Wheel on Up, Pull on Down

Many common diseases such as Multiple sclerosis, Cerebral palsy, and Post-polio syndrome as well as traumatic brain and spinal cord injury, strokes, and tumors can lead to Paraplegia, or paralysis below the waist. While paraplegia of course is limiting, upper-body exercise and strength building is vital to establish an active, independent, healthy lifestyle. Exercise for those with spinal cord injuries and paralysis have also been shown to decrease the risk of developing many associated secondary conditions such as osteoporosis, cardiovascular disease, pressure ulcers, urinary tract infections, diabetes and arthritis. Exercising has also been shown to control pain, improve mental health, and maintain a healthy weight for those with limited mobility. However, the number of possible exercises are limited by a lack of accessible equipment and resources for people with limited mobility.

     Image 1. Diagram of muscle groups targeted by the lateral pull down machine.

An example of a piece of equipment that could increase upper body strength is a lateral pull down machine as shown above in Image 1. This machine is used in a sitting position and the user grasps the bar with palms facing forward and pulls the bar down toward their chest. This exercise targets the rhomboid major, latissimus dorsi muscles, located on the sides of your rib cage, the biceps, the lower trapezius, and the posterior deltoid in the back of the shoulder, all of which contribute to a stronger upper body.

Because this piece of equipment is composed of a bench and thigh stabilizer, someone in a wheelchair would not be able to use it to build their upper body strength without assistance to move out of their wheelchair. This is an issue for several pieces of upper body strengthening equipment. The question is, how could these pieces of equipment, the lateral pull up bar particularly, be altered to provide more independent access to those in wheelchairs without taking away from their current effectiveness? If this question were to be solved, perhaps it could lead those with limited mobility to feel more comfortable at community gyms and provide them with a means to exercise more independently.

Assumptions and Estimations:

  • Average arm length (young man with average height): 25 inches
  • Average armrest of wheelchairs: 30 inches
  • Height of resting bar combines the height of the armrest of the wheelchair and average arm length above, minus 5 inches to account for women as well
  • Average height of chairs: 19 inches
  • People perform pull down correctly and reach straight up to get bar
  • We are calculating force at hinge, each horizontal measurement to calculate moment is taken from this origin
  • Height of bench is 2 inches (measured at UD gym)
  • Height of stabilizer varies, but maximum would be 7 inches away (measured at UD gym)
  • Weight of bench is 5lbs
  • Weight of stabilizer is 1lb
  • Weight of each member is 6lbs

Image 2. Dimensions of standard Stack Loaded Lat Machine by Deltech Fitness, shows typical set up of the Lateral Pull Down Machine

As shown in Image 2 above, which is similar to most lateral pull down machines, the first aspect that requires adjustment is the dimensions. The width of the area where the wheelchair could pull in would have to be increased to a width greater than 32 inches in order to meet ADA standards for doorways. The bench and thigh stabilizer would also have to be adjusted so it could be cleared away from the area in which the wheelchair will sit. This machine can be altered by increasing the width to 33 inches and implementing a foldable bench/stabilizer mechanism that can be pushed up to the left or right side as shown below in Image 3a and 3b.

Image 3a (top) and 3b (bottom): 3a – Overlooking design of lateral pull down machine with updated dimensions that allow those in wheelchairs to access, as well as a removable bench that can be folded up. 3b – Image of bench and members in folded up position showing weight distribution centered around the hinge.

Using the following equation to determine moment on hinge:

|Mo| = (Force) * (Perpendicular distance)

and taking into account all assumptions and measurements used, the torque on the hinge can be calculated using the following values:

(Wbench*Distancebench) + (Wstabilizer *Distancestabilizer ) +(Wmember1 + Wmember2)*(Distancemembers)

(5lbs*20in)+(1lb*28in)+(12lb*9.5in) = 242 lb*in

The total torque on the hinge calculated is  242 pound inches. An off-set hinge made out of stainless can be used which provides a greater length on the ground to counter the force caused by the hanging bench. Reaching the bar is another issue for those in wheelchairs. To combat this issue, the wire can be lengthened so that the resting position of the bar should be 50 inches off the ground in order to provide access to those who are sitting without having to get up.

