A research team from Australian Catholic University, Melbourne recently published (JD Presland et al., Hamstring Strength and architectural adaptations following inertial fl ywheel resistance training. J Sci Med Sport (2020) https://doi.org/10.1016/j.jsams.2020.04.07) an additional piece of information lending more in support to the benefi ts of YoYo methods in general, and the nHANCE driven by Leg Curl in particular.

This research team investigated how the architecture of the hamstring adapted to 6-weeks of YoYo leg curl training using a randomized, stratified training intervention design. Twenty healthy men ndertook 6-weeks of unilateral concentric/eccentric, or “eccentrically biased” (authors defi nition; bilateral concentric/unilateral eccentric) on the #213 YoYoTM Leg Curl training twice weekly (4-6 sets of 6-8 reps). Biceps femoris long head (BFlh) architecture was assessed before, weekly, and subsequent to a 4-week detraining period, using twodimensional ultrasonography.
The participants who trained with eccentric bias showed a robust and significant 14% increase in BFlh fascicle length after 6-weeks training.
This increase in fascicle length was abolished subsequent to 4-weeks detraining. The unilateral training group showed no changes in BFlh fascicle length after the intervention.
The authors concluded that YoYoTM leg curl training performed with an “eccentric bias” led to significant BFlh fascicle lengthening. Interestingly these increases in fascicle length were lost following 4-weeks detraining.
These findings suggest that additional eccentric bias is required to promote fascicle lengthening in the BFlh.
The four graphs below show the fascicle length of the biceps femoris before (pre), during and after (post) the 6-wk training intervention, and after four weeks of detraining for the trained and untrained leg of the unilateral group (top), the untrained and trained leg of the ”ecc bias” group (below).

Editor’s Comment:
Evidently there is an early onset of benefi cial changes in fascicle length of the biceps femoris with 6 weeks training using the #213 YoYo Leg Curl emphasizing eccentric overload. As the training induced increase in fascicle and hence muscle length, is abolished after only 4 weeks detraining, it remains hamstring eccentric overload training should be part of the in-season routine in athletes vulnerable to hamstring strain.
For more information on the above study, contact Ryan G. Timmins at Ryan.
Timmins@acu.edu.au