Tag: rehabilitation

Walk [Under] Water: The Benefits of Underwater Running

Just because you can’t walk on water doesn’t mean you shouldn’t run under it!

Aqua-jogging. Hydro-running. Water-treadmills. Have you ever heard some combination of these terms and wondered what the hype is?

Running underwater offers benefits for people throughout their fitness journey. Underwater running has proven useful for a variety of focuses, including recovery after injury, cross training, and even improved gait. This article includes a video showing a Runner’s World coach tries out a Hydrotrack and discusses some of the benefits!

So, why does it work?

Three basic water properties: hydrostatic pressure, buoyancy, and viscosity.

Hydrostatic pressure is the force that the water exerts on a submerged point. Hydrostatic pressure acts all around the point. However, since hydrostatic pressure is proportional to the weight of liquid above the point, it increases with increased water depth. This means that your feet would experience greater hydrostatic pressures than your knees. While running, this pressure helps support your body and decrease impact forces. In addition to helping prevent injuries through a decreased risk of falling, it also helps decrease swelling and promote cardiovascular health. This article talks about the specifics of pressure with swelling and the cardiovascular system.

Diagram showing hydrostatic forces. Magnitude of the hydrostatic force is larger as it goes deeper below the surface.
Hydrostatic pressure acts on all sides of a point. The pressure increases with depth. Created in Microsoft PowerPoint.

Buoyancy is the hydrostatic force applied to an object with volume (rather than just a point). Since they are at the same depth, all the horizontal forces cancel out. Since the bottom of the object is deeper than the top, the net buoyant force on the object pushes up. The difference between the buoyant force and the weight of the object submerged determines if the object will rise, sink, or stay in place. Thus, the more submerged a person is, the more of their weight is supported. This research article explains how this support can help make gait analysis more effective to further prevent injury. When water reaches the person’s navel, 50% of their weight is supported. This weight bearing capability of water decreases forces on joints and can even help improve range of motion. This allows physical therapy to begin sooner and, overall, take less time out of the patient’s normal routine. This allows shorter rehabilitation times without sacrificing quality of care or recovery.


Diagrams showing how the hydrostatic force varies around the submerged object due to depth. The side forces cancel out at equal depth leaving a net buoyant force acting upward against the downward force of the object weight.
Buoyant forces cancel out on the sides leading to the second image showing the net buoyant force and the weight of the object. Created in Microsoft PowerPoint.

Viscosity is a fluid property that affects the resistance that an object encounters during motion. In the case of underwater running, viscosity explains why you move significantly slower in water than on land. It also can offer resistance up to 15 times the amount of resistance on land. Forcing your limbs through the water strengthens muscles that are not typically used out of the water and even burns more calories!

As noted above, viscosity can help strengthen muscles as shown in this study on deep water running (DWR) in a community of elderly women shows how viscosity affects overall strength training. It showed that the women who participated in DWR increased their muscle strength (measured through power) and performed better in various tests, including ones that involved sitting down and getting up. The study showed that deep water running helped to mitigate some of the negative muscular effects of aging.

Overall, running underwater offers some great benefits. The basic properties of water (hydrostatic pressure, buoyancy, and viscosity) provide scientific background for why hydro-running provides benefits for all.








Back Against the (John) Wall

What would you do if you went to the doctor expecting to get back to work, only to be told you might not ever be able to go back to work again?

According to ESPN, on February 4, John Wall visited his doctor regarding an infection in his heel after a previous operation. The doctor checked the infection, but upon further analysis, realized that Wall had suffered a partial Achilles tear. Unlike former teammate Boogie Cousins, he did not suffer the tear on the court, but at home. It was reported that while at home he fell and experienced extra discomfort in his heel. His doctor reported that he will undergo surgery and will likely rehab for the next 11 to 15 months.

Achilles Ache

The Achilles is a tendon (tissue that attaches muscle to bone) connecting the bottom of one’s calf to the back of the heel, as shown in Figure 1. It is famously named after the Greek hero whose only weakness was the back of his heel.

An Achilles tendon attached to the heel and calf (Soleus).
Figure 1: This shows the lower half of a human’s leg, where the Achilles tendon is attached to both the heel and calf (Soleus). Modified from Wikimedia Commons.

According to “The Achilles tendon: fundamental properties and mechanisms governing healing” by Freedman et al, the Achilles tendon is the strongest and largest tendon in the entire body, and can bear up to 3500N, or almost 800lb, before completely rupturing. This is a result of the materials that the Achilles is made of. The tendon is 90% collagen, which forms a structure full of fibers that are bound together by other molecules. The tendon is 2% elastin, which like the name suggests, adds some elastic, or stretchy, properties. The tendon is sometimes characterized as a viscoelastic material, meaning it has both viscous (slow to deform) and elastic properties. However, the Achilles is mostly elastic, allowing it to bear relatively high impacts and loads.

Healing the Heel

The Achilles, much like other tendons and ligaments, has interesting healing characteristics and procedures. There are two common recoveries for a tear in the Achilles: a surgery that stitches the ends of the tears together followed by rehabilitation, or a period of rest followed by rehabilitation. For a full tear, surgery is very common, as the torn tendon ends are not always spatially close enough for natural healing processes to occur. For a partial tear, a doctor in consultation with the patient will decide which of the two options will be best.

Experimental Excitement

While there is much more to study with regards to Achilles tear recovery, there is a lot of exciting research being performed on animal models. One study shows that stretching and compressing the Achilles at certain angles during recovery may lead to better long term health of the Achilles. Another study shows the efficacy of stem cell therapies. A third study shows the usefulness of incorporating a 3D printed structure to integrate the ends of torn Achilles. Essentially, this would connect each end with a scaffold that allows for the reintegration of the tendon. This is very similar to an experimental ACL reconstruction technique called BEAR. A video about BEAR can be seen below.

Although John Wall’s career may be in doubt, the future for effective therapies in treating Achilles related injuries is promising. This is exciting for the future, and hopefully will make for a better patient experience. To read more about the Achilles, click here or here.