Fatigue Induced by Overground Wheelchair Propulsion in Persons With a Spinal Cord Injury: Upper Limb Saving or Straining?
Condition: Spinal Cord Injuries; Fatigue; Muscle, Heart
MeSH terms: Spinal Cord Injuries; Fatigue; Wounds and Injuries
Study type: Observational

Summary: 
      What are the implications of wheelchair propulsion-induced fatigue for the development of
      shoulder pain and how can this knowledge improve prevention programs?

      With this project, the "Shoulder Health and Mobility group" of the Swiss Paraplegic Research
      in Nottwil (Switzerland) wants to investigate how fatigue during wheelchair propulsion
      affects risk factors for shoulder pain of persons with a spinal cord injury (SCI). The
      investigators want to find out how the handrim wheelchair propulsion technique changes with
      fatigue and want to define persons who are susceptible to fatigue.

      Getting life back after a SCI will most likely occur with the help of a wheelchair, whether
      it is at the beginning of rehabilitation or throughout further life. Gaining back mobility
      and participation in social life is important, also because of the multiple positive effects
      of physical activity on person's health and self-esteem, preventing several chronic diseases.
      Therefore, it is needed to try to stay away from shoulder injuries. Since the shoulder is
      very mobile and thus unstable, the joint is at increased risk for injuries. This is reflected
      in the high amount of persons with a SCI having shoulder pain (between 30 to 70 %). Once pain
      or an injury occurred, it is hard to recover, as so far no effective treatment is available.
      Several factors as gender, weight, age, level and completeness of the SCI, movement patterns
      and muscle strength were found to be related with injury and pain. However, it is currently
      not well understood what exactly causes shoulder injuries.

      Handrim wheelchair propulsion is an inefficient mode of propulsion and asks a lot of demands
      to the upper body. Because of the inefficient movement and the shoulder being prone to
      injuries, wheelchair propulsion has a high chance of inducing shoulder injuries and pain.
      Propelling with a technique minimizing the loads on the shoulders and improving the capacity
      to perform these movements (as increasing muscle strength) is of utmost importance as these
      factors can be modified by training. Previous intervention programs have learned wheelchair
      users to propel with long and smooth strokes aiming to reduce the loads. Although someone
      might be aware of the recommended techniques and can apply them, propulsion technique might
      change with fatigue and could become less optimal. A similar phenomena happens for example in
      landing strategies from a jump. In a fresh state, persons will try to have a stable landing
      reducing the impact on the lower limbs. With fatigue, however, there will be a tendency to
      forget about the proper landing technique which on its turn can increase the risk of
      injuries. This was suggested to be one of the reasons why there is an increased prevalence of
      injuries towards the end of a game. So far, it is unclear how fatigue alters propulsion
      technique and how these changes are related with an increased risk of shoulder pain.

      Tis project aims to achieve the goals by investigating how very strenuous wheelchair
      propulsion (fatigue intervention) of 15 minutes alters the propulsion technique of 50 persons
      with a SCI. All participants will perform the fatigue protocol in the movement analysis lab
      at the Swiss Paraplegic Research. During the protocol, participants will be requested to
      perform as many 8 loops as possible with their wheelchairs, including starts, stops, and
      right and left turns. Before and after the protocol, movement patterns, muscle usage and
      loads during wheelchair propulsion and the characteristics of the shoulder muscle tendons
      during rest will be assessed. Furthermore, the person's characteristics, such as weight, age,
      gender, time since injury, injury level, health conditions, use of medication, muscle
      strength and activity levels will be assessed. All these factors might be associated with the
      susceptibility to fatigue.

      To answer our questions, we will first compare the propulsion technique (movement patterns,
      loads, and muscle usage) before and after the protocol to investigate the direct effect of
      fatigue. Secondly, we will investigate the association of negative changes in tendon
      appearance (which has been related to injury) with the changes in the propulsion technique to
      investigate the implications of acute changes that might increase the risk of injury. Finally
      we will run a model including all variables to determine which person's characteristics are
      associated with an increased susceptibility to fatigue.

      The results will be highly relevant as it will give answers about the content, the aims and
      the target population of prevention programs for shoulder injury, aiming to improve mobility,
      participation, and quality of life in persons with SCI.
    

