Optimal human function is heavily dependent on obeying the natural rhythms of activity and rest built into all of us. This is most obviously demonstrated through our activity during the day followed by our rest at night. But this principle can also be observed through our physiology: The heart and blood vessels have phases dedicated to contraction followed by relaxation, reciprocal inhibition describes the process of muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint.
The Basic Rest Activity Cycle (BRAC) illustrates a cycle of activity and rest operating from a ratio of roughly 90:20. After about an hour of activity we begin to feel tired, hungry, thirsty, need to go to the bathroom, yawn, lose concentration, feel bored and begin to make mistakes. At this point we can either listen to our body and rest, or choose to keep going by mobilising our energy with willpower, caffeine, sugar or exercise. If we override our need for rest, adrenaline levels and mental activity will increase, but if we continue to do this performance will gradually decline. This negative cycle continues as sustained high levels of adrenaline will mean that, though very tired we cannot relax and unwind, even when work stops. Sleep disturbances may also increase. The regular rest breaks which make up the cycle are important for digestion, sustaining immunity and wound healing, maintaining optimal mental functions such as the laying down of long-term memory, making sense of our external world and for slow creative thinking.
Circadian Rhythms describe our typical patterns of daily energy levels. Some people tend to be better in the morning and others are more likely to have higher energy levels in the evening. Identifying where your high and low points are in the day and listening to that can greatly improve you overall function and ability. These rhythms depict physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in our environment. Light is the main cue influencing circadian rhythms, turning on or turning off genes that control an organism’s internal clocks. Circadian rhythms can influence sleep-wake cycles, hormone release, body temperature and other important bodily functions. They have been linked to various sleep disorders, such as insomnia. Abnormal circadian rhythms have also been associated with obesity, diabetes, depression, bipolar disorder and seasonal affective disorder.
THE HUMAN FUNCTION CURVE
A lot of us were taught that in order to do better we must try harder. This advice does have some validity as we function well with lots of energy, creative thought, prompt reactions, steady pace and flexibility. When work stops we enjoy rest and relaxation. However at our optimal capacity for effort, working harder will no longer bring improved performance. The ‘intended performance’ is an illusion fuelled by increased adrenaline levels. If external or internal pressures do not change and we keep trying harder, we move into the downward slope leading fatigue, exhaustion and illness. Despite increased effort, performance declines and it becomes harder to rest when work stops. On the ‘exhaustion’ slope performance will only improve through working less and taking sufficient time to rest and recover. For a lot of people this is counterintuitive and contrary to what they were taught. Initially the ‘exhaustion’ slope is gradual but toward the lower end it becomes very steep. The shift into breakdown of health may occur suddenly and without warning. The point at which we move from the upslope to the downslope varies with stamina and resilience. These will be improved by good self-care including a clean and nutritious diet, regular exercise and adequate rest and relaxation.