Interval training vs. resistance training
Resistance training involves a movement in which one's muscles or groups of muscles are used to move a moderate to heavy weight for several repetitions.
Resistance training stimulates Type IIb muscle fibres, which contributes to the development of lean muscle mass.
By having more lean muscle mass, a person will burn more calories per hour at a resting rate, than someone of the same weight with less muscle. When applied in different ways (such as with higher repetitions and shorter rest periods), it can also be an effective tool to increase endurance.
As well as this, resistance training itself heightens the trainee's metabolic rate for several hours after that person has finished exercising, and also increases bone density.
Using very heavy loads in resistance training can be dangerous and lead to injury, which can be very severe in some cases. If performed improperly, resistance training can lead to muscular imbalances and poor posture.
Interval training (commonly known as HIIT) consists of performing an activity (such as sprinting or rowing) with great intensity for a short period of time (usually no greater than 30 seconds), followed by a period of low intensity activity or complete rest for another interval (usually 30-60 seconds).
Interval training can improve glucose tolerance, reduce body fat, increase VO2 max (though this is still debated), and is more efficient than steady-state cardio, as it can improve both the aerobic and anaerobic systems to a great degree, despite HIIT workouts rarely exceeding 30 minutes.
Interval training is very easy to overdo, and like resistance training, the risk of injury is high. Sprinting, for example, can easily lead to pulled or torn muscles, so it is very important that you fully warm up before performing HIIT. Finally, it can cause extreme lactic acid build-up, which can be painful, or vomiting.
For an optimally fit, healthy and strong body, both forms of training should be used; although they both have their dangers when performed intensely, both methods can be used alongside one another.
The key to unlocking your desired results comes from correctly following these training methods, and supplementing them with a diet that is tailored to your fitness goals.