Neuromuscular and Functional Adaptations Promoted by Lower Limb Isometric Training with NMES Conditioning Contractions in Older Adults

Highlights: Public health relevance—How does this work relate to a public health issue? The present work addresses the effects of two training modalities on strength, power and functional capacities in older adults. The aforementioned factors are strongly related to the health and functional independence of this population, which is one most in need of public health interventions. Public health significance—Why is this work of significance to public health? This work broadens the knowledge related to the implementation of isometric training and neuromuscular electrical stimulation for improving health-related factors in older adults. In this population, physical activity is particularly beneficial to delay and sometimes offset the age-related loss of strength, power and overall functional independence, thus improving quality of life. Public health implications—What are the key implications or messages for practitioners, policy makers and/or researchers in public health? The present study shows that a combination of isometric training and neuromuscular electrical stimulation implemented unilaterally improves strength, power and functional capacities in older adults. The proposed training intervention also promoted a small but significant cross-education effect. Hence, the proposed approach may also be considered in situations where only one limb can be exercised (i.e., rehabilitation settings). Aging induces sarcopenia and reduces bone mineral density, altering body composition. These modifications contribute to physical decline, increase non-communicable disease risk and increase the likelihood of hospitalization, thereby representing a substantial public health burden. In this study, we assessed the effects of isometric training with neuromuscular electrical stimulation conditioning contractions (ISO-NMES) and dynamic resistance training (DRT) on physical and functional capacities. Moreover, we investigated the impact of ISO-NMES training on the force and power of the trained and untrained leg. Eighteen sessions of ISO-NMES training for knee extensors were performed by 10 older adults (age: 70.1 ± 4.9 years; ISO-NMES group). The DRT group (n = 12; age: 70.5 ± 2.8 years) performed 18 sessions of dynamic resistance training at a local fitness center. Maximum voluntary contraction (MVC) and peak power (P) of lower limbs as well as functional capacities assessed with the 5 Sit to Stand, Timed Up and Go and 6 Minutes Walking Tests were examined in both groups before and after the related training protocols. At the end of the training period, only the ISO-NMES group had improved MVC (+30.4%, p < 0.001) and bilateral force (ISO-NMES: +6.3%, p = 0.032). Moreover, both groups had significantly improved functional capacities. Finally, in the ISO-NMES group, MVC, force and power significantly increased in both legs with a greater effect for MVC in the trained than untrained leg (+30.4 vs. +13.5%, p < 0.001). These findings suggest that ISO-NMES training was an effective strategy to improve physical and functional capacities in older adults. Thus, it could be considered as a potential intervention, particularly when the mobility to perform physical training is limited.