This is an excerpt from Practical Guide to Exercise Physiology-2nd Edition by Robert Murray & W. Larry Kenney.
Optimal adaptations in functional proteins within cells occur in response to periodically overreaching during training, pushing the body so that it naturally adapts to increasing levels of exercise stress. A central challenge in designing any training program is to ensure that functional overreaching does not progress into nonfunctional overreaching or overtraining. One way to accomplish that goal is to follow the principles of progressive overload and variation (periodization), as illustrated in figure 5.4.
The example in figure 5.4 shows how an eight-month training program with a specific goal (that could be a weight-loss goal, a strength-related goal, a performance goal, can be broken down into training segments, or cycles. In this example, two four-month macrocycles allow for subgoals to be established so that progress toward the ultimate goal can be assessed along the way. That same approach also applies to the two-month mesocycles and the two-week microcycles. Dividing a training program into separate parts allows each part to be designed to accomplish specific fitness goals that progressively build toward the ultimate goal. If sufficient progress is not made within a microcycle, then subsequent training can be altered to ensure that future subgoals can be met. It should be noted that training responses rarely unfold as nicely as depicted in figure 5.4. The true value of periodization may be as a conceptual approach to structuring long-term training programs to include the important aspects of the five principles of training. For example, traditional training programs for individual sports such as running, swimming, cycling, and triathlon stress the development of an aerobic base in the early season, with emphasis on lower-intensity, longer-duration efforts. Midseason training focuses on increased intensity efforts and late-season workouts leading up to a final taper typically featuring very high-intensity work of shorter durations. Training for team sports such as football, soccer, ice hockey, volleyball, and basketball often requires heavy training early in the competitive year, supported by maintenance training once the hectic competitive season begins.
According to some research, periodized block training will provide superior results compared to traditional approaches. Instead of combining all aspects of training throughout each week, block training stresses a changing weekly or biweekly focus (microcycles) on the development of strength, endurance, power, skills, or whatever elements the coach deems important.
Notice in figure 5.4 that every increase in training capacity (the central black line) is followed by a period in which training workload plateaus (or in some cases may even decrease). Periodically lowering the training workload for a few days or even longer allows time for adaptations in functional proteins while reducing the risk of nonfunctional overreaching or overtraining. Keep in mind that figure 5.4 is simply one example of how the principles of progressive overload and variation (periodization) can be integrated into a training program that incorporates macro-, meso-, and microcycles.
Other variations in training program design include hard training for a certain number of days, followed by the same number of days of rest or reduced workload. Some coaches follow the 75% rule: 75% of training completed at an intensity less than 75% of maximal heart rate (HRmax), 15% of training at moderate intensity (e.g., 75%-85% HRmax), and 10% at a high intensity (e.g., greater than 85% HRmax). There are countless ways to structure effective training programs. The challenge is to identify training programs that best match the needs, interests, goals, and capacities of individual athletes and clients.
Before important competitions, the training load should be gradually reduced to help maximize the various adaptations to training. This reduction in training load is commonly referred to as tapering. Research with swimmers, runners, and cyclists indicates that the optimal tapering strategy is accomplished over the two weeks before an important competition by decreasing the training volume by 40% to 60% without changing training intensity or frequency.