Table 1.
Principles of exercise training
| Principle | Criteria for this review | Example |
|---|---|---|
| Specificity: Training adaptations are specific to the organ system or muscles trained with exercise | Appropriate population targeted and modality selected based on primary outcome | Aerobic exercise such as brisk walking is more appropriate for an intervention aimed at increasing cardiovascular fitness than strength training |
| Progression: Over time, the body adapts to exercise. For continued improvement, the volume or intensity of training must be increased | Stated exercise program was progressive and outlined training progression | Increase duration of walking program by 5% every 2 weeks depending on exercise tolerance |
| Overload: For an intervention to improve fitness, the training volume must exceed current habitual physical activity and/or training levels | Rationale provided that program was of sufficient intensity/exercise prescribed relative to baseline capacity | Prescribing intensity in a resistance training program based on % of measured and/or estimated 1-repetition maximum |
| Initial values: Improvements in the outcome of interest will be greatest in those with lower initial values | Selected population with low level of primary outcome measure and/or baseline physical activity levels | Selecting a sample with high baseline fatigue levels to participate in an aerobic training program to increase cardiovascular fitness and reduce fatigue |
| Reversibility: Once a training stimulus is removed, fitness levels will eventually return to baseline | Performed follow-up assessment on participants who decreased or stopped exercise training after conclusion of intervention | Participants who maintained training after a supervised exercise program preserved strength whereas those who stopped exercising returned to baseline |
| Diminishing returns: The expected degree of improvement in fitness decreases as individuals become more fit, thereby increasing the effort required for further improvements. Also known as the ‘ceiling effect’ | Performed follow-up assessment of primary outcomes on participants who continued to exercise after conclusion of intervention | Gains in muscle strength are greatest in the first half of a training program unless the training stimulus continually increases |