Strength Training in Spinal Cord Injury
- 1 Introduction
- 2 Definition
- 3 Assessment of Strength
- 4 Response to Strength Training
- 5 Exercise Prescription
- 6 Resources
- 7 References
Poor strength is the first impairment considered by most physiotherapists in relation to spinal cord injury, and can be both neurally induced or occur in neurally intact muscles. with motor tasks often limited by the strength of completely paralysed, partially paralysed or non-paralysed muscles.
- Loss of strength in neurally intact muscles, particulary during the acute phase of spinal cord injury can have a significant impact on function, and tends to occur as a result of disuse atrophy or insufficient strength for the demands of novel functional tasks ie. transfers, wheelchair mobility etc.
- Paralysis (complete disruption to descending motor pathways) or partial paralysis (particla disruption to descending mootor pathways) result in neurally induced weakness or loss of strength.
Strength training, also referred to as resistance training can be thought of as voluntary activation of the muscles against resistance, and refers to any form of exercise where you lift or pull against resistance, which can can take the form of body weight, free weights, machine resistance, powerbands, or any other external form of resistance. Strength training can elicit numerous positive benefits on your health and well being, not only increasing strength but increased bone, muscle, tendon, and ligament strength and toughness which can reduce the occurrence of sarcopenia, which is the age-related decline in muscle, and decrease the risk of osteoporosis, improved joint function, increased bone density, increased metabolism, increased fitness , improved cardiac function, and has been linked to decreased pain, stress and depression, often resulting in reduced potential for injury. Regular strength training has also been linked to decreased risk of cardiovascular disease through decreased body fat, decreased blood pressure, improve cholesterol profile, and lower the stress placed on the heart while lifting a particular load. In individuals with a spinal cord injury these benefits can have a positive impact on quality of life and often result in making activities of daily living more efficient e.g. transfers etc.
Strength training programmes progressively increasing the force output of the muscle through incremental increases in resistance / weight and should always use uses a range of exercises (push, pull, upper body, lower body, trunk etc.) and types of equipment to target specific muscles or groups of muscles. Strength training is primarily an anaerobic activity, although some proponents have adapted it to provide the benefits of aerobic exercise through circuit training or high intensity interval training.
Physiotherapy treatment is directed at neurally intact muscles and in those areas with only partial paralysis, as the muscle with paralysis has complete disruption of the descending motor pathways and can not be improved with strength training. voluntary strength of paralysed muscle can not be improved with strength training.
According to the Oxford Dictionary of Sport Science and Medicine, strength training are any exercises performed specifically to develop strength, which involves weight training using progressive resistance exercises incorporating a repetition maximum that ensures overload of the muscle. 
Assessment of Strength
An assessment of muscle strength is typically performed as part of a patient's objective assessment to assist the physiotherapist's clinical reasoning and enable them to reason an appropriate point to begin strengthening rehabilitation from. Muscle strength can be assessed by a number of methods: manually, functionally or mechanically including the following; 
Manual Muscle Test
Manual Muscle Testing (MMT) is a standardized set of assessments that measure muscle strength and functionagainst specific criteria and is commonly used in clinical practice by physiotherapists to measure strength in individuals with a spinal cord injury. During manual muscle testing, each muscle group is tested bilaterally. There are a number manual muscle testing systems available, the most well known of which are the Medical Research Council Scale (also known as the Oxford Scale), Daniels and Worthingham and Kendall and McCreary.
Despite some of the inherent problems of manual muscle tests, they are still useful for broadly identifying neurological weakness and detecting marked neurological deterioration or improvement. This is particularly important for individuals with an acute spinal cord injury when it is important to monitor the effects of interventions such as surgical decompressions, although it can be less sensitive at detecting changes in strength with grades 3+, 4 and 4+/5, where hand held myometry more sensitive. Manual muscle tests are also useful because the results are readily interpretable by all, including patients. Manual muslce testing has adequate to excellent psychometric properties in patients with spinal cord injury, including excellent interrater reliability (ICC = 0.94) and convergent validity and is easily integrated into clinical practice. 
The following links demonstrate Manual Muscle Testing of specific joints and movements:
One Repitition Maximum
One Repetition Maximum (1 RM), refers to the maximum weight a patient can lift through an entire range of motion against gravity, and can be used to determine muscle strength for muscle groups with Grade ⅘ or greater strength. Testing for 1RM involves adjusting the weight until it can be lifted but not more than once, ensuring sufficient rest between each attempt to avoid fatigue. In muscles with Grade ⅗ strength, a ‘Modified’ 1 RM can be used by moving the weight horizontally, instead of lifting a weight against gravity, often with the limbsupported using slideboards or overhead suspension
Hand Held Myometer
Myometers, predominantly small, portable handheld devices, either mechanical or electronic, can be used to test for isometric strength providing a measures of force, rather than torque. While it provides an objective, quantifiable method of measuring muscle strength, this does not necessarily reflect function. It may superior to manual muscle testing for detection of mild to moderate weakness and changes in muscle strength, particulalry in the upper limb. It also eliminates potential bias from the evaluator for various age groups and gender.Examiner may have difficulty stabilizing muscle or joint for strong individuals. While it can be difficult to utilise with a stronger individual, particularaly when testing the larger lower limb muscles, they can be useful for testing strength in individuals on bed rest and is primarily utilised in strength testing for upper limb in spinal cord injury. There are some limitations for use with individuals with a spinal crod injury due to inability to use with muscle grades <3/5.
