The heat is on in the world of exercise mimetics. Exercise what? Exercise mimetics, the odd but essential field focused on how to mimic the physiological effects of physical activity without the physical activity. You might say, an armchair science. Odd, because it involves highly sophisticated and costly research attempting to uncover what happens when you break a sweat, something neither sophisticated nor costly. Essential, because insufficient physical activity is now a leading cause of illness.
This is good news for those folks who when they think about exercising lay down until the thought goes away. Recent research suggests that a daily dip in a hot bath may provide many of the health benefits seen with exercise. Just getting hot helps.
Why would it be possible to fool the body so easily? And why is physical activity good for you in the first place?
The answer to these questions provides a blueprint for designing a healthy lifestyle. Two key concepts underlie the explanation to both: homeostasis and stress.
Let's start with homeostasis, the biology of staying the same.
Border control is not unique to nation states. The first assignment of every cell is to secure its perimeter. Without this separation of inner and outer spaces, there would be no life, as we know it. The skins of cells, organs and entire animals actively maintain the essential conditions of a stable inner sanctum. This dynamic equilibrium of a steady state resisting constant external forces of change, like a ship in shifting seas, is homeostasis.
We can exist only within a narrowly defined internal environment. For instance, we may be able to live indefinitely in conditions that range between about 4 and 35 degrees C (40 and 95 degrees F). However if our core body temperature drops or increases by 5 degrees C, death is likely. The maintenance of body temperature, blood oxygen levels, fluid and electrolyte balance, and metabolic rate are examples of homeostasis at work.
While such stability is necessary for survival, it is not enough for health. Our body has a love-hate relationship with change. It conservatively guards a status quo but thrives on challenges to this balanced baseline. Another term for such challenges is stress. And contrary to popular belief, we have too little stress in our lives. For a review of the health benefits of stress see The Next Prescription: Primal Stress and No Strain No Gain: How stress can make you stronger
Our genome is the crowning achievement of adaptation to a life that no longer exists. In surviving as hunter-gatherers, populating the earth as agriculturalists and building the modern world as industrialists, we have created an environment that is alien to our biology. The absence of formative ancient stressors has disrupted the remarkably resilient biological regulation that allowed us to survive.
A hot bath warms our muscles, as does exercise. This increase in temperature triggers what's called the heat shock response, a cellular stress response. Heat shock proteins share pathways associated with the body's reaction to exercise. They have been shown to improve insulin sensitivity (something that is lost in diabetes, obesity and metabolic syndrome), reduce inflammation and decrease both body fat and weight.
Just 3 weeks of daily hot tub immersion caused a decrease in blood sugar levels and weight in type 2 diabetics.
Is a hot bath a replacement for exercise?
Afraid not. You won't burn nearly as many calories, build muscle or strengthen bone. But a hot bath will improve your health.
So go ahead, get in hot water.