Theres good reason for this: HIIT is a valuable and effective method for improving sports performance and stripping away body fat. In fact, short-term studies show that the training effects of HIIT are equal to traditional endurance training, yet require only a fraction of the time.

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For instance, McMaster University scientists found that when people did just four to six 30-second all-out sprints on an exercise bike, they experienced the same improvements in cardiovascular fitness as those who pedaled at moderate pace for 90 to 120 minutes. During the six-week study, the total amount of actual work for the interval group was only 15 minutes compared to 630 minutes for the endurance group. While it may seem like a no-brainer in regard to what works best over the short-term, theres a dirty little secret in regard to HIIT that rarely gets explained.

HIIT can be HARD, UNCOMFORTABLE, and sometimes NAUSEATING, if youre not prepared for it.

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Many a guy has hit the gym with the best of intentions to follow the latest gut-busting interval workout only to find it nearly impossible to complete. But it doesnt have to be that way. You can get the benefits of HIIT without crushing your bodyand your soulby progressively increasing your intensity over time.

After all, why would you start HIIT with the same routine as someone who has been training this way for a good amount of time? Use this progression to ramp-up your workout as you ramp-up your fitness, for better results (and a more enjoyable experience).

Weeks 1 to 3 Do tempo intervals two times per week. You can run, use an exercise bike, or really, whatever mode of exercise you like. (Dont overcomplicate it.) These are short, 10-second bursts done at a moderate pace, with 50 seconds of slow activity done as the rest. Perform a total of 10 intervals.

Work: 10 seconds at an effort level of 7 out of 10 Rest: 50 seconds of easy exercise Number of intervals: 10

Week 4 Do 15 minutes of continuous activity two times a week. The point of this break in intervals is for both physical and mental restoration. Embrace it.

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Week 5 to 8 Do high resistance intervals two times a week. You can perform this on an exercise bike by dialing up the resistance on the device, or perform sled drags or uphill runs. Youll do just 6 seconds of all-out work, followed by 60 seconds of complete rest. Each time you do the workout, reduce your rest period by 5 seconds.

Work: 6 seconds of maximum effort Rest: 60 seconds in your first workout, down to 30 seconds in your last workout. Number of intervals: 10

Week 9 Do 30 minutes of continuous activity two times a week. Once again, this is a restorative week. You go longer than you did in Week 4 because youre now better conditioned.

Weeks 10 to 12 Do four to six sprint intervals on a track or exercise bike two times a week. Go hard for 30 seconds, and then rest for 4 minutes. Each time you do the workout, reduce your rest period by 30 seconds.

Work: 30 seconds of best effort Rest: 4 minutes in your first workout, down to 90 seconds by last your workout. Number of intervals: 4 to 6 (start with 4 and add 1 per workout)