Hand held myometry has Low to High Inter-rater reliability (ICC=0.21-0.89), variability may be due to the lack of standardization for starting position and for muscles tested, while Intra-rater reliability is High (ICC=0.93-0.99). Validity was Low to High for individuals with paraplegia (Spearman’s r=0.26-0.67) and Moderate to High for individuals with tetraplegia (Spearman’s r=0.50-0.95). 
Isokinetic Dynamometer is less commonly used in cilnical practice but has the advantage of using a ratio scale for measurement, measuring torque during dynamic (concentric or eccentric) contractions at a constant angular velocity. Equipment is both expensive to buy initially, is more complex to adjust when testing multiple muscle groups, and not appropriate for those with profound weakness or those restricted to bedrest.
Response to Strength Training
The basic principles of strength training involve a manipulation of the number of repetitions, sets, tempo, exercises and force to cause desired changes in strength, endurance or size by overloading of a group of muscles. The specific combinations of reps, sets, exercises, resistance and force depend on the purpose of the individual performing the exercise: to gain size and strength multiple (4+) sets with fewer reps must be performed using more force. A wide spectrum of regimens can be adopted to achieve different results, but the classic formula recommended by the American College of Sports Medicine reads as follows:
To stimulate increased strength, the muscle must work harder than it has previously worked, workloads should be at a higher level than normally encountered. As the muscle adapts to a particular workload, the individual should progress to a higher load, as such as the muscle becomes stronger the load has be be increased progressively over time to stimulate further strength increases. This should be monitored carefully to ensure the loads are not too high for the muscle to cope with, thus increasing the risk for overtraining and overuse injuries, particularly in an individual with a spinal cord injury who rely on the upper limb for mobility, and have less opportunity to rest the upper limb following strength training.
FrequencyRefers to the number of training sessions per unit of time, typically over a week. The rate of recovery from a strength training session appears to be limited by the rate f recovery of the muscle cell, which typically takes longer than 24 hours and therefore training the same muscle two days in a row intensely with resistance is not recommend. Training a muscle before it has recovered can increase the risk of overtraining, while training too infrequent can result in under training and may fail to produce an optimal training response. In line with the new Spinal Cord Injury Exercise Guidelines to improve strength, adults with a spinal cord injury should engage in;
Strength Exercises for each major functioning muscle group 2 times per week
IntensityRefers to the amount of resistance or load being lifted. Recommendations use a percentage of one repetition maximum. Modifying the load, number of repetitions, speed of repitions, and rest between sets are ways of modifying the intensity of strength training. In line with the new Spinal Cord Injury Exercise Guidelines to improve strength, adults with a spinal cord injury should engage in;
Strength Exercises for each major functioning muscle group, at a Moderate-Vigorous Intensity
VolumeRefers to the total amount of work performed during a strength training session. It can be thought of as the product of Number of Reps x Number of Sets x Number of Exercises x Load. Volume of training over a week can be taught of as the number of training sessions x the amount of work done in those sessions. In line with the new Spinal Cord Injury Exercise Guidelines to improve strength, adults with a spinal cord injury should engage in at least;
3 Sets of Strength Exercises for each major functioning muscle group 2 times per week
Adaptations that take place as a result of training are directly related to the type of training undertaken and are specific to the way the training is performed. The more specific the exercise the better transference into performance improvement in the area you are trying to improve. So when strength training with an individual with a spinal cord injury around specific functional tasks e.g transfers, then it is best done as far as possible within the context of that specific motor task.
Low repetition training ( < 5 Reps ) with high loads causes large increase in strength but minimal increase in muscle size.
Moderate repetition training ( 6 - 15 Reps ) produces the greatest increase in muscle size but lower levels of maximal strength than low repetition training.
High repetition training ( 15 - 30 Reps ) results in less maximal strength than lower repetition training but produces greater muscular endurance.
Physical Activity Recall Assessment for People with Spinal Cord Injury (PARA-SCI) is a self-report physical activity measure for individuals with spinal cord injury. It aims to measure type, frequency, duration, and intensity of physical activity performed by individuials with a spinal cord injury who use a wheelchair as their primary mode of mobility.
The ProACTIVE SCI Toolkit, from SCI Action Canada, is designed to help physiotherapists work with individuals with a spinal cord injury to be physically active outside of the clinic. It's a step-by-step resource that uses three overarching strategies including education, referral, and prescription to develop tailored strategies that work for both the physiotherapist and the individual with a spinal crod injury.
Active Living Leaders is comprised of a series of peer-mentor training videos with a goal of helping people who would like to use the latest physical activity knowledge, sport resources, and transformational leadership principles to inform and motivate adults living with a spinal cord injury to lead more active lives.
SCI-U Physical Activity Course is a collection of modularized training sessions. It includes Modules on Living an Active Life, Ways to Get Fit, Overcoming Barriers and Reaching Your Goal.
SCI Action Canada's Knowledge Mobilization Training Series (KMTS) is a collection of modularized training sessions, with the goal of advancing physical activity knowledge and participation among individuals living with spinal cord injury. It includes Modules on the Physical Activity Guidelines and Physical Activity Planning.
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- Kahn JH, Tappan R, Newman CP, Palma P, Romney W, Tseng Stultz E, Tefertiller C, Weisbach CL. Outcome Measure Recommendations From the Spinal Cord Injury EDGE Task Force. Physical Therapy. 2016 Nov 1;96(11):1832-42.
- Chan CW, Miller WC, Querée M, Noonan VK, Wolfe DL, SCIRE Research Team. The Development of an Outcome Measures Toolkit for Spinal Cord Injury Rehabilitation: Création d’une Trousse de Mesures des Résultats pour la Réadaptation des Personnes ayant subi une lésion de la Moelle épinière. Canadian Journal of Occupational Therapy. 2017 Apr;84(2):119-29.