To interval train, simply push yourself to your maximum effort for several minutes several times in your routine, with short periods of rest in between sets. (functionalhealthnews.com)
You need periods of rest in order to keep your intensity high and progress moving forward. (coachcalorie.com)
I know for me, it has been a wrestling match (with periods of rest between rounds) that has been going on for several years. (redeeminggod.com)