Table 1 Exercise training principles

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 programme was progressive and outlined training progression

Increase duration of walking program by 5% every two 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 programme 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