Uphill sprints activate the fast-twitch fibers in your legs.
Uphill sprints are a form of resistive training or sprint loading. Unlike running flats, racing up an incline forces you to work against the weight of gravity. According to coach Brad Hudson in his 2008 article вЂњRun Faster: 6 Adaptive Running MethodsвЂќ in вЂњRunning Times,вЂќ the effort of hill sprints can be equated to doing a set of Olympic weightlifting exercises. The difference is that the exercise is specific to running. By incorporating uphill sprints into your training regimen, you can build muscle and improve lower-body strength and power.
Load, Spring and Sprint
Because uphill sprints are a form of resistance training, the exercise will break down the muscles in your legs and glutes, causing small tears in your muscle tissue. The body's repair of these micro-traumas will result in building your lower body's muscle mass. Because you're sprinting on an incline, you'll need greater knee thrust with your front leg as well as push-off with your back leg to lift your body weight. The exaggerated stride will shift the pressure to your quads and calves. In addition, a sprint at maximal effort will boost the number of muscle fibers in each contraction and increase the strength and size of your fast-twitch fibers.
High-intensity Training and Hormones
In a 2011 study published in the вЂњJournal of Strength and Conditioning Research,вЂќ researchers from Kharazmi University in Iran found that male wrestlers who undertook sprint interval training experienced a rise in testosterone and a decrease in cortisol. The change in the ratio between the two hormones suggested an anabolic-type response to the training, which means their bodies were more primed to build muscle and burn fat. In this study, the wrestlers ran six 38-yard sprints with 10-second rest periods twice weekly for a period of four weeks. While high-intensity interval training doesn't raise the level of testosterone in women, it elevates the level of growth hormone and promotes the building of muscle.
Designing a Workout
Coach Hudson starts his runners on a regimen of very short sprints -- eight seconds at maximal effort on the steepest hill possible. This regimen immediately strengthens your leg muscles. As runners acclimate to this method of training, the intervals become longer, increasing to 10 seconds and then 12 seconds per sprint. If you're just starting out, look for a hill that's about 40 yards long. Perform 10 to 15 minutes of cardio and dynamic stretches, such as leg swings and squats. When your body is fully warm, try five sprints at 75 percent of your maximal effort, walking down the hill to recover from each sprint. Finish the session with a 10- to 15-minute cool down. Gradually increase each session by one or two sprints per week until you're doing 20 sprints at maximal effort, according to the Breaking Muscle website.
The 10-Second Limit
According to coach Hudson in Marc Bloom's 2007 article, вЂњQuick AscentвЂќ in вЂњRunner's World,вЂќ he limits hill sprints to 10 seconds. If you sprint over 10 seconds, your body will start producing lactate, which leads to fatigue and increases the risk of injury. Because hill sprints are a form of resistance training, allow your muscles 24 to 48 hours to recover. When identifying hills for a workout, try and choose terrain with packed turf or mowed grass. The next best option is a paved incline that's clear of traffic or other obstacles.