Interference of strength development by simultaneously training for strength and endurance.
Level 3 - non-randomized controlled study
Controlled exercise intervention trial without explicit mention of randomization in the abstract.
PubMed 7193134 · doi:10.1007/BF00421333
What was done
Participants were assigned to one of three exercise regimens for 10 weeks: a strength-only group (S, 30–40 min/day, 5 days/week), an endurance-only group (E, 40 min/day, 6 days/week), or a combined group (S and E) performing both daily training protocols. Adaptations in maximal oxygen uptake (VO2max) during bicycle and treadmill testing and leg-strength gains were compared across groups.
What was found
After 10 weeks, VO2max increased by approximately 25% on bicycle testing and 20% on treadmill testing in both the E group and the S and E group, whereas the S group experienced no increase. The S group showed a consistent rate of leg-strength improvement throughout the 10 weeks, while the E group showed no appreciable strength gains. The combined S and E group matched the strength gains of the S group for the first 7 weeks, but strength progress subsequently leveled off and declined during weeks 9 and 10.
Why it matters
This foundational study established the interference effect, demonstrating that concurrent endurance and strength training attenuates long-term strength adaptations while leaving aerobic fitness gains intact.
Limits
The abstract does not report the sample size, participant demographics (such as sex, age, or baseline training status), or whether group allocation was randomized. Specific absolute or relative strength values and statistical variance metrics are omitted. The high training volume in the combined group (daily strength plus endurance) introduces potential confounding from overtraining or fatigue rather than pure physiological pathway interference.
Cited by
- supports Robert Hickson's classic research suggested an interference effect between concurrent endurance and resistance training on strength gains.