Garry Y. Itkin notes that the past 20 years have seen some of the best fitness trends to hit the industry. Some have been revolutionizing, while others were downright popular. In today's blog, Garry Y. Itkin looks at five of the most memorable ones.

1. High-intensity interval training or HIIT – This is a relatively new concept where people take short, intense workout sessions. The idea was popularized by Martin Gibala, who wrote the book The One Minute Workout. HIIT works on the principal of giving intensive effort for a very brief period with moderate to low-intensity exercise done during rest.

2. Wearable gadgets – Gadgets such as FitBit and Nike Fuelbands, as well as heart rate monitors like those from Polar, help people track their daily activity. The idea behind these gadgets is to make you aware of the calories burned during every activity throughout your day. This way, even activities that seem very passive can be tracked and quantified.

3. Functional fitness - This refers to training to improve sports-specific movements. Functional fitness is about training the body in the way that it's actually meant to be used. Workouts like Crossfit, which has gained popularity around the world, use functional fitness technique.

4. P90X - With this exercise regimen, you don't need weights; instead, you rely on your own body weight to perform strength-training exercises. P90X is tough, but if you can complete a series of the DVDs, your muscles will be in great shape.

5. Zumba - This fusion of international and Latin music along with effective moves has been extremely popular for years, Garry Y. Itkin mentions. It's a great way to get in a good workout while having fun.