Slow movements and relatively high weights are one of the keys which make high intensity training very effective if your goal is strength, toning and long term health.
Choose a weight which does not allow you to complete more than 10 extremely slow repetitions with correct form.
Perform the 9 to 10 repetitions in 90 to 100 seconds. Example: 4 seconds up, 2 seconds hold, 4 seconds down.
This slow movement allows you to focus on high muscle tension and correct form on each single repetition.
As soon as you can do 10 repetitions in 100 seconds, it’s time to increase the weight on the next workout.
Variety: Replace one exercise every 4 to 6 weeks.