Concurrent Training: A Meta Analysis Examining Interference of Aerobic and Resistance Exercise
Wilson, Jacob M Ph.D, CSCS*D; Marin, Pedro J Ph.D.; Rhea, Matthew R Ph.D.; Wilson, Stephanie MC M.S, R.D, L.D.N; Loenneke, Jeremy P M.S; Anderson, Jody C Ph.D., ATC, PT, SCS
The primary objective of this investigation was to identify which components of endurance training (e.g. modality, duration, frequency) are detrimental to resistance training outcomes. Methods: A meta-analysis of 21 studies was performed with a total of 422 effect sizes. Criteria for study inclusion were (a) compare strength training alone to strength plus endurance training (concurrent), or to compare combinations of concurrent training, (b) the outcome measures include at least one measure of strength, power, or hypertrophy and (c) the data necessary to calculate effect sizes must be included or available. Results: The mean ES for hypertrophy for strength training was 1.23, for endurance training was 0.27, and for concurrent training was 0.85, with strength and concurrent training being significantly greater than endurance training only. The mean ES for strength development for strength training was 1.76, for endurance training was 0.78, and for concurrent training 1.44. Strength and concurrent training were significantly greater than endurance. The mean ES for power development for strength training only was 0.91, for endurance training was 0.11, and for concurrent training 0.55. Significant differences were found between all three groups. For moderator variables, resistance training concurrently with running, but not cycling, resulted in significant decrements in both hypertrophy and strength. Correlational analysis identified significant negative relationships between frequency (-.26 to -.35) and duration (-.29 to -.75) of endurance training for hypertrophy, strength, and power. Significant relationships (P< 0.05) between ES for decreased body fat and % maximal heart rate (r: -0.60) were also found. Our results indicate that interference effects of endurance training are a factor of the modality, frequency, and duration of the endurance training selected.