Visualization Boosts Strength Gains - 'Mental Effort' Boosts Biceps Strength Gains on Low Intensity Workout by 20%!

The study setup looked sign. different.

You will have heard or read about resistance training experts and bodybuilders alike bragging about "focus" and "visualization" being keys to maximal strength and muscle gains. Now, a recent study from the Capital University of Physical Education and Sports in China, the Lerner Research Institute, the Kessler Foundation and the New Jersey Medical School in the US provides what I would deem the first decently convincing evidence that "mental effort" is a previously overlooked counterpart to "physical effort" when it comes to strength training.

As the authors point out, "[h]istorically, most strength training programs have emphasized that, for maximum strength gain, training should be conducted at load intensities that are at or near the maximum level and last long enough for all motor units/muscle fibers in a muscle or muscle group to be fully activated" (Jiang 2017). As a SuppVersity reader, you will yet be aware that more recently multiple studies have shown that neural adaptations can result in significant strength gain, as well.
Unfortunately, previous studies like Yue & Coke (1992) or Ranganathan et al. (2004) investigated the effects of "mental power" on "muscle power" only in the fingers. Jiang's current pilot study is, as far as I know, thus the first study to test te hypothesis that "mental training" will augment the biceps strength gains of healthy, but untrained young men who are subjected to a standardized six-week training program that involved elbow flexion contractions at 30% MVC in three groups à N=6 subjects:

• a high mental effort (HME, n = 6) group, in which the subjects performed biceps contractions at ~ 30% MVC while imagining (internal imagery) at the same time that they are contracting their muscle as hard as possible; 
• a low mental effort (LME, n = 6), group, in which the subjects performed biceps contractions at ~ 30% MVC while watching an entertaining video (e.g., a movie) of their choice; and 
• a no-training control (CTRL, n = 6) group, in which subjects participated in all measurement sessions, but did not undergo any training. 

It was hypothesized that the participants trained by the high effort elbow flexion task would gain a significant amount of strength but those trained by the low effort contractions would not despite the fact that both groups physically exercised at the same intensity level (30% MVC) and performed an otherwise identical MVC contraction protocol (30 reps lasting 30 s each followed by a 30-s rest) five days a week over the 6 week period (with 6 wks x 5 workouts/week = 30 workouts).

Figure 1: Measured training intensity (in % of MVC, left) and percent elbow flexion strength changes (right) in the high mental effort (HME), low mental effort (LME) and no-training control (CTRL) groups following a 6-week training program. Only the HME group had a significant strength gain (20.47%) after training (P < 0.05 | Jiang 2017).

And guess what: Even though there was no significant difference in the pre-training strength values between groups (F(2,15) = 0.166, P = 0.849), and notwithstanding ...

• the fact that the training intensity (elbow flexion force sustained during training) randomly sampled during the 6 week period was slightly higher (but not statistically significant, F(1,10) = 1.536, P = 0.244) for the LME than the HME group, ... 
• the lack of differences between periodically measured (~ twice a week) surface EMG in the biceps brachii (BB) and brachioradialis (BR) muscle during training between the HME and LME groups, ...

the scientists' within-group comparisons revealed that the strength increased significantly after training in the HME group (t(5) = 2.405, P = 0.03), but the change was not significant in the LME group (t(5) = − 1.086, P = 0.16). Group comparisons in percent (%) strength change (post-training vs. pre-training) indicated that the increase was significantly greater in HME (20.47 ± 8.33%) than LME (1.89 ± 0.96%) and CTRL (− 3.27 ± 2.61%) groups (F(2,15) = 6.065, P = 0.01). Figure 1, right, shows strength changes (relative to each group's baseline) in the three groups.
References:

• Grosprêtre, Sidney, Célia Ruffino, and Florent Lebon. "Motor imagery and cortico-spinal excitability: a review." European journal of sport science 16.3 (2016): 317-324.
• Jiang, Chang-Hao, et al. "The level of effort, rather than muscle exercise intensity determines strength gain following a six-week training." Life Sciences (2017).
• Ranganathan, Vinoth K., et al. "From mental power to muscle power—gaining strength by using the mind." Neuropsychologia 42.7 (2004): 944-956.
• Roland, Per E., et al. "Supplementary motor area and other cortical areas in organization of voluntary movements in man." Journal of neurophysiology 43.1 (1980): 118-136.
• Vingerhoets, Guy, et al. "Motor imagery in mental rotation: an fMRI study." Neuroimage 17.3 (2002): 1623-1633.
• Yue, Guang, and Kelly J. Cole. "Strength increases from the motor program: comparison of training with maximal voluntary and imagined muscle contractions." Journal of neurophysiology 67.5 (1992): 1114-1123.