Physiological stimuli necessary for muscle hypertrophy

Abstract

This paper reviews the existing literature about muscle hypertrophy resulting from various types of training to document the significance of mechanical and metabolic stresses, and to challenge the conventional ideas of achieving hypertrophy that exclusively rely on highload resistance training. Low-load resistance training can induce comparable hypertrophy to that of high-load resistance training when each bout or set is performed until lifting failure. This is attributable to the greater exercise volume and metabolic stress achieved with low-load exercise at lifting failure, which, however, results in a prolonged exercise bout. Endurance exercises (walking and cycling) at moderate intensity are also capable of eliciting muscle hypertrophy, but at much slower rates (months rather than weeks) in limited muscle or age groups. Blood flow restriction (BFR) in working muscles, however, accelerates the development of metabolic fatigue, alleviating the time consuming issue associated with low-load or endurance training. These alternative training methods, however, cannot completely replace conventional high-load resistance training, which provides superior strength gain as well as performance improvement even for trained individuals. The alternative approaches, therefore, may be considered for those who are less enthusiastic or under certain medical conditions, or who have limited or no access to proper equipment. However, people should be aware that low-load resistance training or endurance training entails substantial effort and/or discomfort at lifting failure or with BFR. Understanding the advantages and disadvantages of each method will help in assigning the most suitable training program for each client's goals and needs.

Can blood flow restriction augment muscle activation during high‐load training?

“…However, the cuff remained inflated because it has previously been shown that the restoration of phosphocreatine (i.e. clearance of inorganic phosphate) occurs immediately upon deflation of the restrictive stimulus (Suga et al, 2012), and thus deflating the cuff would have allowed for the clearance of metabolites and recovery from fatigue (Ozaki et al, 2015(Ozaki et al, , 2016.…”

Effect of Combined Increased Physical Activity and Walking with Blood Flow Restriction on Leg Muscle Thickness in Older Adults

“…The application of BFR during exercise produces greater and/or faster metabolic fatigue, which would induce greater and/or faster muscle growth 19) . For example, our previous study showed that 20 min of a BFR-walk, 4 days per wk for 10 wk, increased thigh muscle CSA, whereas normal walking did not 21) .…”

“…Muscle hypertrophic adaptations mainly result from exposure to both mechanical and metabolic stresses 19) .…”

“…Metabolic stress is accumulated by blood flow restriction (BFR) in working muscles even during walking, resulting in an enhanced hypertrophic effect with walking 19) . For example, our studies showed that 20 min of a BFR walk, 4-5 days per wk for 6-10 wk, increased thigh muscle size and strength, whereas these adaptations were not observed after a normal walking program in older adults 20) 21) .…”

Strategies for maximizing power and strength gains in isoinertial resistance training: Implications for competitive athletes

“…Projectile motions are important to minimize the deceleration duration, particularly when undergoing Pmax or in detail by Ozaki et al [2015]) 73) . Hence, we suggest that early training sets aim for maximum power output of the given load, followed by fatigue-challenge sets later on.…”