23/10/2022
Interference Effect (IE)
The first study to identify the IE was back in 1980. Since then, it has been examined frequently with particular interest in strength adaptations, hypertrophy and power/explosive adaptations.
What is the IE?
Research shows that when performing cardio training during periods of strength training, cardio training reduces the strength & size adaptations (compared with strength training alone - without cardio happening).
The type of endurance activity can influence the magnitude of the IE with running causing the greatest negative effect on strength development.
The greater the volume & intensity of the cardio training the greater the IE.
(Interestingly, strength training can enhance endurance performance when strength & endurance are are performed during the same periods).
What causes the IE?
This is complex & remains unclear.
Current research position on IE?
The most recent meta-analysis examining the IE confirms that it is measurable & present.
A notable & important finding is that power & explosive strength are more significantly negatively impacted.
Does it matter?
The majority of the strength training population need not be concerned about including some cardio training, on the contrary, this should be regarded as a healthy lifestyle mix.
Performance athletes on the other hand, in particular those who have significant goals related to explosive strength &/or power e.g. sprinting, jumping, throwing - must consider the negative impact that endurance training will likely with progress.
Team sport athletes must be mindful that intensive conditioning sessions have the potential to reduce explosiveness & agility.
If the athlete/player goal is maximum speed, development, maximum power output & improved explosive qualities, then consider the IE & limit endurance training as much as feasible.
Competitive Powerlifters - although the IE appears to be relatively small (dose dependant), it is still negative.
Powerlifters wishing to include cardio for physiological (& mental) benefits - consider completing cardio sessions after your strength session not before, don’t complete large volumes of cardio & reduce it when you want to peak strength, consider separating endurance & weight training sessions by 24 hours.
Competitive Bodybuilding - no logical reason to include aerobic exercise - nutrition should be the priority if reductions in body-fat percentages are required.
J.