Detailed description: 
      Background and rationale:

      Wheelchairs are the most important assistive devices used by persons with a spinal cord
      injury (SCI). A Danish study reported for example that 83.5% of 236 persons used a manual
      wheelchair and 27% a powered wheelchair, some of which used both a manual and an electrical
      wheelchair. The repetitive nature of wheelchair propulsion in combination with the shoulder
      being prone to injuries results in a high prevalence of persons with a SCI having shoulder
      pain. Several factors have been associated with shoulder pain but exact pathways remain
      unclear. In order to improve injury prevention which would have a significant effect on
      shoulder pain, it is important to focus on biomechanical and neuromuscular risk factors
      modifiable by training. Fatigue could have a negative effect on propulsion mechanics further
      increasing the risk of injury. Previous studies have induced fatigue by interventions on a
      treadmill or with an ergometer. However, it is important to investigate functional fatigue,
      as the effect of fatigue is task dependent. To date there is no clear understanding of the
      effect of functional fatigue on biomechanical and neuromuscular risk factors in persons with
      SCI during wheelchair propulsion.

      Objectives:

      Main objective: What is the role of muscle fatigue in altering neuromusculoskeletal and
      movement body functions and structures related to shoulder pain in persons with SCI? Aim1: To
      define how muscle fatigue induced by wheelchair propulsion changes biomechanical and
      neuromuscular risk factors of shoulder injuries, leading to shoulder pain, in persons with
      SCI.

      Aim 2: To evaluate how changes in propulsion biomechanics due to propulsion-induced fatigue
      are associated with changes in tendon appearance related to tendinopathy, in persons with
      SCI.

      Aim 3: To identify predictor variables (e.g., activity levels and muscle strength) for
      persons with SCI who are susceptible to wheelchair propulsion-induced fatigue.

      Study design: Repeated measures within subject design

      For this study, 50 participants will be recruited via the Swiss Spinal Cord Injury Cohort
      study database. The number of 48 participants was calculated based on a sample-size
      estimation from a study investigating a high-intensity wheelchair propulsion activity that
      found that echogenicity ratio changed significantly from 1.97 ± 0.74 to 1.73 ± 0.56 (p=0.038)
      (after the intense wheelchair propulsion activity. To observe this change of 0.24 difference
      in echogenicity ratio of the biceps tendon at 80% statistical power and alpha=0.05, 48
      participants are needed. In order to take into account drop-out and missing data 50
      participants will be recruited. All participants will meet the defined inclusion criteria and
      excluded when meeting the exclusion criteria.

      Data collection:

      Participants will be tested during one session of four hours after they have read and signed
      the informed consent. During the testing session the following measurements will be
      performed:

      Participant's characteristics and activity levels: Socio-demographic variables, injury
      characteristics, presence of contractures and spasticity will be defined with a general
      questionnaire. Furthermore, activity levels will be defined with the Physical Activity Scale
      for Individuals with Physical Disabilities (PASIPD).

      Participants weight will be measured.

      Quantitative ultrasound pre-fatigue: Ultrasound measurements of the biceps brachii and
      supraspinatus tendon at rest will be collected with Quantitative Ultrasound Protocols (QUS).
      This technique has been used previously and has proven strong reliability and validity for
      measures of shoulder pain and tendinopathy. More specifically, for the biceps tendon
      longitudinal image, participants will be positioned with their non-dominant arm flexed 90˚ at
      the elbow and their wrist resting on the ipsilateral thigh. Images will be taken so that the
      fibres are aligned perpendicular to the transducer which optimises the quantification of
      fibre alignment and tendon thickness. In order to mark the skin location of the pre-fatigue
      measurement, a steel reference marker will be taped to the skin at the distal end of the
      transducer. The distinct interference pattern created by the marker at the top of the images
      is used to define the region of interest (ROI) upon which the computations are performed. For
      the supraspinatus transverse image, participants will be positioned with their non-dominant
      palm placed on the lower back, shoulder extended, and elbow flexed posteriorly. The steel
      marker is now taped to the skin at the proximal end of the transducer and the widest part of
      the tendon is imaged. The specific positions optimize image quality and repeatability of the
      imaging protocol. Furthermore, three consecutive measurements of the acromio-humeral distance
      of the non-dominant hand will be collected under an unloaded and loaded conditions (during
      push up in wheelchair, once without further instructions and once with the instruction of
      retracting the shoulders) as has been done previously.

      The same trained investigator will perform all ultrasound measurements.

      Maximum sprint and strength test: A 15m over ground sprint test will be performed to define
      anaerobic work capacity. Furthermore a maximum isometric forward push against resistance on
      the wheelchair will be performed to measure maximal strength.These tests have been used
      previously. During both tests, external forces will be collected at 100 Hz with the
      SmartWheel. The 15m sprint aims to define the anaerobic work capacity. The participants will
      be required to propel as fast as possible from one cone to another standing 15 meters apart
      which will result in an outcome of the maximum unilateral power output. For the isometric
      maximum push, the wheelchair with SmartWheel will be connected via a rope to a force
      transducer and a wall. The participant will be requested to push as hard as possible for 5
      seconds with the hands on top of the handrim to measure the maximum applied force.