 This solution is assuming a standard size of wheelchairs which is used by the ADA when performing construction of doorways, however, wheelchair height and widths do change and not all will be able to fit in this gap. Exceptionally tall people may also suffer from these changes, as the wire length increase was done to help an average height or lower person. Those who are a lot taller may not gain full effectiveness of a pull down if they are starting lower than the top of their arm span reaches. This solution is indeed reasonable for those that have disabilities requiring the use of wheelchairs, however it is difficult to enact global changes such as this for development of equipment as the majority of users have the ability to use machines like this without these changes. Changes have to be encouraged by all to improve the accessibility to healthcare and exercise to all groups, even those who are marginalized. The value for the torque on the hinge makes sense, as it is carrying the full weight of the bench and the members that typically support the full weight of the user.

This solution may also need to be adjusted because sometimes gyms are limited in size and may not be interested in the fold up chair that could potentially take up more space than the original version. Coming back to the original question, this solution shows that equipment like the lateral pull down machine can be used for those who are disabled, and the development of this in gyms should be encouraged. Those with disabilities deserve the same opportunities to create a healthy lifestyle and feeling of community that comes with working out in a gym. The more independently they are able to do this, the more inclined they will be to continue. T changes in dimensions of the typical machine as well as the moveable bench allow that for those who typically would be unable to build their upper body strength in this way the ability to do so.

Additional Resources:






Just Keep Swimming (and checking your heart rate)

While exercise monitoring devices are made to deal with moisture and sweat, have you ever wondered how professional swimmers monitor their exercise while submerged? During the presentation on elevation masks in class I became intrigued about how complex it would be to monitor exercise in the water. This thought led me to the discovery of a swimming heart rate monitor in the form of a chest strap. Waterproof watches and dive computers that can also track heart rates exist on the market, however chest straps are known to provide a more accurate reading due to the proximity to the heart. But how could this design stay on, stay dry, and maintain accuracy? Let’s look into it.

Patent Title: Swimming Heart Rate Monitor
Patent Number: US20140336493 A1
Patent Filing Date: May 8, 2014
Patent Issue Date: Nov 13, 2014
Length for patent to issue: ~6 months
Inventors: Christopher J. Kulach, Timothy Vandermeiden, James K. Rooney, Rogelio A. Rivas, Phillip J.C. Spanswick
Assignee: Garmin Switzerland Gmbh
U.S. Classification: 600/390 (Belt or strap)
How Many Claims: 20

Figure 1. Front perspective view of swimming heart monitor containing electronics module at point 22 and length adjusting mechanisms at point 40.

The device shown in Figure 1 is comprised of two electrodes, two electrical connectors, an electronics module, and a water sealing feature. The adjustable strap, to be worn on the upper torso, is specifically designed to maintain function in chlorinated water, salt water, throughout intense body movement at high pressures. The electronic module processes electrical activity generated by the heart beat which is picked up by the electrodes. The electrical connectors on the external surface of the strap link the module to the electrodes. The connectors are enclosed by a water sealing feature, and attached to the removable electronic module which is in its own watertight housing. This module can be removed from the water-proof strap and used with other straps, in or out of water. This provides users with flexibility at a low cost. The user can monitor the heart rate in real time or upon completion of the exercise.

Figure 2. View of the module coupler and housing which are located on the external surface of the strap.

