Trainability of leg strength by whole-body electromyostimulation during adult lifespan: a study with male cohorts

BACKGROUND: The age-related decline in muscle strength is a well documented phenomenon in human beings. Resistance-type exercise including the novel, joint-friendly, and time-efficient whole-body electromyostimulation (WB-EMS) technology decelerates this unfavorable decline. However, the issue of trainability of the neuromuscular system during different periods of life still remains, especially for WB-EMS. Thus, the aim of this study was to compare the changes in maximum isokinetic leg/hip extensor strength (MIES) and maximum isokinetic leg/hip flexor strength (MIFS) after WB-EMS interventions in men in different periods of life. Our hypothesis was that although WB-EMS significantly increases lower extremity strength in all periods of adults’ life, trainability decreases with age with a significantly higher increase at the age of 20–35 years compared with that at the age of 65+ years. SUBJECTS AND METHODS: Using an isokinetic leg press, we determined the changes in MIES and MIFS in 118 community-dwelling men aged 27–89 years after 14–16 weeks of WB-EMS interventions applying identical protocols. Men were structured in 15 year-ranged age groups starting at the age of 20–35 years and ending at the age of 80+ years. RESULTS: Most importantly, WB-EMS-induced gains in MIES and MIFS were significant (P<0.001) in all the groups. Changes in MIFS were on average about twice as high compared with MIES (18–25% vs 9–15%). Applying one-way ANOVA, we observed a trend to lower trainability with increasing age (P=0.060) for MIES. Pairwise tests confirmed our hypothesis that the youngest subgroup differs significantly for MIES from men aged 65+ years (P=0.007). In parallel, one-way ANOVA determined a significant between-group difference (P=0.046) for MIFS; however, we did not determine a significant difference between men aged <35 years and 65+ years. CONCLUSION: We observed an inconsistent tendency for blunted WB-EMS-induced lower extremity strength gains in older adults. However, much more importantly, the general effectiveness of WB-EMS to significantly increase maximum hip/leg strength during the adult lifespan can be confirmed.