Do interventions involving repetitive practice improve strength after stroke? Are any improvements in strength accompanied by improvements in activity?
Imagine that the New Year has just begun. You’ve made a resolution to improve your physical fitness. In particular, you want to improve your muscle strength. You’ve heard that people with stronger muscles live longer and have less difficulty standing, walking, and using the toilet when they get older (Rantanen et al. 1999; Ruiz et al. 2008). So, you join a fitness centre and hire a personal trainer. The trainer assesses your maximal strength, and then guides you through a 4-week program that involves lifting weights which are about 80% of your maximum.
Sure enough, after the program, you become stronger (probably around 20% stronger) (Carroll et al. 2011). You think this is great – and it is! You are so excited, you decide to stand in front of your mirror, flex your biceps, and take a selfie (your plan is to post the picture to Facebook to show your friends how much bigger your muscles got). However, after examining the picture, you realise your muscles did not get bigger. Or perhaps they did get a little bigger, but not enough to explain your substantial improvement in strength. You are somewhat disappointed in this, but then you remember your goal was to get stronger, not necessarily bigger, so you post the picture, anyway.
Interestingly, the observations you made are completely consistent with the scientific literature. Within the first weeks of strength training, muscle strength can improve without a change in the size or architecture of the muscle (e.g., Blazevich et al. 2007). Consequently, researchers have speculated that initial improvements in muscle strength from strength training are due primarily to changes in the central nervous system. One hypothesis has been that strength training helps the nervous system learn how to better “drive” or communicate with muscles. This ability is termed voluntary activation, and it can be tested by stimulating the motor area of an individual’s brain while they perform a maximal contraction (Todd et al. 2003). If the stimulation produces extra muscle force, it means that the individual’s nervous system was not maximally activating their muscles. Currently, there is no consensus as to whether voluntary activation can actually be improved by strength training.
Therefore, we conducted a randomised, controlled trial in which one group of participants completed four weeks of strength training, while a control group did not complete the training (Nuzzo et al. in press). For the group who performed the training, each exercise session consisted of four sets of strong contractions of the elbow flexor muscles (i.e., the muscles that bend the elbow, such as the biceps). Before and after the four week intervention, both groups were tested for muscle strength, voluntary activation, and several other measures. The participants were healthy, university-aged, and they had limited or no experience with strength training.
Prior to the intervention, the strength training and control groups had similar levels of muscle strength and activation of the elbow flexor muscles. After the intervention, the group who performed the strength training improved their strength by 13%. They also improved their voluntary activation from 88.7% to 93.4%. The control group did not improve muscle strength or voluntary activation.
The results from our study show that four weeks of strength training improves the brain’s ability to “drive” the elbow flexor muscles to produce their maximal force. This helps to explain how muscles can become stronger, without a change in muscle size or architecture. Moreover, the results suggest that clinicians should consider strength training as a treatment for patients with motor impairments (e.g., stroke), as these individuals are likely to have poor voluntary activation (Bowden et al. 2014).
Nuzzo JL, Barry BK, Jones MD, Gandevia SC, Taylor JL. Effects of four weeks of strength training on the corticomotoneuronal pathway. Med Sci Sports Exerc, doi: 10.1249/MSS.0000000000001367.
Blazevich AJ, Gill ND, Deans N, Zhou S. Lack of human muscle architectural adaptation after short-term strength training. Muscle Nerve 35: 78-86.
Bowden JL, Taylor JL, McNulty PA. Voluntary activation is reduced in both the more- and less-affected upper limbs after unilateral stroke.Front Neurol 5: 239, 2014.
Carroll TJ, Selvanayagam VS, Riek S, Semmler RG. Neural adaptations to strength training: moving beyond transcranial magnetic stimulation and reflex studies. Acta Physiol 202: 119-140, 2011.
Rantanen T, Guralnik JM, Foley D, Masaki K, Leveille S, Curb JD, White L. Midline hand grip strength as a predictor of old age disability.JAMA 281: 558-560, 1999.
Ruiz JR, Sui X, Lobelo F, Morrow Jr. JR, Jackson AW, Sjöström M, Blair SN. Association between muscular strength and mortality in men: prospective cohort study. BMJ 337: a439, 2008.
Todd G, Taylor JL, Gandevia SC. Measurement of voluntary activation of fresh and fatigued human muscles using transcranial magnetic stimulation. J Physiol 555: 661-671, 2003.
Jim Nuzzo is a Postdoctoral Fellow at Neuroscience Research Australia (NeuRA). His research investigates how strength training alters the neural connections between the brain and muscles. Click here to read Jim’s other blogs.