The strap itself, in length, is one third fabric elastic material and two thirds inelastic material, such as polyester, and is adjustable in length. The inelastic section is coated with a material, such as silicone, to increase the coefficient of static friction and prevent water flow between the skin and strap. The device creates a barrier from water, which would attenuate the amplitude of the heart signal, using two O-rings axially positioned on a post of the electrical connector. The electronics module is held in place by the coupler in Figure 2, also sealed by a water-proof housing.  Electrically conductive materials, such as conductive thermoplastic polyurethane (CTPU) or conductive silicone is used for the electrodes in order to maintain flexibility so contact with the skin remains constant. The module is to be placed around the sternum, with each electrode on either side. More electrodes could also be added to measure galvanic skin response, which tells the user information about hydration levels. The electronic connectors consist of a cylindrical post that attaches to an interlocking mechanism on the electronics module. The connectors also contain a first and second contact, which include an electrically conductive pin made from steel or copper that connects to the electronic component of the module. To combat skin impedance, filtering techniques such as the Lease-Means Square Algorithm are used to calculate the heart rate. The electronic module contains a battery, signal amplifiers, processing elements, memory elements, transmitters, and antennas that allow the data to be communicated in several ways. Certain models may also contain inertial sensors such as accelerometers or gyroscopes, so the device can be personalized to the user’s needs.

This patent referred to wrist monitors, headbands, and belts with similar capabilities, some for aquatic use and some for land. It is ideal out of this group of ideas because of its proximity to the heart which typically results in more accurate signals. Compared to other chest straps, it is ideal for aquatic environments because of the proportions of elasticity of the strap. This provides a snugness that is designed not to fold on itself or slip away from the heart when wet, and the materials for the electrodes are designed similarly. I found it particularly impressive that the device is multifunctional and adaptable beyond heart rate monitoring.

Physical therapy clinics would be a great target audience because of this, as they could buy a few different models and adapt per patient as necessary, saving them both money and space. This technology is also useful for competitive swimmers and triathletes. For those training, it allows them to reach their specific training goals, whether they want to hit the recovery, aerobic, or lactate threshold training zone. For those in rehab, where a physical therapist might want to ensure they are not surpassing a certain heart rate, this device would be ideal and potentially more accurate than a heart rate monitor worn on the risk. My question about underwater exercise monitoring was answered by this patent as well as the other related products that are being developed, and it’s interesting to think about what this kind of technology might lead to in the future of rehab and water-sports.

Nah Coach, I don’t have to stretch.

Ever wondered if those pre- and post- workout sessions really make a difference in your daily exercise regimen? It is commonly believed that stretching prior to and following a workout will decrease the likelihood of injury, minimize post workout pain, and increase performance. However, other athletes and trainers believe that stretching has no impact on these factors and can even decrease strength and performance. But what are the facts?

Figure 1. Examples of active and passive/static and dynamic stretching.

There are several subgroups of stretching but I will focus on performance results with regards to the two most well researched types: static versus dynamic. Each stretch can be done actively or passively, where active stretching is when you contract the muscle in opposition to the one you want to stretch and passive uses an external force such as a strap, the force of your body weight, or gravity. Each type of stretching, shown above, has been shown to impact exercise in different ways. Let’s start with the most frequently used type, static stretching, where a person slowly moves muscles until they reach the brink of pain and hold that position for 20-30 seconds.

Static stretching has been compared to continuously stretching a rubber band. Immediately after stretching the rubber band, the band remains limp as it contracts slowly back into its original form, similarly to the behavior of a muscle. It seems unrealistic to expect a maximum amount of contraction and force immediately after stretching your muscle. In more physiological terms, the loss of muscular stiffness caused by static stretching results in an increase in length of sarcomeres in each muscle fiber, decreases contact between actin and myosin, and therefore decreases the force produced (Shrier, 2004; Kokhonen et al., 2004).

Figure 2. Actin and myosin movement in relaxed muscle versus contracted muscle. The less contact between actin and myosin, the less force produced.

One study by Fletcher and Jones (2004) on 97 male rugby union players showed a significant decrease in sprint times for the passive static stretch group. This could be due the mechanical impact of stretching on the muscle, kinematic differences, or neural inhibition which decreases the neural drive to muscle. Dynamic stretching focuses on moving through a range of motion repeatedly and mimics motion that will occur during exercise. Fletcher and Jones’ (2004) study showed more beneficial performance results from active dynamic stretching prior to sprinting though. The active dynamic stretch group of rugby players improved their sprint times significantly.

