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Neuromuscular electrical stimulation
Published in Claudio F. Donner, Nicolino Ambrosino, Roger S. Goldstein, Pulmonary Rehabilitation, 2020
Matthew Maddocks, Isabelle Vivodtzev
In addition to its peripheral effect, it is important to know that NMES has an action on the central nervous system by soliciting the entire chain of command and force production. Indeed, NMES induces a bidirectional propagation of the action potential generated leading to a reflex stimulation of the sensory fibres (both muscle and cutaneous afferent fibres), which, in turn, enhances the excitability of the corticomotor pathway (34–37). Hence, acute NMES application does not bypass the central nervous system. On the contrary, unilateral NMES training programme may increase electromyographic activity, neural activation (38) and voluntary force of the contralateral (unstimulated) muscle (39), inducing a cross-education effect. This central effect of NMES may explain why improvements in muscle strength are often irrespectively higher than improvement in muscle mass in patients with COPD (see ‘Clinical effects of NMES’ in this chapter). In addition, it would confirm the likelihood that 12 training sessions are necessary but sufficient to induce an increase in muscle strength in healthy subjects (40). Hence, NMES may not only improve muscle mass but also act on muscle central activation, an important part of muscle strength known to be dampened in patients with severe COPD (41).
Stretching effects on injury reduction and health
Published in David G. Behm, The Science and Physiology of Flexibility and Stretching, 2018
Another factor contributing to a more inflexible muscle with immobilization would be a relative increase in connective tissue, because connective tissue degrades at a slower rate than muscle tissue, contributing to a stiffer muscle (53,54). In addition, there is reported to be a more acute angle of collagen to the axis of the muscle fibres compared with healthy muscle (55) which would also affect stiffness. Third, immobilization reduces the water and glycosaminoglycan content of connective tissue, decreasing the distance between collagen fibres and resulting in abnormal cross-linkages that limit extensibility of the tissue (56,57). Stretching tends to counter these deleterious effects (58). However, an immobilized limb in a cast may be difficult to stretch in order to prevent or reduce the decreased extensibility. A counter-measure that may be incorporated while the muscle is still immobilized is to stretch the contralateral muscle or actually any other muscle. Unilateral stretching of the hamstrings has improved the ROM of the contralateral hip flexors (59). Furthermore, stretching either the shoulders or the adductor (groin) muscles resulted in improved ROM in the hip flexors and shoulders, respectively (60). So, stretch your upper body and your lower body becomes more flexible or stretch your lower body and your upper body becomes more flexible. This is important information for individuals who are immobilized. Just like cross-education (strength increase in contralateral muscle after unilateral training) (61–64) is important to preserve strength in an immobilized muscle, stretching unaffected muscles should help to preserve flexibility or at least help to minimize loss of flexibility during immobilization.
Effects of Cross-Education on Neural Adaptations Following Non-Paretic Limb Training in Stroke: A Scoping Review with Implications for Neurorehabilitation
Published in Journal of Motor Behavior, 2023
Hyosok Lim, Sangeetha Madhavan
A growing body of evidence has demonstrated the potential importance of contralesional pathways toward functional recovery, providing a potential solution for harnessing plasticity within the contralesional hemisphere to facilitate functional recovery in severe stroke (Bradnam et al., 2013; Buetefisch, 2015). Unilateral motor training, which has been extensively studied in healthy individuals and some patient populations, has demonstrated bilateral training effects (Green & Gabriel, 2018). This phenomenon, termed as ‘cross-education’, is defined as the transfer of strength or motor skill gains to the contralateral untrained limb following unilateral motor training (Ruddy & Carson, 2013). The bilateral changes in corticomotor activation that accompanies cross-education are termed as ‘cross-activation’ (Ruddy & Carson, 2013). The mechanisms of cross-education and cross-activation provide unique opportunities for enhancing functional capacity of a weaker or incapacitated limb and have high clinical relevance as an intervention for individuals with stroke, especially those with severe hemiparesis who have limited movements on the paretic side. In addition, cross-activation can also be a potential motor priming mechanism, where improvements in neural activity in the lesioned hemisphere can be elicited by movements of the non-paretic limb to facilitate long-term potentiation and optimize motor training (Stoykov et al., 2017).
Clinician perspectives on cross-education in stroke rehabilitation
Published in Disability and Rehabilitation, 2018
William Russell, Lesley Pritchard-Wiart, Patricia J. Manns
Cross-education could potentially be a treatment option for those with more impaired arm function. Cross-education is training on one side of the body that results in a positive effect on the opposite untrained side [7]. In people with stroke, cross-education would consist of training the less affected side, with the expectation of benefit on the weaker side. Cross-education was first described in 1894 [8] and has been studied throughout the last 120 years. In a systematic review and meta-analysis with a healthy adult population, the cross-education effect was found to be a 7.6% increase of strength on the untrained limb or approximately half of the strength increase on the trained limb. The effect of cross-education was found to be real but small [7].
The effect of unilateral training on contralateral limb strength in young, older, and patient populations: a meta-analysis of cross education
Published in Physical Therapy Reviews, 2018
Lara A. Green, David A. Gabriel
Cross education is the strength gain that is found in the contralateral limb following a unilateral training program on the homologous limb. Cross education was first reported in 1894 by Scripture et al. [1] who determined that task steadiness and muscular strength could be improved in the contralateral limb following unilateral training. This phenomenon is of great importance for clinical applications and rehabilitation, and requires further mechanistic investigation. Cross education provides a beneficial rehabilitation model for unilateral injuries or disorders; including, acute injuries or immobilization (casting) of a single limb, and neurologic disorders, such as stroke, affecting the body unilaterally.