High Intensity Interval Training (HIIT)
There has been alot of buzz lately in the fitness industry surrounding High Intensity Interval Training (HIIT). This type of cardio training is designed to improve your overall performance as well as burn fat by completing short, very intense workouts. 
High Intensity Interval Training can be applied to most cardiovascular exercise such as; running, cycling, rowing, and skipping. HIIT workouts can last anywhere from 15–30 minutes and include a 2:1 ratio in terms of time. An example of a high intensity interval workout incorporating running could be 1 minute of jogging and 30 seconds of sprinting.
There are however, some precautions when training with this method and perhaps the most important is that this type of training is not for everyone. Since it is extremely high in intensity, beginners and those new to fitness may find that they physically cannot work out at this level and injuries can be at risk. Make sure you have a strong cardio base before beginning any HIIT workout and if you are not ready, try challenging yourself by increasing the difficulty for a few minutes during your workout and begin building towards a HIIT session.
Another concern is proper nutrition and hydration. Make sure you are getting adequate protein and carbs at least an hour before and after your workout. An excellent article, Electrolytes and Proper Hydration for Exercise shows that electrolyte repletion in the form of a sports re-hydration drink with minerals not only promotes post-exercise recovery, but a drink that includes ingredients such as citric acid and malic acid are also necessary for energy production. Further, intake of carbohydrates with a high glycemic index within two hours post exercise is fundamental to optimize recovery, specifically aiming for a 4:1 carbohydrate to protein ratio to optimize glycogen replenishment and enhances aerobic endurance performance by 24%.
Finally, HIIT workouts are very challenging and should only be done 2 to 3 times a week. One suggestion would be to perform them on your days off from strength training.
Example of HIIT Training
Here is an example of sprints that are just below your VO2 max and include an adequate recovery period. (Can be done outside or on a treadmill)
- Warm up at a comfortable intensity for 5-8 minutes.
- Perform a sprint at approximately 80% of your maximum intensity for 45 seconds to 1½ minutes.
- Follow this with a 1- to 2-minute recovery period.
- Repeat this sequence for 5 to 8 intervals, making sure to finish with a 5 minute cool down jog.
