 mA.…”

“…In addition, high resistance training has been shown to promote muscle fiber-type modulation and MHC isoform changes (Campos et al, 2002;Ratamess et al, Values are means AE SD. Non-trained (Co, N ¼ 9) and trained (Tr, N ¼ 9) groups.…”

“…It is generally accepted that skeletal muscle can adapt to progressive physical training via both a quantitative mechanism, based on changes in muscle mass and fiber size, and a qualitative mechanism, based on changes in fiber type and MHC content (Schiaffino and Reggiani, 1996). In this context, histochemical and biochemical studies have reported that resistance training promotes significant alteration in MHC content, enhancing physical performance (Sharman et al, 2001;Campos et al, 2002;Harber et al, 2004).…”

Benefits of intensive resistance training in patients with chronic polymyositis or dermatomyositis

“…Definitions of different exercise protocols for healthy individuals have previously been described in the literature as follows: low repetition/high intensity varying between 3-6 and 6 -8 repetitions, moderate repetition/moderate intensity varying between 9 -11, 15-20, and 30 -40 repetitions, and high repetition/low intensity varying between 20 -28, 30 -40, and 100 -150 repetitions (47)(48)(49). According to these definitions, our exercise program could be defined as intermediate with more strength-training properties than endurance training.…”