These results could be explained by information in a systematic review of studies on stretching and exercise by McGowan et al. (2015). This review showed that dynamic stretching increases the temperature of the muscle more than static stretching. This increase in temperature activated an increase in muscle metabolism, elevated oxygen uptake, and increased the power output of the muscle. Another study by Gray et al. (2008) showed a correlation between increased muscle temperature and faster ATP turnover, caused by an elevated rate of creatinine phosphate utilization and H+ accumulation. The elevated muscle temperature also resulted in short term (~2 minute) increase in anaerobic glycolysis and muscle glycogenolysis. These physiological responses, in theory, would result in greater power production during sprint and sustained high-intensity exercise, however high quality research results on this topic are limited.

Several literature reviews regarding this topic exist, but compiling results from hundreds of varying studies makes it difficult to normalize the results. Several reviews analyzed results that were not statistically significant, skewing the review results. By looking at the methods researchers used to gather and compile data and at the sources they cited, I was able to identify the sources where results were significant and relevant. The review also covered studies on a span of sports from swimming, to sprinting, to jumping, all which are impacted very differently by stretching, which makes the conclusions for these reviews far reaching statements. When more studies are done within each of these sports, reviews that group together specific events and exercises will provide more beneficial results.

When looking at the impact of stretching on pain, several papers used self-reported ratings of pain to measure differences. In those studies the results did not show a significant difference between ratings from groups that stretched and controls. Self-reported measurements of pain contain bias which makes them difficult to compare between groups of people. Some papers overcame bias by observing differences in delayed muscle soreness by measuring creatine kinase levels, a commonly used marker for muscle damage. One experiment by Buroker and Schwane (1989) showed no significant difference in creatine kinase levels from stretching post-exercise. Very few studies are done solely to measure the effect of post-exercise stretching on soreness and risk of injury so it is difficult to differentiate these results from the pre-exercise stretching.

Keeping these biases and knowledge gaps in mind when considering the results of these papers, it is plausible that for the majority of exercises, dynamic stretching can positively impact your performance. This is largely due to the fact that it increases the core body temperature and targets activity in specific muscles that will be used instead of just stretching them. Static stretches prior to a workout seem to have no impact or a negative impact on performance since the muscle needs time to recover and regain stiffness before use. Personally, this would convince me to do some dynamic stretches before my next run rather than static stretches. While it differs from sport to sport, dynamic stretching appears to be the ideal pre-exercise stretch to optimize performance.

Recommended Further Reading:

1. Blahnik, Jay. Full-Body Flexibility, Second Edition. Available at: http://www.humankinetics.com/excerpts/excerpts/types-of-stretches

2. Sifferlin, Alexandra. Why Stretching May Not Help Before Exercise. (April 08, 2013) Available from: http://healthland.time.com/2013/04/08/why-stretching-may-not-help-before-exercise/

3. Shrier, Ian. Sports Med (2004) 14:267-273. Available from: http://www.elitetrack.com/article_files/stretchingreview.pdf

4. Kokkonen,  J.,  Nelson,  Α.  G.,  Cornwell,  Α.  (1998). Research Quarterly for Exercise and Sport. 69 (4): 411-415. Available from: https://www.ncbi.nlm.nih.gov/pubmed/9864760

5. Fletcher, IM, Jones, B. J Strength and Condition Research. (2004) 18(4), 885-888. Available at: http://staps.nantes.free.fr/L3/entrainement/etirements/THE%20EFFECT%20OF%20DIFFERENT%20WARM-UP%20STRETCH.pdf

6. McGowan, C.J., Pyne, D.B., Thompson, K.G. et al. Sports Med (2015) 45: 1523. Available at: https://link-springer-com.udel.idm.oclc.org/article/10.1007%2Fs40279-015-0376-x

7. Gray, SR, Soderlund, K, Ferguson, RA. J Sports Sci. (2008) 26(7):701:7. Available at: https://www-ncbi-nlm-nih-gov.udel.idm.oclc.org/pubmed/18409101?dopt=Abstract

8. Buroker, KC, Schwane, JA. The Physician and Sportsmedicine (1989) 17(6): 65-83. Available from: http://www.tandfonline.com/doi/citedby/10.1080/00913847.1989.11709806?scroll=top&needAccess=true