Strength Training in Spinal Cord Injury

Original Editor - Naomi O'Reilly

Top Contributors - Ewa Jaraczewska, Naomi O'Reilly, Kim Jackson, Admin, Jess Bell and Stacy Schiurring  

Introduction

Poor strength is the first impairment in spinal cord injury acknowledged by most physiotherapists and can be both neurally induced or occur in neurally intact muscles. Motor tasks often become limited by the strength of paralysed, partially paralysed or non-paralysed muscles. It can present itself as:

• Decrease strength in neurally intact muscles, especially in the acute phase of spinal cord injury. It has a significant impact on function and tends to occur as disuse atrophy or insufficient strength for the demands of novel functional tasks.
• Paralysis (complete disruption to descending motor pathways) or partial paralysis (particle disruption to descending motor pathways) result in neurally induced weakness or loss of strength.

Strength Training

Definition

According to the Oxford Dictionary of Sport Science and Medicine, strength training is any exercise performed specifically to develop strength, which involves weight training using progressive resistance exercises incorporating a repetition maximum that ensures overload of the muscle.

Benefits

Strength training also referred to as resistance training, can be thought of as voluntary activation of the muscles against resistance. It refers to any form of exercise where you lift or pull against resistance, which 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 one's health and well being. These benefits are strength improvement and increasing bone, muscle, tendon, and ligament strength and toughness. As a result, a reduction in the occurrence of sarcopenia can occur. Additional benefits include: decreased risk of osteoporosis and increased bone density, improved joint function, increased metabolism, increased fitness, and improved cardiac function. Strength training has been directly linked to decreased pain, stress and depression, often resulting in reduced potential for injury. Reduced risk of cardiovascular disease was also reported through body fat reduction, lowering blood pressure, improving cholesterol profile, and lowering stress placed on the heart while lifting a particular load. In the end, the quality of life of individuals with a spinal cord injury can improve.

Techniques

Strength training programmes progressively increase the force output of the muscle through incremental increases in resistance/weight. It should always use 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 and partially paralysed muscles because muscle with complete paralysis has disruption of the descending motor pathways, and its voluntary strength cannot improve.  

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.

Manual, functional or mechanical muscle strength assessment methods are available.

Manual Muscle Test

Manual Muscle Testing (MMT) is a standardised set of assessments that measure muscle strength and function against specific criteria and is commonly used in clinical practice by physiotherapists working with individuals with a spinal cord injury. During manual muscle testing, the examiner tests the left and right sides of the body. Several manual muscle testing systems are available. The most commonly used tests are the following:

• Medical Research Council Scale (also known as the Oxford Scale)
• Daniels and Worthingham
• Kendall and McCreary

Despite some of the inherent problems with manual muscle tests, they are still helpful for broadly identifying neurological weakness and detecting marked neurological deterioration or improvement. It is especially recommended for individuals with an acute spinal cord injury when the effects of interventions such as surgical decompressions should occur, although it can be less sensitive at detecting changes in strength with grades 3+, 4, and 4+/5, where handheld myometry is more sensitive. Manual muscle tests results are readily interpretable by all, including patients. It has excellent interrater reliability (ICC = 0.94) and convergent validity, and it can be easily integrated into clinical practice when treating individuals with spinal cord injury.

Read here about Manual Muscle Testing for specific joints and movements.

One Repetition Maximum

One Repetition Maximum (1 RM) refers to the maximum weight a patient can lift against gravity through an entire range of motion. It helps to determine muscle strength for muscle groups with grade ⅘ or greater. Testing for 1RM involves adjusting the weight until the patient can lift it 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 limb supported using slide boards 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 measure of force, rather than torque. While it provides an objective, quantifiable method of measuring muscle strength, this does not necessarily reflect function. It may be superior to manual muscle testing for detection of mild to moderate weakness and changes in muscle strength, particularly in the upper limb. It also eliminates potential bias from the evaluator for various age groups and gender. Examiners may have difficulty stabilising muscles or joints for strong individuals. While it can be difficult to utilise with a stronger individual, particularly 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 cord injury due to the inability to use with muscle grades lower than 3/5.

Handheld myometry has low to high inter-rater reliability (ICC=0.21-0.89). Variability may be due to the lack of standardisation for starting position and 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

An isokinetic dynamometer offers a ratio scale for measurement. In addition, it allows the calculation of the torque during dynamic (concentric or eccentric) contractions at a constant angular velocity. Equipment can be expensive to buy initially, is more complex to adjust when testing multiple muscle groups, and is not appropriate for those with profound weakness or those restricted to bedrest.

Response to Strength Training

Exercise Prescription

The basic principles of strength training involve repetitions, sets, tempo, type of exercises and force to cause desired changes in strength, endurance or size by overloading 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 muscle size and strength requires multiple (4+) sets with fewer reps and more power. Adaptation of various regimens allows to achieve different results, but the classic formula recommended by the American College of Sports Medicine includes overload, frequency, intensity, volume, and specificity.

Overload

When the goal is to increase the strength of the muscles,  the individuals' workloads should be at a higher level than they usually encounter. As the muscle adapts to a particular workload, the person should progress to a higher load. This process continues with each muscle adaptation to stimulate further strength increase.  Frequent monitoring should occur to ensure the demands placed are not too high for the muscle to cope with, thus increasing the risk for overtraining and overuse injuries.  An example can be 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.

