Aquatic or underwater treadmill exercise is gaining popularity as a means of exercise training in persons with osteoarthritis who cannot exercise on a land treadmill. Water jets opposite to the direction of walking can be used to achieve high ratings of perceived exertion in aquatic treadmill. Water currents in the direction of walking can also support higher speeds if needed, for a morale boost, in those with lower exercise capacity. The advantage of underwater treadmill is that there is no joint impact due to the body weight as occurs with land treadmill.
Both motorised and non motorised versions of aquatic treadmills are available as in case of land treadmills. The non motorised versions are obviously cheaper because there is no need for costly underwater durable motors. Aquatic treadmills can be portable or custom made and fixed in a pool.
Aquatic treadmill is very useful for senior citizens to avoid the risk of falls and musculoskeletal stress of land treadmill exercise. Regular exercise can improve lean body mass and overall physical fitness in the elderly. It is also useful for obese individuals and those with issues of mobility. Underwater treadmill is useful in those recovering from stroke as they often have poor balance or cannot support their weight. Unlike in land treadmill, aquatic treadmill can have advantages due to characteristics of water like temperature, viscosity and hydrostatic pressure.
Cardiovascular changes occurring during immersions have also to be taken into account. There is redistribution of blood volume from the lower limbs to the thoracic cavity. But the increases in blood pressure, heart rate and rate pressure product are lower with underwater treadmill walking as compared to walking on a land treadmill .
Underwater treadmill gait training has been shown to be more effective in improving gait and respiratory function in severe stroke patients . Twenty two severe hemiplegic stroke patients were randomized to underwater treadmill or overground gait training in this study.
A pilot study evaluated underwater treadmill gait training with water jet resistance in 22 chronic stroke patients . Underwater treadmill gait training with water jet resistance was found to be effective in improving static and dynamic balance as well as gait abilities in chronic stroke patients.
Another study evaluated aquatic treadmill walking in those with traumatic brain injury . Walking in water at three depths (waist, chest and neck levels) were evaluated. Depth adjustment was made by a movable pool floor. They found that walking in neck depth water may not be ideal for gait training as it appeared to limit hip flexion and ankle dorsiflexion. They recommended waist to chest depth water for aquatic gait rehabilitation.
Yoo J et al. Cardiovascular Response During Submaximal Underwater Treadmill Exercise in Stroke Patients. Ann Rehabil Med. 2014; 38: 628–636.
Narasaki-Jara M, Wagatsuma M, Holt JL, Acuña SM, Vrongistinos K, Jung T. Aquatic treadmill walking at three depths of water in people with traumatic brain injury. Physiother Res Int. 2020 Apr;25(2):e1817.