If you lead a busy life and do not have much time to spend at the gym, you may find yourself thinking you have to choose between weights and cardio. However, here is evidence that doing high-intensity cardio between your weight training sets is an effective and time-efficient way to achieve optimal fitness and improve your overall health: Weight training is mostly geared to building muscular strength. Studies have shown that performing two to four sets of eight to 12 repetitions leads to fatigue. Each weight training set is typically followed by a recovery break lasting from 30 to 60 seconds, which gives your muscles time to recover. While this approach is true for building muscle and increasing strength, you can add another activity to your workouts by using your recovery time to perform intervals of high-intensity cardio. High-intensity interval training, or HIIT, is gaining a reputation of being a safe, effective and efficient way of increasing your workout time to reap the benefits for both your muscular and cardiovascular systems. It can improve athletic performance and increase overall fitness. Immediately after completing each weight lifting set, begin a 30- to 60-second bout of high-intensity cardio such as jumping rope, running in place, jumping jacks, bench step-ups, jumping onto and off of a platform, or other activities that challenge your cardiovascular system. Allow minimal rest before and after intervals, and proceed immediately to your next weight-lifting set. Cardiovascular benefits of HIIT are equivalent to or superior to prolonged continuous aerobic training. Combining cardio and resistance training helps reduce body fat by increasing your caloric burn during your workout and increasing your metabolism for up to 72 hours post-workout. Along with improved fitness and performance, interval training can benefit health. HIIT can lead to: improved blood pressure, better cardiovascular health, better regulation of blood sugar, improved insulin sensitivity in the cells, an increased ability to break down fat, improved oxygen uptake, and increased anaerobic power. A "lack of time" is the most commonly cited reason for not exercising, HIIT may be the ideal solution for folks who are time-challenged.Bibliography: Forum.bodybuilding.com Matte. M, ‘The Effects of Cardio Between Weight Lifting Sets’, livehealthy.chron.com, July 2016.