Strength Training in Neurological Rehabilitation


Strength Training in Evidence

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Paresis (muscle weakness) is a is a key physical impairment in neurological conditions limiting mobility[1]. Resistance training has been found to improve muscle strength[2] and functional performance when added to functional exercises[3].

A systematic review by Kjølhede in 2012 reported strong evidence regarding progressive resistance training on muscle strength for people with Multiple Sclerosis[4]. Progressive resistance exercises were strongly recommended by the Australian Stroke Foundation guidelines (2017) and the AHA guidelines (2010), however, the optimal strengthening approach is still unknown[1]. Different systematic reviews[4][5][6][7][8] demonstrated improvement in strength following resistance training but showed limited impact on walking parameters[9] Williams et al [9] investigated task specificity of strength training for walking in neurological conditions, this systematic review found quadriceps and hamstrings exercises to be the most commonly used exercises in neurological rehabilitation.

Biomechanics of Gait

A good understanding of gait parameters is needed to prescribe proper exercises for walking. Muscle recruitment and speed influence walking mechanics across hip, knee and ankle joints[10]. A minimal level of strength is required in all muscles to generate power for walking, however, not all muscles are recruited equally.

Three key events are important for power generation during the walking cycle:

  1. Hip extensor power generation at Initial Contact
  2. Ankle plantar flexion power generation at push-off (terminal stance)
  3. Hip flexor power generation at toe-off to accelerate the leg through the swing phase

At the knee joint, muscles generate force for power absorption:

  • Knee extensors at terminal stance
  • Knee flexors at terminal swing to decelerated the leg.

At the stance phase, the main power is generated at the ankle, when the plantar flexor generates power at terminal stance for push off. A study analysed the power generated at the ankle joint and found that Achilles tendon produced the highest peak of force.[11] Stance phase makes up about 0.6 seconds of the gait cycle. Push off represents about 0.15 seconds- this is when the achilles tendon is producing most of the power. Strength training can increase the muscle-tendon strength but not the power needed for the push off.

Is It Just About Strength?

Strength training trains the ability to overcome resistance where you focus on moving as much weight as possible for the given number of repetition.[12]

Progressive Resistance Exercises (PRE) is a form of power training. Power Training focusses on overcoming resistance but also focusses on the ability to overcome the resistance in the shortest period of time[12]. PRE are considered the best method for improving force production and muscle hypertrophy. Changing resistance constantly is the key to improve strength[1]. Heavy resistance training improves strength whereas ballistic (lighter loads and high repetitions) training improves power generation[1].

Speed is another factor that influences gait mechanics as muscle power generation during walking occurs at high angular velocities. Applying the principals of ballistic training at a targeted speed at the ankle joint can be the key to improve walking [1].

A 2017 study[13] evaluated the effect of functional high-velocity resistance training (power-training) to improve muscle strength and walking capacity of children with Cerebral Palsy. Significant improvement was reported in the muscle power sprint test, 1-minute walk test (1MWT), 10-m shuttle run test (SRT), gross motor function, isometric strength of lower-limb muscles and dynamic ankle plantar flexor strength reflecting improvement on walking capacity.

Seated leg press was performed with and without a jump in a single testing session by Williams[14]. A 70% increase in concentric velocity was reported in the ballistic exercise condition.

[15]

In Williams et al systematic review[9], most studies did not include exercises relating to all three main power events important for walking. Instead, strength testing and strengthening exercises were prioritised for the knee extensors and flexors, despite their minor role in normal gait cycle.

Clinical Applications

Considerations for exercise prescriptions:

  • Power training is recommended over conventional strength/resistance training with considerations to gait biomechanics.
  • Exercises should be performed with speed
  • Exercise has to be specific to the muscles that generate the power (ankle plantar flexor). If the patient is unable to isolate the right muscle, apply some modifications to allow for proper performance.

Task specificity principals based on ACSM guidelines[16]:

  • Role of the muscle
  • Action of the muscle
  • Type of contraction
  • Active range and segmental alignment
  • Load
  • Speed of movement

Progression Principals:

  • Progressive muscle overload
  • Greater intensity
  • Periodisation
  • Increasing total repetition & training volume
  • Increasing the speed of movement
  • Reduce rest
  • Hypertrophy
  • Muscle Endurance
  • Sports application

In neurological conditions, proximal compensations greater forces were observed in the hip flexors and extensors[17]. Power training can reverse these proximal compensations[18]. Despite being highly important for standing up from a chair and stairs[19], Quadriceps strengthening is not the key for better walking.

