Shoulder Health and Mobility

Several factors are involved in the development of shoulder pain, but the repetitive load of wheelchair propulsion is seen as one of the major risk factors. However, mobility devices such as the wheelchair are important since they support people with spinal cord injury (SCI) to live an independent life. Therefore, alternative or additional mobility devices to the manual handrim wheelchair should be considered. Since upper extremity mobility is usually the only means of physical exercise for SCI individuals, a manual device is preferable to maintain regular physical activity.

The handbike is one of these alternative mobility devices. It is increasingly used for commuting, recreation and sports. Compared to handrim wheelchair propulsion, the usage of a handbike is physiologically (heart rate, breathing, energy expenditure) more efficient and less straining. Whether also the mechanical load at the shoulder is lower than during wheelchair propulsion has not been investigated.

The focus of this project was on the biophysical benefits of handcycling in order to investigate the general assumption that the handcycle is indeed a good device for the prevention of shoulder problems. Additionally, we studied the handcycle-user interface. This will allow for practical advice on how to best adjust the handcycle to its user in order to further reduce the load on the shoulder joint.

Results

The figure below shows the difference in shoulder load between handcycling and wheelchair propulsion. Glenohumeral contact force is the force with which the shoulder joint is compressed during the propulsion. The compression is a result of the exerted force by the hand and of the contractions of all muscles around the shoulder to perform the required movement and to stabilize the shoulder joint while doing so. (For example, 10 Newton (N) is the force needed to hold a mass of 1 kg against gravity).

From the graphs it can be concluded that the load on the shoulder is much lower for handcycling.

30% to 70% of individuals with spinal cord injury (SCI) suffer from shoulder pain. This has an enormous impact on functioning, independence and quality of life. The treatment is often unsatisfying and the pain problem remains.

Early diagnosis and early intervention of shoulder problems can markedly reduce the impact of shoulder pain. Although the exact mechanism remains unclear, several known factors contribute to the development of shoulder pain.

One of these factors is the mechanical load on the shoulder in relation to its capacity, for instance: how much force is needed to propel a wheelchair, and what is the maximum propelling force an individual can deliver? The lower the maximum, the sooner muscles will be fatigued. Improving the capacity to a sufficient level will have a positive effect on the prevention of shoulder pain.

It is also known that movement patterns can change due to fatigue, by a change in the activation or coordination of muscles. A less optimal movement pattern during wheelchair propulsion, a weight relief lift or a transfer can increase the risk of shoulder pain. Movement patterns are measured in our motion lab.

Finally, prolonged activities can also lead to tissue change, for instance thickness and appearance of biceps tendon. Such changes in tendon thickness can be observed and quantified by Ultrasound imaging, not directly during wheelchair propulsion, but shortly after a fatiguing exercise, or during a weight relief lift.

How these mentioned changes, due to fatigue, are related to wheelchair propulsion and mechanical load at the shoulder is not known. It is, however, required information for the further development of training and prevention programs.

Fundamental research is required to gain insight in working mechanisms of upper extremity function, for which controlled conditions in motion labs are essential.

In addition questionnaires are used to gather information on lived experience from larger groups of participants.

Both approaches aim at extracting information from real life, and after analysis and discussion, generalize conclusions back to real life. Both approaches are, however, also just snapshots of what happens in real-life.

With the rapid technological development in the past two decades a third approach comes into reach. A broad variety of wearable sensors and smartphones might enable the desired longitudinal monitoring of upper extremity functioning in real life, to obtain an overview of real life demands and clarify dose-response relations among:

• physical activities,
• biomechanical load on the upper extremity, up to the level of musculoskeletal modelling,
• long-term effect on tissue change,
• performance of function.

Besides, these non-intervening, discrete and wearable devices can potentially also be used as feedback devices, during rehabilitation or after discharge in real life in order to:

• optimize or maintain optimal wheelchair propulsion style,
• indicate over- or underuse with respect to individual capacity,
• support or coach in adherence to «healthy» performance.

To enable the development of such an upper extremity quality management system, we focus our research on:

• development of methods and algorithms (e.g. to estimate biomechanical load in real life),
• testing usability of equipment (e.g. Smart Watches, Internet of Things modules) to enable large scale measurement in real life,
• creation of safe and adequate infrastructure (where to store and process data, who can access data).