The primary goals of many resistance training programs are to increase strength and build muscle mass (hypertrophy). The question is, how much intensity is needed to maximize strength gains and hypertrophy while minimizing soreness and associated interruptions to other components of a performance program (eg skill /craft development and game schedules)?
When referencing the percentage of maximum dynamic strength (1RM), 65-85% has been the benchmark in order to improve maximal strength and muscle mass (American College of Sports Medicine et al 2009). However, studies have shown that 30-50% intensity can promote similar gains in muscle mass and strength compared to higher intensities (Lamon, Wallace, Leger, & Russell, 2009; Leger et al., 2006; Mitchell et al., 2012; Ogasawara,Loenneke, Thiebaud, & Abe, 2013; Schoenfeld,Peterson, Ogborn, Contreras, & Sonmez, 2015). This has enormous clinical relevance and application.
The current study investigated the effect of different resistance training intensities with matched volumes on 1RM in order to see the effect on muscle cross-sectional area and muscle strength. The study is unique to other studies investigating a similar effect by matching the volume based on a low intensity (20%) exercise performed to failure and then matching that volume to the higher intensities. The researchers hypothesized that intensities between 40-80%1RM would produce similar hypertrophic responses and that higher intensities (60-80% 1RM) would have greater effects on muscle strength when compared to lower intensities (20-40%1RM).
Lasevicius et al 2018 employed 30 healthy young men to participate in a 12-week resistance training program. A within-subject design was used in which one leg and arm were trained at 20% for all participants, and the contralateral limb was randomly assigned to one of the three possible conditions (40, 60, or 80% 1RM). The participants performed three sets at 20% with each set performed to failure of a 45 degree single-leg leg press and bicep curl. Volume was calculated (sets x reps x load) from the 20% and used to match the volume at the other intensities.
The main findings of this current study were:
- All intensities increased the cross-sectional area of the elbow flexors and Vastus Lateralis
- All intensities increased the 1RM of both the 45 degree single-leg leg press and the bicep curl. The magnitude of increases in the cross-sectional area and maximal strength were greater in the 80% group than 20% but still significant at lower intensities.
These findings suggest that volume, and not solely intensity, plays an important role in training for strength and muscle mass gains. This is important for practitioners dealing with athletes in rehabilitation where higher intensities may be precluded by pain and / or joint or tendon pathology. It is also relevant when game schedules require a different training intensity in the gym but long-term strength and muscle mass goals remain important.
The mechanism behind these observations is likely the higher recruitment of muscle fibers when a lower-intensity exercise is performed to failure. Importantly, it provides additional prescriptive options, beyond the American College of Sports Medicine recommendation of 65-85% training intensity for increasing muscle mass, when clinicians seek to juggle athlete and team needs in the short and long term.
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