Example exercises

To improve walking and gait focus on ballistic or fast exercises, and particularly target the calf because it is so important for walking. For example, if you have no resources or are in a home environment, it would be better to do a quick 'calf drop' exercise rather than a controlled calf raise – i.e. raise up onto the toes and then quickly drop down and push up again. Or with access to a mini-trampet the exercise could involve bouncing between alternate heel raises demonstrated in the video below.

Additional ideas for appropriate exercises.

References

  1. 1.0 1.1 1.2 1.3 1.4 Williams G, Strength Training in Neurological Rehabilitation Course, Physioplus 2019
  2. Royal College of Physicians Intercollegiate Stroke Working Party. National Clinical Guidelines for Stroke. 3rd ed. London,UK: Royal College of Physicians; 2008.
  3. Olivetti L, Schurr K, Sherrington C, et al. A novel weightbearing strengthening program during rehabilitation of older people is feasible and improves standing up more than a nonweight-bearing strengthening program: a randomised trial.Aust J Physiother. 2007:53:147-153.
  4. 4.0 4.1 Kjølhede T, Vissing K, Dalgas U. Multiple sclerosis and progressive resistance training: a systematic review. Multiple Sclerosis Journal. 2012 Sep;18(9):1215-28.
  5. Ada L, Dorsch S, Canning CG. Strengthening interventions increase strength and improve activity after stroke: a systematic review. Australian Journal of Physiotherapy. 2006 Jan 1;52(4):241-8.
  6. Morris SL, Dodd KJ, Morris ME. Outcomes of progressive resistance strength training following stroke: a systematic review. Clinical rehabilitation. 2004 Feb;18(1):27-39.
  7. Dodd KJ, Taylor NF, Damiano DL. A systematic review of the effectiveness of strength-training programs for people with cerebral palsy. Archives of physical medicine and rehabilitation. 2002 Aug 1;83(8):1157-64.
  8. Van De Port IG, Wood-Dauphinee S, Lindeman E, Kwakkel G. Effects of exercise training programs on walking competency after stroke: a systematic review. American Journal of Physical Medicine & Rehabilitation. 2007 Nov 1;86(11):935-51.
  9. 9.0 9.1 9.2 Williams G, Kahn M, Randall A. Strength training for walking in neurologic rehabilitation is not task specific: a focused review. American journal of physical medicine & rehabilitation. 2014 Jun 1;93(6):511-22.
  10. Schwartz MH, Rozumalski A, Trost JP. The effect of walking speed on the gait of typically developing children. Journal of biomechanics. 2008 Jan 1;41(8):1639-50.
  11. Sawicki GS, Lewis CL, Ferris DP. It pays to have a spring in your step. Exercise and sport sciences reviews. 2009 Jul;37(3):130.
  12. 12.0 12.1 Christian Bosse Power Training vs Strength Training – what is the difference between Strength Training and Power Training? Available from: https://christianbosse.com/power-training-vs-strength-training-what-is-the-difference/ (last accessed 7.2.2020)
  13. Van Vulpen LF, De Groot S, Rameckers E, Becher JG, Dallmeijer AJ. Improved walking capacity and muscle strength after functional power-training in young children with cerebral palsy. Neurorehabilitation and neural repair. 2017 Sep;31(9):827-41.
  14. Williams G, Clark RA, Hansson J, Paterson K. Feasibility of ballistic strengthening exercises in neurologic rehabilitation. American journal of physical medicine & rehabilitation. 2014 Sep 1;93(9):828-33.
  15. Leg press jump squats . Available from: https://www.youtube.com/watch?v=pOZj64mRN8Q
  16. American College of Sports Medicine. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Medicine and science in sports and exercise. 2009 Mar;41(3):687. Available from:https://www.ncbi.nlm.nih.gov/pubmed/19204579 (last accessed 7.2.2020)
  17. Williams G, Morris ME, Schache A, McCrory P. Observational gait analysis in traumatic brain injury: Accuracy of clinical judgment. Gait & posture. 2009 Apr 1;29(3):454-9.
  18. Williams G, Schache AG. The distribution of positive work and power generation amongst the lower-limb joints during walking normalises following recovery from traumatic brain injury. Gait & posture. 2016 Jan 1;43:265-9.
  19. Canning CG, Shepherd RB, Carr JH, Alison JA, Wade L, White A. A randomized controlled trial of the effects of intensive sit-to-stand training after recent traumatic brain injury on sit-to-stand performance. Clinical rehabilitation. 2003 Jun;17(4):355-62.