Hot Water Immersion
Hydrotherapy is widely used for the treatment and rehabilitation of patients, but it can also be applied to prevent diseases in healthy people. Water offers various advantages, including being abundant; not physiologically irritating; and having an excellent solvency, excellent viscosity, high heat capacity, and high heat conductivity.
The health effects of hydrotherapy generally appear as thermal, mechanical, and chemical effects, either alone or as mixed effects. Heat therapy is typically explained by vasodilation and blood flow facilitation effects. Mechanical effects can be explained by the properties of water, such as buoyancy, hydrostatic pressure, and resistance, where the effect primarily appears when hydrotherapy is provided via immersion therapy. Buoyancy represents the force that opposes gravity, and when the body is partially or fully immersed, pain reduction and improvement in exercise ability occur due to the reduction of stress or application of weight to specific body parts. Hydrostatic pressure promotes blood flow by varying the pressure exerted on the body according to the immersion depth, which results in increased blood flow to major organs (the heart, brain, and lungs) or the promotion of diuretic action.
Heat increases blood plasma volume, which allows your heart to work more efficiently and get more blood, and with it, more oxygen and fiber-repairing nutrients, to the working muscles. Heat also kick-starts the production of heat shock proteins that ultimately can allow for increased blood flow through your capillaries and help remove lactate and acid buildup caused by high-intensity exercise. This can lead to a more rapid recovery. Other research shows that hot-water immersion can relax muscles and soften the collagen in our ligaments, which can help provide pain relief. Soaking in hot water can also help relieve the aches and pains that come from arthritis or general muscle stiffness. The buoyancy of water reduces the impact of gravity on skeletal and muscle tissue, alleviating tension in the body. Warm water also loosens muscles before a workout, or soothes them afterward.
Soaking in warm water causes our body temperature to increase and blood vessels to dilate. This improves circulation, pumping more nutrients and oxygen throughout our bodies while displacing toxins in areas of weaker flow. As the body regulates its internal temperature, our pores release moisture into the water, that carries away internal chemical waste. In this way, soaking in hot water helps reduce toxins and brings benefits to our entire body. The physiological changes induced by warm water immersion, such as vasodilation, increased blood flow, reduction of arterial stiffness, vascular endothelial function, oxygenation, and decreased sleep-related stress, may result in improvements in the cardiovascular function. These physiological changes due to water immersion are similar to the cardiovascular effects of physical activity.
According to research, continued friction generated by the warm water contacting the skin, improved the blood flow throughout the body. As a result, the heart rate decreased to minimize the heart burden due to the increased direct brachial artery blood flow to the cardiac vessels and the blood volume returning to the heart.
Hot water Immersion therapy is extensively used by Dr Biswaroop Roy Chowdhury to treat dialysis patients and kidney failure patients. According to his protocol, when the patient is made to sit in the bath tub with water level upto the neck, there is a 2% increased pressure difference below the neck. This pressure difference results in negative pressure breathing. As a result of this breathing, a 20% increase in the stroke volume of the heart is observed. The heart pumps an increased volume of blood by 20%. This increased blood pumping leads to redistribution of blood from the lower portion of the body to the upper torso, waist upwards. The movement of the blood upwards reduces load on the kidneys and results in certain favourable chemical changes. As a result of HWI, excess sodium and potassium are excreted through the skin. Urine output increases three times and swelling is reduced. Hundreds of kidney patients have benefitted by following his protocol.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6479732/
https://biswaroop.com/endoftransplant/