To evaluate a wearable sensor-based toolkit for quantifying muscle tone in patients with upper motor neuron syndrome (UMNS).
|Effects of ankle biofeedback training on strength, balance, and gait in patients with stroke|
|Kim S-J, Cho H-Y, Kim K-H, Lee S-M|
|Journal of Physical Therapy Science 2016 Sep;28(9):2596-2600|
|PURPOSE: This study aimed to investigate the effects of ankle biofeedback training on muscle strength of the ankle joint, balance, and gait in stroke patients. SUBJECTS AND METHODS: Twenty-seven subjects who had had a stroke were randomly allocated to either the ankle biofeedback training group (n = 14) or control group (n = 13). Conventional therapy, which adhered to the neurodevelopmental treatment approach, was administered to both groups for 30 minutes. Furthermore, ankle strengthening exercises were performed by the control group and ankle biofeedback training by the experimental group, each for 30 minutes, 5 days a week for 8 weeks. To test muscle strength, balance, and gait, the Biodex isokinetic dynamometer, functional reach test, and 10 m walk test, respectively, were used. RESULTS: After the intervention, both groups showed a significant increase in muscle strength on the affected side and improved balance and gait. Significantly greater improvements were observed in the balance and gait of the ankle biofeedback training group compared with the control group, but not in the strength of the dorsiflexor and plantar flexor muscles of the affected side. CONCLUSION: This study showed that ankle biofeedback training significantly improves muscle strength of the ankle joint, balance, and gait in patients with stroke.
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A recent advancement in the study of physical rehabilitation is the application of virtual reality rehabilitation (VRR) programs, in which patients perform practice behaviors while interacting with the computer-simulation of an environment that imitates a physical presence in real or imagined worlds. Despite enthusiasm, much remains unknown about VRR programs. Particularly, two important research questions have been left unanswered: Are VRR programs effective? And, if so, why are VRR programs effective? A meta-analysis is performed in the current article to determine the efficacy of VRR programs, in general, as well as their ability to develop four specific rehabilitation outcomes: motor control, balance, gait, and strength. A systematic literature review is also performed to determine the mechanisms that may cause VRR program success or failure. The results demonstrate that VRR programs are more effective than traditional rehabilitation programs for physical outcome development. Further, three mechanisms have been proposed to cause these improved outcomes: excitement, physical fidelity, and cognitive fidelity; however, empirical research has yet to show that these mechanisms actually prompt better rehabilitation outcomes. The implications of these results and possible avenues for future research and practice are discussed.
Mobility and the Lower Extremity
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Muscle weakness is a common consequence of stroke and can result in a decrease in physical activity. Changes in gait performance can be observed, especially a reduction in gait speed, and increased gait asymmetry, and energy cost is also reported.
The aim was to determine whether strengthening of the lower limbs can improve strength, balance and walking abilities in patients with chronic stroke.
Five databases (Pubmed, Cinhal, Cochrane, Web of Science, Embase) were searched to identify eligible studies. Randomized controlled trials were included and the risk of bias was evaluated for each study. Pooled standardized mean differences were calculated using a random effects model. The PRISMA statement was followed to increase clarity of reporting.
Ten studies, including 355 patients, reporting on the subject of progressive resistance training, specific task training, functional electrical stimulation and aerobic cycling at high-intensity were analysed. These interventions showed a statistically significant effect on strength and the Timed Up-and-Go test, and a non-significant effect on walking and the Berg Balance Scale.
Progressive resistance training seemed to be the most effective treatment to improve strength. When it is appropriately targeted, it significantly improves strength.
[Purpose] This research demonstrated a forced intensive strength technique as a novel treatment for muscle power and function in the affected upper extremity muscle to determine the clinical feasibility with respect to upper extremity performance in a stroke hemiparesis.
[Subject and Methods] The subject was a patient with chronic stroke who was dependent on others for performing the functional activities of his affected upper extremity. The technique incorporates a comprehensive approach of forced, intensive, and strength-inducing activities to enhance morphological changes associated with motor learning of the upper extremity. The forced intensive strength technique consisted of a 6-week course of sessions lasting 60 minutes per day, five times a week.
[Results] After the 6-week intervention, the difference between relaxation and contraction of the affected extensor carpi radialis muscle increased from 0.28 to 0.63 cm2, and that of the affected triceps brachii muscle increased from 0.30 to 0.90 cm2. The results of clinical tests including the modified Ashworth scale (MAS; from 1+ to 1), muscle strength (from 15 to 32 kg), the manual function test (MFT; scores of 16/32 to 27/32 score), the Fugl-Meyer assessment (FMA; scores of 29/66 to 49/66 score), and the Jebsen-Taylor hand function test (JTHFT; from 38/60 to 19/60 sec) were improved.
[Conclusion] Our results suggest that the forced intensive strength technique may have a beneficial effect on the muscle size of the upper extremity and motor function in patients with chronic stroke.