Concentric training is the most commonly utilized strength training protocol, and the vast majority of exercises integrated into our modern resistance training workouts focus on the concentric phase (muscle shortening/contracting) of the movement.
According to a new study, concentric-only strength training may be an efficient way to increase muscle hypertrophy without edema (swelling) and eccentric muscle damage.
To test the hypothesis, researchers gathered 13 untrained men and subjected them to twice-weekly concentric workout sessions for four weeks. The workouts consisted of sets of 8-12 reps to failure of concentric-only unilateral shoulder presses and dumbbell curls. With each session, the researchers increased the training loads. Over the course of the training session, the subjects were also given 500 ml of whole milk to consume.
To determine the effects of the concentric-only training protocol, the researchers assessed soreness, muscle thickness, lean mass, echo intensity, isokinetic strength, and flexed and relaxed arm circumference. These tests were conducted every 72 to 96 hours for the four weeks of the testing period.
After the four weeks, the researchers collected the final data. They found that the concentric-only training protocol did not affect echo intensity, peak torque, or relaxed arm circumference.
However, there were visible changes to muscle thickness, lean mass, and flexed arm circumference before the end of the protocol. The seventh test revealed a 0.2% increase in lean muscle mass, while the eighth and final test revealed a 3.5% increase. Muscle thickness increased by as much as 0.31 centimeters within the four weeks of training.
What this SUGGESTS is that concentric-only strength training programs are suitable for beginner resistance trainees. Not only can they lead to detectable results (as seen via the data above), but the hypertrophy is likely to occur without edema (swelling) and eccentric muscle damage. For those new to resistance training, concentric training is the ideal place to start working out.
However, as a note of caution, there may also be an argument that this study adopted a regimen that was particularly hard and that early gains for anyone is very much determined by genetics, nutrition, and other extenuating circumstances. The NSCA would suggest that a 6-8 week program would be a better period to help facilitate gains. More interesting for the average newbie is the fact that different studies into muscle growth rely on a variety of measures including MRIs, and direct muscle biopsies. In other words, sure, there’s muscle growth, but you have to really look for it to find it.
1. Stock, M.S., Mota, J.A., DeFranco, R.N. et al. “The time course of short-term hypertrophy in the absence of eccentric muscle damage“
Eur J Appl Physiol (2017) 117: 989. https://doi.org/10.1007/s00421-017-3587-z.