8. Add Resistance
Get ready for some pretty heavy stuff: A recent study showed that exercisers who lifted a heavy weight for just eight reps burned double the calories of those lifting lighter weights for 15 reps.
Try implementing this rule of thumb: Keep adding weight (in small 2- to 5-pound increments) to an exercise until achieving three sets of 10 reps becomes very challenging (as in almost impossible to squeeze out the final rep!). Practice with that weight until 10 reps becomes too doable and then add a few more pounds of resistance.
9. Complete the Circuit
Quickly moving from one exercise right into the next is a great way to create a time-efficient, cardio-focused workout. When setting up a circuit, just be sure to slot exercises that target different muscle groups back-to-back to avoid burnout. For example, perform squats before a chest press, and then a deadlift followed by a plank. This gives each muscle group enough time to recover while the next body part is targeted.
More: 30-Minute Full-Body Circuit Routine
10. Aim for Failure
Failure occurs when a muscle is so spent it can't complete one more repetition of an exercise (while maintaining proper form).
Good news is, the struggle is well worth the effort. Research suggests training to failure can increase strength and improve the body's ability to build lean muscle. One way to reach failure is through super-slow movements using relatively light resistance.
Slowing down the tempo of each rep causes greater muscle contractions and has been shown to increase strength gains. Think about taking 10 seconds to complete a single push-up for 10 seconds. (Beginners: Be sure to try this one with a trainer first to ensure proper safety!)