Is Explosive Strength More Susceptible to the Interference Effect than Strength and Hypertrophy?

Is Explosive Strength More Susceptible to the Interference Effect than Strength and Hypertrophy?

The interference effect describes how combining endurance and strength training can reduce the rate of improvement in one or both qualities. While this effect can influence many aspects of performance, research suggests that explosive strength may be more susceptible than maximal strength or hypertrophy.

Explosive strength refers to the ability to generate force rapidly. It relies heavily on high-velocity muscle contractions and the recruitment of Type IIx fibres, which are the fastest and most powerful fibres in the body (Schiaffino & Reggiani, 2011). These fibres are large, rely on glycolytic metabolism, and fatigue quickly. They are also more sensitive to changes in training stimulus and recovery status.

Meta-analyses by Petre et al. (2021) and Schumann et al. (2022) have found that concurrent training tends to have a minimal effect on maximal strength and hypertrophy, especially in trained individuals. However, measures of explosive performance, such as vertical jump height, sprint speed, or high-velocity force output, are more likely to improve less when endurance work is added to strength training.

One reason is fibre type conversion. Endurance training encourages a shift from Type IIx to the more oxidative Type IIa fibres (Andersen & Aagaard, 2000). This shift reduces the proportion of the most explosive fibres, even if maximal strength remains relatively unchanged. Regular strength training without high-velocity work can also lead to this shift, but concurrent training seems to accelerate it.

Another factor is fatigue management. Explosive strength is highly sensitive to fatigue, whether from central sources (reduced nervous system drive) or peripheral sources (accumulation of hydrogen ions and phosphate) (Gandevia, 2001). Even mild fatigue can impair high-velocity force output. Endurance sessions placed too close to explosive training can deplete glycogen, increase metabolic by-products, and reduce recruitment of Type IIx fibres.

A third consideration is recovery time. Maximal strength and hypertrophy can tolerate more residual fatigue because they involve slower contractions and do not require full recruitment of the fastest fibres. Explosive strength demands freshness to access and train Type IIx fibres effectively. In practical terms, an athlete can perform a heavy squat with some fatigue and still hit a high load, but their sprint or jump performance will be more noticeably affected.

This does not mean explosive strength cannot improve in a concurrent programme. It means it requires more careful planning. Athletes may need to schedule explosive work on days with full recovery before and after, keep endurance volumes appropriate for their sport, and ensure glycogen replenishment. Endurance modalities that produce less muscle damage, such as cycling instead of running, can also help reduce interference.

In summary, explosive strength appears more susceptible to the interference effect than maximal strength or hypertrophy. This is due to fibre type shifts, greater sensitivity to fatigue, and the need for optimal recovery to train high-velocity movements effectively.

Are you looking to structure your strength and endurance training but not sure how? Check out our training plans. 

Dr Phil Price

Head of Sport Science at Omnia Performance 

References

• Andersen, J. L., & Aagaard, P. (2000). Myosin heavy chain IIX overshoot in human skeletal muscle. Muscle & Nerve, 23(7), 1095–1104.
• Gandevia, S. C. (2001). Spinal and supraspinal factors in human muscle fatigue. Physiological Reviews, 81(4), 1725–1789.
• Petré, H., Hemmingsson, E., Rosdahl, H., & Psilander, N. (2021). Development of maximal dynamic strength during concurrent resistance and endurance training in untrained, moderately trained, and trained individuals: A systematic review and meta-analysis. Sports Medicine (Auckland, N.Z.), 51(5), 991–1010.

• Schiaffino, S., & Reggiani, C. (2011). Fiber types in mammalian skeletal muscles. Physiological Reviews, 91(4), 1447–1531.
• Schumann, M., Feuerbacher, J. F., Sünkeler, M., Freitag, N., Rønnestad, B. R., Doma, K., & Lundberg, T. R. (2021). Compatibility of concurrent aerobic and strength training for skeletal muscle size and function: An updated systematic review and meta-analysis. Sports Medicine (Auckland, N.Z.), 52(3), 601-612.