To make gains in fitness, daily consistent hard work to build training stress (and fatigue) is necessary in order to create the need for the body to adapt. How you adapt to the fatigue will solely depend on how you train, and what systems you targeted. Adapting, the part of training most commonly overlooked, all depends on how well you recover from the training fatigue you have accumulated. Individual responses to training stress may differ, depending on genetics and fitness levels; however, there will always be an individual limit to the level of fatigue that can be handled before you lose the ability to adapt to any amount of training stress.
The General Adaptation Syndrome, a three phase response to physiological stress, was introduced by Canadian biologist Hans Selye in 1936. John Garhammer, Ph.D., a specialist in biomechanics and physiology, later took Hans Seley’s work and applied it to resistance training and exercise conditioning. The work of Selye and Garhammer established the groundwork for learning how the human body reacts to training stress, and more importantly, how it adapts.
Let’s discuss and apply the three phases of the General Adaptation Syndrome (the alarm, resistance and exhaustion phase) to endurance training.
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Shock and Alarm Phase
When the body experiences a new or more intense stress, the first response is the “shock and alarm” phase. This phase, lasting from a few days to several weeks depending on the volume of stress, is usually accompanied with soreness, stiff muscles and a drop in performance. During the initial shock to the system, the stress hormones cortisol, adrenaline, and noradrenaline are released to provide instant energy, which helps you handle the stress at hand. Hard group efforts, races, or hard training days will trigger shock or alarm mechanisms, all of which are a normal part of training as long as they are used in moderation. Experiencing shock and alarm responses too often during a training period will lead to greater decreases in performance, performance levels too low to benefit from, and prolonged muscle recovery. For these reasons alone, training variation is important to allow for proper recovery from hard effort days.
The resistance phase happens after the shock and alarm phase and is when the body adapts to bouts of intense stress by returning to a more normal state. This stage demonstrates the body’s ability to withstand stress. During this stage the body will rely on neurological adaptations mainly to produce power, while the muscle tissue adapts by making various biochemical, structural and mechanical adjustments, eventually leading to increased power and performance. This phase is often referred to as supercompensation. An example of this is when you feel a boost in performance days after a short race or a hard training day. The body will continue to demonstrate its ability to withstand stress for an extended period of time, usually over two or three solid weeks of training. However, if stress persists for too long of a period without proper recovery, the exhaustion phase is reached.
The exhaustion phase is a place you never want to be. The goal is to stop training after two to three weeks and spend at least a week recovering with extra rest days and fewer training hours. If training continues and you reach exhaustion, you will experience some of the same symptoms as the alarm phase (soreness, fatigue, and drop in performance), plus lose the ability to adapt to further amounts of increased training stress. This is where athletes reach a plateau in training. Very motivated athletes can easily push into the exhaustion phase, where it is common to blame the decline in performance on a lack of hard training. This is where some athletes will continue to dig a bigger hole with more training and eventually suffer from an over trained state, experiencing emotional and sleep disturbances along with further declines in performance. Recovering from a severe case of over training syndrome can take a very long time, from many months to many years.
Learning how and when to recover is the most important aspect of training, and it starts with learning how your body handles training stress and fatigue. Full muscle recovery leads to increased performance, prevents exhaustion and over training. The more often you can perform on a higher level, the stronger you will become.
Mike Schultz, CSCS
For more info on gauging and dealing with fatigue, see this article – Follow Your Heart: Using HR to Gauge Fatigue
1- Selye, Hans. “Stress and the general adaptation syndrome.” British Medical Journal. 1950, pp. 1383–1392