IF YOU’RE DOING RESISTANCE TRAINING AND CARDIO IN THE SAME SESSION YOU’RE DOING IT WRONG!
It’s called the Interference Effect. It simply means you are confusing your body by adding endurance work directly after a lifting session. What is your priority- endurance or size/strength?
Researchers had two groups of subjects perform the same lower body power exercises over a six week period. One group did only the lower body exercise while the other group did and additional 30 minutes of low-intensity running at a moderate pace(60-70% of max heart rate) after the lower body power exercise.
The researchers then measured jump performance, leg press force, speed (rate of force), strength via a 1rep max and muscle fiber changes using needle biopsy.
The group that added the 30 minutes of low intensity running could not jump as high and their muscle fibers were smaller(less muscle growth).
There’s nothing inherently wrong with doing both resistance training and endurance training. Timing seems to be the key. Doing endurance training can help your strength/hypertrophy training by enabling you do more work during your resistance program. But doing them in the same session can be detrimental.
If your resistance training program is 3 or 4 days a week do your endurance training on the off days (keeping the intensity moderate). Another alternative is to do your endurance training in the AM and your resistance training in the PM.