Physical activity and MND – part 2
This is part two of our series of blogs looking at links between physical activity and MND. This article will look at whether or not exercise should be continued after diagnosis.
Exercise is widely recommended to the general population due to its benefits to health and wellbeing. It improves the cardiovascular, respiratory, musculoskeletal, and endocrine functions and leads to psychological wellbeing. Many people with MND specifically ask whether they can safely continue to exercise regularly without fear of accelerating their disease. At present, there is no firm evidence that exercise exerts a harmful effect, although avoidance of very strenuous activity would seem to be sensible. Low-grade, managed, exercise programmes may even be of benefit.
For many people with MND, exercise played an integral role in their pre-diagnosis lives. A wish to continue exercising, in the hope it will have positive effects on endurance and strength, is understandable. While pre-diagnosis exercise is likely to have involved aerobic training and strengthening programmes, research has shown that moderate endurance exercise can slow functional decline whereas high intensity training can be detrimental.
One of our care team colleagues, who worked as a physiotherapist, says that early in the disease exercise is encouraged to keep good movement in the muscles and to keep function for as long as possible. Once the motor neurones that control a particular muscle have weakened, the muscle cannot be repaired by exercise or anything else but exercise can help to keep weakened muscles as strong as possible. It will also help to strengthen muscles that have not yet been affected. Regular exercise can help maintain muscle elasticity, improve range of movement for joints and prevent muscles from shortening. You may find our information sheet on physiotherapy of interest.
How might ‘science’ determine what kind of exercise is safe and effective?
At last year’s International Symposium on ALS/MND, organised by the MND Association, Dr Nicholas Maragakis, of Johns Hopkins Hospital, gave a presentation about a trial that looked at resistance and endurance exercise in MND. Resistance exercises increase muscle strength by making your muscles work against a weight or force. Endurance exercises are any activity that increases your heart rate and breathing for an extended period of time. Its objective was to evaluate the safety and tolerability of both kinds of exercise in MND participants, as measured by their ability to complete the six month study. Fifty nine participants were randomised to resistance, endurance or stretching/range of movement (SROM – the exercise regimen prescribed for most MND patients). The study demonstrated that SROM, resistance and endurance exercises are all safe to be performed, to a clinician-specified routine. Other benefits included decreased risk of falls due to mobility problems associated with MND. You can listen to a webinar of Dr Maragakis’ study here.
Swimming to alleviate some of the symptoms of MND
In another 2017 study, researchers in France studied the effects of high intensity swimming exercise. They found that SOD1 mice suffered from severe glucose intolerance and that this was counteracted by a high intensity swimming exercise. This exercise also restored the highly MND-sensitive tibialis muscle (the muscle located near the shin) through the production of key glucose transporters. Glucose is the primary source of energy for most cells but its molecules cannot get through the lipid membrane (the outside ‘shell’) of the cell on their own – they need the help of glucose transporters including GLUT4 and GADPH. Defects in the production of these vital transporters are observed in the muscles of MND patients. These observations suggest that the use of specific physical exercise may alleviate some of the symptoms of MND.
Developing individual exercise programmes
As part of the standard care for MND, general exercise recommendations are made with instructions for stretching, range of motion exercises and balance and are based on preclinical data, small human studies and research on exercise in other neuromuscular diseases. Recent and increasing evidence in animal models and human studies reinforces the benefits of an exercise programme, suggesting that moderated endurance exercise can delay disease progression and increase survival.
Aerobic exercise is generally performed at a moderate level of intensity. ‘Aerobic’ means the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism, which is linked to the cardiorespiratory and vascular system’s capacity to supply oxygen to the muscles, and the ability to clear carbon dioxide from the blood via the lungs.
When the intensity of the exercise exceeds the rate of oxygen supply to the muscles, lactic acid builds up – this is one of the causes of muscle cramps – which makes it difficult and painful to continue exercising. The starting point of the increase of lactic acid during a cardiopulmonary exercise testing (CPET) is called the anaerobic threshold (AT). In people with MND, the AT may occur sooner than expected due to respiratory muscle weakness. In order for a clinician to prescribe a moderate exercise programme, that will not take the patient over their AT, CPET can be used with gas exchange analysis once the AT has been established.
As the processes by which nerve cells die are complex and multifactorial (meaning there is more than one cause), it is relevant to evaluate the effects of a moderate aerobic exercise with controlled intensity determined by CPET and its role on the functional status of people with MND compared to those who receive standard care.
A study by Braga and colleagues, published in early 2018, aimed to establish the point at which moderate exercise became painful for people with MND so that a personal exercise regime may be implemented, 48 patients were split into two groups – G1 and G2. All participants formed a standard care exercise programme which included daily exercises such as range of motion exercise, and balance and gait training. In addition, patients in G1 performed an aerobic exercise twice a week on a treadmill with intensity determined by CPET. At the beginning of the trial, the ALSFRS scores were not significantly different between groups. At the end of the study (6 months) the ALSFRS score for G1 was significantly higher, reflecting slower functional decline.
This is the first exercise trial applying a moderate exercise protocol with intensity rates precisely defined and would seem to suggest that a strictly monitored moderate exercise programme may significantly reduce motor deterioration in people with MND, although not improve survival.
Exercising in your own home
Another study from early 2018, by Kitano and colleagues, was to confirm the effects of structured home-based exercises without supervision by a physical therapist on people who were newly diagnosed with MND.
Twenty one patients were enrolled and designated as the Home-EX group. They performed unsupervised home-based exercises, which included muscle stretching, muscle training and functional training for six months. A control group of 84 people with MND underwent supervised exercise with a physical therapist for six months.
In the Home-EX group, 15 participants completed the home-based exercises for six months. This group was found to have a significantly higher respiratory function score and total score on ALSFRS than the control group after six months. This would suggest that structured home-based exercises without supervision by a physical therapist could be used to alleviate functional deterioration in people newly diagnosed with MND.
More about the neuroprotective benefits of exercise
A 2009 study by Deforges and colleagues compared the neuroprotective qualities of swimming versus running exercise in an MND SOD1 mouse model. Neuroprotection refers to the preservation of the structure and/or function of a neurone. They also compared the two exercises to sedentary MND mice and healthy controls.
The researchers found that, at 115 days of age, there were remarkable differences in the neuroprotective potentials of each exercise. A dramatic neuron loss was seen in the sedentary and the running MND mice with a 49% and 45% reduction respectively. In contrast, the mice who undertook the swimming exercise exhibited only a 28% reduction of motor neurons, giving rise to the possibility that this type of exercise may be neuroprotective. The researchers also observed that the swimming exercise maintained certain muscles in the leg in a way close to the corresponding muscles in the healthy controls. The swimming exercise also led to a 20% increase in life span compared to the SOD1 mice in the running and sedentary groups.
The BIG question – should I continue exercising after diagnosis?
The evidence would suggest – YES! Even if you didn’t exercise very much before diagnosis these studies, and others like these, strongly support the idea that moderate prescribed exercise is recommended after diagnosis. The other thing taken from the studies is that advice should always be sought from a trained clinician before embarking on any exercise regime post-diagnosis. The clinician will help find the activity that best suits the individual and tailor this to meet their specific needs. They will also monitor and help to modify exercise plans as needed. You may find ‘7 tips for starting an exercise programme’, published in ALS News Today in November 2017, interesting and helpful.
Part three in this series takes a look at some of the other factors associated with physical activity that may influence the development of MND, such as a genetic predisposition to athleticism and oxidative stress.