Rated as the No.1 fitness trend for 2014 by American College of Sports Medicine fitness professionals, high-intensity interval training is increasingly being used to make short workouts more intense. Although you may be getting results from HIIT training now, that doesn’t necessarily mean performance increases are being made in the long run. Follow these three HIIT tips to take your workouts to the next level, and make consistent body composition and strength improvements.

Timing matters

A typical HIIT session should last anywhere between 4 minutes (like Tabata) and 15 minutes. Overuse injuries can arise if workouts are too long; cap HIIT workouts at 30 minutes.

But instead of putting together a 30-minute, non-stop workout, break up your program into shorter all-out intervals with brief recovery periods. For example, three workouts of 5-7 minutes each with a short recovery between each one will allow for a higher level of intensity, and keep you from getting bored doing the same movements over and over again.

Make HIIT more intense

HIIT recovery periods can be active (such as a plank) or at full rest. Either way, a basic work-to-rest ratio is one minute work to two minutes rest. A good rule of thumb: you should not be able to talk and work out simultaneously during a well-programmed HIIT workout. Here's an example of a basic HIIT rowing workout.

Basic HIIT rowing workout
4 rounds
250 meters rowing
Work to rest ratio: 1:2
Total time: 12 min.

To avoid hitting a fitness plateau, and to continue improving your conditioning, add an extra work interval and/or reduce the duration of rest periods in subsequent workouts. Here’s a progression of the program above:

More intense HIIT rowing workout
8 rounds
250 meters rowing
Work to rest: 1:1
(Resting for approximately 1 minute) 
Total time: 16 min.

Integrate strength training and HIIT

Building and maintaining muscle is a critical component of conditioning. Not only is it safe to incorporate HIIT and strength training, it's an efficient way to maximize lean body mass and maintain strength. To do this, try a strength-training workout that consists of 1-2 exercises and 5-6 sets of each. Here's an example of a strength component of a workout routine:

Strength workout
Back squats (working up to 5RM)
Sets: 5
Reps: 5
Superset with
Pullups
Sets: 5
Reps: 10

Here’s an example of how to tie all of this together, and structure an entire strength and conditioning session:

Full-body metabolic workout

Mobility and dynamic stretching
Duration: 10 minutes

Strength training
Duration: 15 minutes

HIIT
Duration: 15 minutes

Cool down (stretching)
Duration: 5-10 minutes