Reiser, M., Busch, D., & Munzert, J. (2007). Strength gains by imagination of muscle actions. ACSM Annual Meeting New Orleans, Presentation Number, 1820.

"It is well established that strength training of high intensity ( 90% of the one repetition maximum) leads to neural adaptations which contribute considerably to an improvement in maximal voluntary contraction force (MVC). As several studies report, such an enhancement of muscular activation can also be achieved following imagined muscle contractions (IMC training)."

This study attempted to clarify the extent strength training sessions could be replaced by imagined muscle contractions training. Whether imagined muscle contractions training effects differed in single-joint and multi-joint activities as well as in upper and lower limb tasks were investigated also. Healthy Ss underwent eight weeks of supervised strength training program. Following a four-week resistance training with submaximal loads, three groups with different combinations of real (maximal voluntary contractions) and mental (imagined muscle contractions) strength training (M75% (N = 24); M50% (N = 24); M25% (N = 20); M is the percentage of training that involved mental sessions) were compared to a maximum voluntary contractions only training group (M0%, N = 17) and a control condition without strength training (N = 84). Each of 12 training sessions consisted of either maximum voluntary contractions or imagined muscle contractions training. Maximum voluntary contractions training consisted of four sets of two maximal five-second isometric contractions with ten seconds of rest between sets. Imagined muscle contractions training followed a similar pattern. Ss practiced two of four exercises (leg press, bench press, calf raise, triceps extension). Test and training exercises were identical. Maximum voluntary contractions were measured before and after the intervention and again seven days after the program finish.

The imagined muscle contractions groups (M25%, M50%, and M75%) showed slightly smaller increases in maximum voluntary contractions (3.0% to 4.2%) than M0% (5.1%), but significantly stronger improvements than the control group. Compared to further strength gains in M0% after a week (9.4% altogether), imagined muscle contractions groups showed no “delayed” improvement, but the attained training effects remained stable. Imagined muscle contractions training of the upper limbs led to stronger maximum voluntary contractions improvements compared to the lower limbs (2.2% and 5.2%, respectively).

Implication. High-intensity strength training sessions can be replaced partly by imagined muscle contractions training sessions without considerable reduction of strength gains. Imagined muscle contractions training is an adequate supplementary method for improving muscle strength. Another value of this form of training is that it reduces the likelihood of injury that would be caused by the physical environment and action.

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