Does eccentric overload training enhance muscle growth?

Many lifters wonder about the utility of eccentric training. Since the concentric phase is where you should fail the rep, is the eccentric phase really that useful? Isn't it under-loaded relative to the concentric phase? That logic leads to the concept of accentuated eccentrics, or eccentric overload training. However, research suggests that normal, traditional training already exposes the muscle to sufficient eccentric stimulus.

A recent study by Yue et al is the newest addition to this body of research. The researchers compared the effects of traditional squats versus accentuated eccentric loading on muscle growth. One group of subjects performed traditional squats, while another group used weight releasers on 2 reps per set, and a third group used weight releasers on all 6 reps. The results showed that eccentric overload training led to greater muscle growth.

However, previous research was less convincing. A study by Douglas et al found that trained rugby players completed 12 weeks of squats, with one group performing accentuated eccentrics about 20% heavier than the concentric load. The eccentric group showed early gains in strength and sprint speed, but quadriceps muscle thickness did not increase in either group.

Mechanistically, the increased load for the eccentric phase may fatigue the lifter more, reducing the total number of repetitions performed. However, even with accentuated eccentrics, the practicality problem remains. Performing them safely requires specialized equipment and a spotter. Until this technology becomes more widespread, accentuated eccentrics may not be a practical solution for most lifters.

In contrast, simpler methods such as using a bit of body English to assist with the concentric portion after a slow, deliberate lowering, or performing eccentrics unilaterally and concentrics with assistance, can capture the essence of eccentric overload without the need for specialized equipment or spotters. This line of research highlights the importance of weighing theoretical rationale against actual evidence.