Table 1

Exercise training principles

PrincipleCriteria for this reviewExample
Specificity: Training adaptations are specific to the system or muscles trained with exercise.Appropriate population targeted and intervention given based on primary outcomeAerobic 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 must be increased.Stated exercise programme was progressive and outlined training progressionA walking intervention 2×/week at 60% of maximum heart rate for 30 min, adds 5 min/week over 6 weeks
Overload: For an intervention to improve fitness, it must be greater than what the individual is already doing.Rationale provided that programme was of sufficient intensity/exercise prescribed relative to baseline fitness.An individual currently cycles 30 min 2×/week; the exercise intervention must be of greater volume to see a significant improvement in fitness.
Initialvalues: 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 levelsThose with lowest levels of fitness have greatest room for improvement. A sample with high fatigue levels will be more likely to see a significant change than a sample with low baseline 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‘Use it or lose it’. Strength gains achieved over 1 year of resistance exercise may completely reverse within a number of months of inactivity.
Diminishingreturns: The expected degree of improvement in fitness decreases as individuals become fit, thereby increasing the effort required for further improvements.Performed follow-up assessment of primary outcomes on participants who continued to exercise after conclusion of intervention.Non-exercisers who begin an exercise programme are likely to experience large initial gains, but the magnitude of change will decrease over time. This is also known as the ‘ceiling effect’.