SHAPE
By Daryl Conant, M.Ed
Mix It Up with Cross-Training
s the public’s knowledge about the benefits of exercise con- tinues to grow, so does the demand for diversified program- ming. Not only must fitness programs appeal to a wider group of people than ever, but they must also be varied enough to hold the interest of exercisers and to promote overall fitness without injury. The best way for health clubs to meet this need is through the
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development of cross-training programs. From a clinical standpoint, cross-training enables individuals to place significant demands on the heart and circulatory system, since it typically involves aerobic- type activities. Cross training produces increased cardiac output, blood volume and a greater number of red blood cells, which ulti- mately enhances the body’s ability to transport oxygenated blood to the exercising muscles.
Physiologic Changes from Cross-Training
In response to engaging in aerobic-type cross-training on a regular basis, several significant changes take place within the muscle cells.
• The number and size of mitochondria (organelles in the muscle cells that produce ATP for energy) increase. • The amount of glycogen (carbohydrates) stored in the muscle increases. • Concentration of important enzymes (within the mitochondria that are involved in the production of ATP) increases. • The amount of triglycerides (fat) stored in the muscle increases. • The ability to oxidize fat from primarily muscle-fat stores, but also from adipose tissue stores, increases.
This enhanced ability to use stored fat results in less glycogen depletion, less lactic acid accumulation and, concomitantly, less muscular fatigue and better endurance. These changes, called peripheral adaptations, help the muscles
contract repeatedly and more efficiently during exercise. Periph- eral adaptations are activity-specific (i.e., they differ from activity to activity). For example, trained distance runners cannot transfer their high level of endurance for running to swimming because the peripheral muscular adaptations required for optimal performance are different for swimming.
20 Essential Living Maine ~ February 2015 Digital Edition
The combined effect of peripheral and central adaptations determines the quality of performance. Improving one without the other, however, produces limited improvements in sport-specific performance. Accordingly, while cross-training may offer certain advantages for the typical fitness enthusiast, it may also have a few limitations for competitive athletes. As a result, individuals who know exactly what they want from their exercise efforts are better able to decide whether to engage in cross-training.
The Benefits of Cross-Training Incorporating several different forms of exercise in a training
program can be an excellent way to develop various components of fitness. The following are among the numerous benefits of cross- training that have been documented.
• Reduced risk of injury. By spreading the cumulative level of orthopedic stress over additional muscles and joints, individuals are able to exercise more frequently and for longer durations without excessively overloading particularly vulnerable areas of the body (e.g., knees, hips, back, shoulders, elbows, and feet). For example, individuals who are particularly prone to lower-leg problems from running long distances should consider incorporating low-impact activities such as arc trainers, cycling and swimming into their regi- men.
• Enhanced weight loss. Individuals who want to lose weight
and body fat should engage in an exercise program that enables them to safely burn a significant number of calories. Research has shown that such a goal, in most instances, is best accomplished when individuals exercise for relatively long durations (i.e., more than 30 minutes) at a moderate level of intensity (i.e., 60 to 80% of maximal heart rate). Overweight individuals can safely enhance weight and fat loss by combining two or more physical activities in a cross-training regimen. For example, such a person can exercise on an arc trainer for 20 to 30 minutes and then cycle for an addi- tional 20 to 30 minutes. • Improved total fitness. Cross-training can include activities
that develop muscular fitness, as well as aerobic conditioning. While an individual’s muscular fitness gain will typically be less than if he/she participated only in strength training, the added benefits of improving muscular strength and endurance can pay
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