1) Exercise 2) Exercising 3) Form of strength training 4) Isometric exercise 5) Muscle strengthening method 6) Physical exercise 7) Physical exertion 8) Strength-training exercises 9) Workout 
exercise or a system of exercises in which opposing muscles are so contracted that there is little shortening but great increase in tone of muscle fibers involved.
[n] - muscle-building exercises involving muscular contractions against resistance without movement (the length of the muscle does not change)
isometrics A form of exercise in which the muscles are pushed against something fixed or against other muscles to strengthen them.
isometric exercise noun muscle-building exercises (or a system of musclebuilding exercises) involving muscular contractions against resistance without movement (the muscles contracts but the length of the muscle does not change)