Frequency

Frequency refers to the number of training sessions per unit of time, typically over a week. The estimated time of recovery from a strength training session appears to be limited by the rate of recovery of the muscle cell, which takes longer than 24 hours.  Therefore intensive training with resistance two days in a row for the same muscle is not recommended. Training muscles before they have recovered can increase the risk of overtraining, while training too infrequently can result in undertraining and may fail to produce an optimal 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

Intensity

Intensity refers to the amount of resistance or lifted load.  Borg rating of perceived exertion (RPE) is an outcome measure scale used in knowing exercise intensity prescription. It is used in monitoring progress and mode of exercise in patients undergoing rehabilitation and endurance training.

Borg RPE Scale		Borg CR10 Scale
Scoring	Level of Exertion	Scoring	Level of Exertion
6	No Exertion	0	No Exertion
7	Extremely Light	0.5	Very very Slight
8		1	Very Slight
9	Very Light	2	Slight
10		3	Moderate
11	Light	4	Somewhat Severe
12		5	Severe
13	Somewhat Hard	6
14		7	Very Severe
15	Hard (Heavy)	8
16		9	Very very Severe
17	Very Hard	10	Maximal
18
19	Extremely Hard
20	Maximal Exertion

In Borg RPE;

• 9 = ‘very light’ exercise which equals walking slowly for a few minutes at the own pace of a healthy individual.
• 13 = ‘somewhat hard’ but the individual is still able to continue the activity.
• 17 = ‘very hard’. A healthy person can continue but must push themselves beyond their comfort of being very fatigued.
• 19 = extremely strenuous exercise for most people, the hardest they have ever experienced.

Recommendations for intensity measurement can be modified using different resistance, the number and speed of repetitions, and rest between sets. 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

Volume

Volume refers to the total amount of work performed during a strength training session.

Single exercise volume has the following formula:

• The number of Reps x Number of Sets x Number of Exercises x Load.

The volume of training over a week is defined 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

Specificity

Adaptations as the result of training are directly related to the type and form of the training. They are specific to the way the training is structured. More specific exercise translates to better transference into performance improvement in the area you are trying to improve. For example, strength training with an individual with a spinal cord injury around transfers occurs within the context of this motor task.  

Low Repetition Training ( < 5 Reps ) with high loads causes a significant increase in strength but a minimal increase in muscle size.

Moderate Repetition Training ( 6 - 15 Reps ) produces a high increase in muscle size but a lower increase in maximal strength than the low number of reps.

High Repetition Training ( 15 - 30 Reps ) results in less maximal strength than lower repetition training but produces greater muscular endurance.

Adaptations for Strength Training

Equipment Adaptations

Various active hands aids can be used to assist individuals with a spinal cord injury to perform exercises in the gym using the equipment. Below are some examples of the exercises equipment and active hands aids:

• Free weights: active hands gripping aid, heavyweights gripping wrap, thumb protectors
• Weight Machines:
  • Lat pull down/seated raw: active hands looped exercise aid

• Cable and Pulley Machines: various handles and attachments
  • Solid handle and flexible strap
  • Active hands D-ring aid

• TRX System
  • Punchbag: gripping wrap with plastic tubing attached with gripping aid used as a glove

Watch this video explaining different equipment adaptations used in the gym for individuals with a spinal cord injury:

Tenodesis

Tenodesis function occurs when the wrist is extended and the fingers and thumb flex into the palm, and then when the wrist is flexed, the fingers and thumb open.  This function is used to facilitate grasp in people with tetraplegia who have wrist extension against gravity but no active finger function (C6 Motor Level). It is critical to gain a tenodesis function to enable task performance.  You can read more about this function here.

Gripping Aids

Watch this video presenting different use for gripping aids for individuals with spinal cord injury:

Precautions With Strength Training

The precautions that individuals with a spinal cord injury must consider when exercising include, but are not limited to the following:

• Falls Risk can be due to physically demanding activities which can lead to a fall, the safety of exercise equipment in the gym or outdoors, limited knowledge on fall prevention, physical impairments contributing to increased fall risk, eg., foot drop, and gym accessibility.
• Risk of Developing Pressure Ulcers due to time spent in a seated position while exercising.
• Alteration in Blood Pressure while exercising. Blood pressure can:
  • Drop (orthostatic hypotension) as a result of exercises performed above the heart level due to impaired muscle contracture assisting with blood flow to the heart and absence of sympathetic system activity at a level affecting the heart
  • Increase due to a radical sympathetic nervous system response to body noxious stimuli. It occurs with people with a spinal injury at the thoracic level (T6) and above. This issue is called autonomic dysreflexia and in addition to hypertension the symptoms may include headache, bradycardia, sweating and tingling sensation. You can read more about the sympathetic nervous system function here.

• Overuse Injury particularly affecting shoulders and wrists due to individuals with a spinal cord injury relying on the upper body for daily activities
• Body Temperature Dysregulation with an inability to regulate body temperature during exercises

Resources

Physical Activity Recall Assessment for People with Spinal Cord Injury (PARA-SCI)

• 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 the type, frequency, duration, and intensity of physical activity performed by individuals with a spinal cord injury who use a wheelchair as their primary mode of mobility.

ProACTIVE SCI Toolkit

• 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 is 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 cord injury.

Active Living Leaders

• Active Living Leaders is comprised of a series of peer-mentor training videos with the goal of helping people who would like to use the latest physical activity knowledge, sports 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 for Individuals with Spinal Cord Injury

• SCI-U Physical Activity Course is a collection of modularised training sessions.  It includes Modules on Living an Active Life, Ways to Get Fit, Overcoming Barriers and Reaching Your Goal.

SCI Action Canada Knowledge Mobilization Training Series

• SCI Action Canada's Knowledge Mobilization Training Series (KMTS) is a collection of modularised 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.