Hypertrophy Science: Volume, Repetition Duration, Rest Intervals, Contraction Types and Contraction Speed


One meta-analysis suggests that multiple-sets (3-6) per exercise (per session) is associated with 40% greater hypertrophy-related Effect Size than 1 set, in both trained and untrained subjects (1). However there is one critique of that meta-analysis (2), with the authors suggesting that only one set per exercise to failure is necessary (3).

Another meta-analysis supports the notion that higher-volume, multiple-set protocols is superior over single set protocols for hypertrophy, for untrained subjects, with the difference becoming more evident as progression occurs (4).

In a recent study done in previously trained males, training volume was a significant contributor to strength and hypertrophy adaptations, which occur independent of specific repetition ranges (5).

After progressive overload, this suggests that volume is the most important factor for the hypertrophic response.

A systematic review and meta-analysis also reveals a dose-response relationship between weekly resistance training volume and increases in muscle mass. Hypertrophy progressively increases from 1-4 weekly sets per muscle group per week, to 5-9 weekly sets per muscle group per week, and then 10+ sets per muscle group per week (6). There was insufficient data to establish where the maximum threshold lies.

Contraction Types

There are different types of muscle contraction, the concentric or positive motion; the eccentric or negative; isometric. There is a difference in muscle-fiber recruitment and activation in each contraction and thus a different in force production.

Muscles achieve higher absolute forces when contracting eccentrically (7,8,9). Eccentric strength is approximately 20–50% greater than the concentric strength (10), even predicted to be up to 64% greater (11), and stimulates greater adaptations (12) and appears to be more effective at increasing muscle mass than concentric training.

Eccentric exercise preferentially recruit fast twitch muscle fibers (13,14,15,16) and perhaps recruitment of previously inactive MUs (14,17). This results in an increased mechanical tension in type II fibers, which have the greatest potential for muscle growth (13,18,19,20). A single bout of eccentric exercise results also in a greater increase in IGF-I mRNA expression than a single bout of concentric exercise (21).

Heavy negatives, assisted negatives, or supramaximal eccentric actions with a weight greater than concentric 1RM are some techniques that can applied for this goal. Since a muscle is not fully fatigued during concentric training (22), the use of heavy negatives is recommended. There’s also the use of a flywheel or isokinetic equipment to overload the ECC phase (23), but in this case the contractions can be below the concentric 1RM, but at the end of the set there’s more total volume/load for the eccentric actions.

Isometric contractions consists in holding a static contraction, the muscle doesn’t shorten or lengthen. Isometric muscle actions can also induce hypertrophy (24,25) and should be included in a training program.

Contraction speed

Faster concentric repetitions (1s vs. 3s) are more beneficial for hypertrophy (26). Faster/heavier eccentric repetitions leads to greater hypertrophy in type II fibers, and strength gains than slower/lighter eccentric repetitions (27). Faster speed eccentric contractions release more growth factors, more satellite cells, and greater protein synthesis than slow speed eccentric contractions (28,29). A 2-3 second tempo is hypothesized to be ideal for maximizing a hypertrophic response (28).

Very slow velocities (i.e., superslow training) is suboptimal for strength and hypertrophy (30,31,32). There are some proponents of superslow training, and some studies have been published in nonpeer-reviewed articles. For example a study by Westcott (33) claimed superslow to be slighter superior for strength than traditional training (for elderly individuals), although the results were not statistically significant, and it wasn’t peer-reviewed.

The majority of the literature indicates superslow training to be suboptimal for general populations. Special populations may benefit from this, injured individuals or elderly suffering from osteoporosis, as it was developed for anyway.

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