Rest periods make all the difference
I sometimes look back at how I trained in my 20s and early 30s and the countless mistakes I made with my training. One of the biggest mistakes was not really understanding how to get the most out of my training by giving the body ample rest between exercises/sets. The amount of time you rest between active (working) sets is really important - rest for too long and it may effect your goal (e.g. fat burning or muscle building), don’t rest enough and your muscles don’t have enough time to recover and therefore your muscle growth will be inhibited and/or you won’t increase your strength.
As I’ve moved onto more calisthenics/bodyweight training, I’ve learnt the importance of rest periods and giving the body time to recover - especially because this type of training has a significant affect on the central nervous system as well as the working muscle groups. As I’ve learnt from the amazingly comprehensive Defying Gravity training manual, sticking to rest periods for strength training is especially important. From between 3-5 minutes rest period between exercises, the chemical within the body responsible for ‘powering’ big movements (Adenosine triphosphate - ATP) will be fully restored.
As a general rule, I recommend the following rest periods:
Endurance / core work e.g. circuits - 30-60 seconds rest between circuits (including boxing training)
Muscle building (‘hypertrophy’) - 90 seconds to 2 mins (to put the muscles in a hypoxic state to force greater muscle growth) for single sets or super-sets (two exercises performed back-to-back)
Strength training (including gymnastic/bodyweight exercises) - 2-3 minutes.