Can Your Legs Get Stronger From Running?

If you're looking to gain leg muscle, it's probably time to hit the weight room, right? Weighted squats, lunges and hip thrusters are all great moves to strengthen your lower body. But if you're more into using cardio as your exercise of choice, can running help build leg muscle?

Well, it depends. Running has been proven to improve muscular endurance and power, depending on the types of workouts you do. Hypertrophy, or enlarging your muscle size? Not as much, unless specifically programmed, according to a 2014 study in Exercise and Sport Sciences Reviews.

No matter what type of muscle gain you're hoping to achieve with running, the type of training and workouts you do play a crucial role in reaching your goal.

In order to build muscle, you need to expose your body to a new and challenging stimulus, according to the overload principle. The stressor causes a breakdown in muscle fibres called muscle protein breakdown (MPB). Then, the healing process known as muscle protein synthesis (MPS) leads to the reaction of the muscle fibres to grow back stronger. MPS happens during recovery, and with the help of proper nutrition.

And it doesn't just stop there. Depending on the type of stress, like sprints versus a long run, you can further enhance the type of muscle fibres that respond to the stimulus. For context, there are two main types of skeletal muscle fibres: slow twitch and fast twitch. Slow-twitch muscle fibres are resistant to fatigue and produce a low and slow force, whereas fast-twitch muscles fatigue a bit more easily, producing a powerful, quicker force.

What does this mean for your runs and strengthening your leg muscles? When you go for a long run, your slow-twitch muscle fibres help to sustain your pace throughout the miles. But when you do something a bit quicker, like sprint intervals, your fast-twitch muscle fibres are recruited. All of the muscles in your legs contain a mix of both types of muscle fibres, so your training programme should, ideally, include both endurance runs and powerful speed sessions to build strength and increase your fitness. Depending on your goals, you may emphasise strengthening one type of muscle fibre over another.

Typically in a beginner's running programme, the first focus will be on developing a strong base line or endurance. To do so, start by running a handful of times at a comfortable pace several days a week, if possible. It's important to begin with a series of low-intensity runs before introducing speed workouts to ensure your body can withstand the added impact that's incurred when you do speed workouts. This could be the difference between a healthy training cycle and getting injured—right from the get-go.

That's why it's important to stick to one of the main components of the overload principle: gradually introduce fresh challenges to encourage the ongoing strengthening in your muscles. After all, your body will adapt to the current load, meaning your run performance won't improve until you begin to increase the intensity, volume and frequency of your runs. Meanwhile, introducing a strength-training programme before adding in tempo runs and intervals is key for muscle hypertrophy, power, maintenance and injury prevention.

As a result of the programming, leg strength can be developed in the main lower-body muscles:

• Quadriceps: thigh muscles

• Hamstrings: back of the thigh

• Gastrocnemius and soleus: calves

• Glutes: bottom

Whether you're a new runner or seasoned vet, optimising your workouts to slowly increase time and intensity can help to improve muscular power, endurance and growth. It's somewhat simpler for a beginner to build leg muscle—each run can be approached as an opportunity to get stronger.

For people who are more familiar with hitting the pavement, workouts that include sprints, hill workouts or tempo runs can help improve leg strength. Despite where you are on your running journey, it's important to make changes to your workout routine carefully and methodically. If you do too much too soon, you might be benched with an injury.

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And while running can absolutely build leg strength, it's wise to consider supplementing your cardio workouts with weightlifting, swimming, yoga or Pilates to further target muscles that can also inform your running form, gait efficiency and bone strength.

Did you know that building leg muscles also can help your run performance? After you establish a robust endurance base and introduce a strength-training plan, you can then start adding in speed sessions to your training plan to further improve your fitness and leg strength.

Sprint intervals can be effective in building muscular power, especially. A 2017 study in the International Journal of Exercise Science found that runners who participated in high-intensity interval training (HIIT) not only improved their cardiorespiratory fitness, but the size of their quadriceps increased, too.

After participating in a 10-week interval-training programme, researchers found that the participants' quadriceps increased in size by 10 percent. A control group who did not participate in the running protocol reported no significant changes, comparatively.

The study's authors concluded that cardio (think exercises like cycling or running) can be effective for building muscle size when structured appropriately, especially when HIIT workouts are introduced.

In order to build muscle anywhere in your body, it's imperative that you're consistent with both your training and diet. Consuming enough protein is particularly important. The International Society of Sports Nutrition (ISSN) recommends that athletes consume 1.4–2 grams of protein per kg of body weight per day for building and maintaining muscle mass.

And don't forget about recovery. On the days following your interval training, make sure you give your body a break. Recovery looks different for everyone, and may even look different for you depending on how you're feeling.

For example, one week you may do some active recovery exercises including cycling, swimming or yoga—all of which help maintain range of motion in your joints but give your body time to heal and rebuild. Other weeks, you may need to take a couple of days fully off, and that's fine too. It's important to listen to your body and what it needs.

Sleep is also imperative for proper recovery from exercise, as it promotes muscle tissue growth and repair. In fact, not getting enough quality shut-eye each night has been associated with reduced muscle strength.