      Wheelchair propulsion pre-fatigue: The participant will be requested to propel his/her
      wheelchair on the treadmill for two trials of 90 seconds at two power output conditions
      (intermediate and hard). During the trials, 3D kinematics of the upper extremity, 3D kinetics
      applied to the handrim of the wheelchair and muscle activation of muscles active during
      wheelchair propulsion will be collected.

      Fatigue protocol: The figure 8 protocol (fatigue intervention) requires the participants to
      propel three times as many laps as possible for four minutes each. Every bout of four minutes
      is separated by 90 seconds of rest. Each lap consists of a right and left turn and two
      complete stops after half a lap. Measurements during the protocol include the Rate of
      Perceived Exertion (RPE) scale, heart rate, and propulsion kinetics.

      Wheelchair propulsion and Quantitative ultrasound post-fatigue: The same measurements as in
      the pre-fatigue tests will be performed.

      Statistical considerations:

      Aim 1: To investigate the effect of muscle fatigue induced by wheelchair propulsion on
      biomechanical and neuromuscular risk factors of shoulder injuries, leading to shoulder pain,
      in persons with SCI.

      Hypothesis 1: Muscle fatigue induced by wheelchair propulsion will result in significant
      changes in biomechanical and neuromuscular risk factors related to shoulder pathology.

      Dependent variables of interest are stroke frequency, glenohumeral contact force, net joint
      moments, kinematic and normalised muscle forces during wheelchair propulsion, tendon
      appearance of the m. biceps brachii and m. supraspinatus, and acromio-humeral distance. A
      statistical parametric mapping (SPM) one way repeated measures ANOVA will be used to assess
      meaningful variations across time for each continuous variable during wheelchair propulsion
      (alpha=0.05).

      Aim 2: To determine the relation between changes in propulsion biomechanics and changes in
      tendon appearance related to tendinopathy post-fatigue, in persons with SCI.

      Hypothesis 2: There will be a positive association between changes in propulsion biomechanics
      and changes in tendon appearance of the m.biceps and m.supraspinatus when controlling for
      sex, level and completeness of injury, health conditions, range of motion and weight.

      Independent variables will be changes in propulsion biomechanics that significantly changed
      after the fatigue protocol and dependent variables will include changes in tendon appearance
      of the m.biceps and m.supraspinatus. Covariates will be sex, level and completeness of
      injury, health conditions (spasticity and contractures), range of motion and weight.
      Multivariable linear regression analysis will be used to test the hypothesis

      Aim 3: To investigate the relation of the susceptibility of fatigue and person's
      characteristics (activity levels and muscle strength), in persons with SCI.

      Hypothesis 3: There will be a negative association between changes in propulsion biomechanics
      (including stroke frequency, scapular kinematics and glenohumeral contact force) and both
      activity levels and muscle strength, when controlling for sex, level and completeness of
      injury, health conditions (spasticity and contractures), range of motion and weight.

      Independent variables will be propulsion biomechanics that significantly changed after the
      fatigue protocol and dependent variables will include physical activity levels and muscle
      strength. Covariates will be sex, level and completeness of injury, health conditions
      (spasticity and contractures), range of motion and weight. Multivariable linear regression
      analysis will be used to test the hypothesis.
    

Intervention name(s): Fatigue protocol
Intervention type(s): Behavioral
Intervention description(s): The figure 8 protocol (fatigue intervention) requires the participants to propel three times as many laps as possible for four minutes each with their wheelchair. The protocol has been developed and used previously. Every bout of four minutes is separated by 90 seconds of rest. Each lap consists of a right and left turn and two complete stops after half a lap. Measurements during the protocol include the Rate of Perceived Exertion (RPE) scale, heart rate, and propulsion kinetics.
Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        This study will investigate healthy individuals with a SCI. Suitable participants will be
        identified based on the SwiSCI community survey (EKNZ registration number 1008). Suitable
        persons will be selected based on age (18-65 years), lesion level of SCI (paraplegia),
        language (German and French), time since injury, and use of wheelchair for daily
        activities. These persons will be contacted by letter and asked whether they are interested
        in participating in the study. After initial screening, further selection will be done
        using a questionnaire and further contact will be done by either telephone, e-mail or
        written letter (participants preference).
      
Keywords: Wheelchair propulsion; Shoulder; Biomechanics