The Law of Specificity says if you want to get better at a certain activity, you must practice that activity repeatedly and frequently. Running is no exception. While you could log many laps in the pool and develop an efficient aerobic engine via swimming, it won't completely transfer to running. You may be fit, but if you want to become a better harrier, you must run. With that said, the Law of Diminishing Returns is also important to consider when structuring a training program. When all you do is run, you miss out on developing strength and flexibility that can contribute to healthier, faster running.
Running by itself trains relevant patterns of movement, and also strengthens running-specific muscles. Problems arise when strength imbalances begin to develop, requiring certain muscle groups to carry more of the load than they are built to undertake. This can lead to weaknesses and inefficiencies, which in turn, can develop into injuries. "We focus so much on running that we often neglect our strength," says Ryan Hill, a coach and 2:40 marathoner. "By including a strength-training component, we are able to increase our running workload without increasing our injury risk."
In the quest to strike a balance between the Law of Specificity and the Law of Diminishing Returns, high intensity circuit training (HICT) has become one of the go-to solutions for many endurance athletes. It's time efficient, customizable, and provides some nice variety to the lonely miles on the road. Better yet, it can turn you into a better runner by making you a more complete athlete and allowing you to run added mileage without injury. "A high-intensity program such as HICT offers a complete strength workout without taking too much time out of your day," says Hill. "This leaves you with more time to run."
A recent review of HICT in the American College of Sports Medicine's Health and Fitness Journal sang the praises of this approach. In addition to added strength, they also point to the wide body of research demonstrating its effectiveness for fat and weight loss, as well as increased VO2 max. "You will be able to run at a lower percentage of your muscular capacity, so running will be easier," says Hill. "The balanced strength will also help prevent injury, and make you more capable of handling a higher workload without breaking down."
HICT programs that include bodyweight-only exercises provide maximum time and cost efficiency. No need for fancy equipment and costly gym memberships. While you can tailor the exercises to known strength imbalances and weak spots, there are a number of exercises that will benefit just about any runner. As you complete your HICT workout, be sure to take only about 30 seconds of rest in between each circuit; to gain all of the benefits of this type of work, you must keep your heart rate up.