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Dr. Wells: Downhill Running: You can't resist gravity

Greg Wells PhD and Jessica Caterini BSc
6/24/2013 12:06:38 PM
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Running downhill is far more difficult than most people realize, but it can have significant benefits during training if done properly. I discovered this the hard way when I ran a marathon at Nanisivik on Baffin Island in Nunavut. The final 15 kilometres of the race consisted of a 10 km downhill section, followed by a 5 km climb to the finish. The 10 km downhill section caused me more quadriceps pain than I care to remember. I also took close to an hour to finish the last 5 km, the pain in my legs was so intense. But I now know that downhill running can be a powerful stimulus for your muscles to get stronger (even if it makes you a bit sore...).

By understanding and applying the science of downhill running, you can improve your technique and train your nervous and musculoskeletal systems to help you run faster more easily. Downhill running training will also strengthen your body to be able to handle many of the muscle stresses associated with downhill, flat and uphill running.

How Downhill Running Works

When you run down a hill, your muscles are engaged in what is known as "eccentric" contraction. This means you are simultaneously lengthening and tightening your muscle fibres at the same time. If you think about lowering a heavy weight slowly – your muscles are contracting at the same time as you lengthen your muscle. For example, imagine doing a biceps curl where you lift a weight in your hand from your side up to your shoulder. The eccentric contraction happens when your biceps is still active despite the fact that you are lowering the weight back down to your hip and lengthening the biceps muscle (lifting the muscle up by contracting and shortening your biceps is a "concentric" contraction). Under normal walking or running conditions, some of your muscles contract and stretch slightly as your leg impacts the ground. Downhill running amplifies this effect causing greater lengthening of the muscles (such as the quadriceps or calf muscles) as they absorb the impact of the foot landing on the ground. On top of this, when you run downhill, less energy is required for propulsion and yet speed is maintained or even increased!

It is the eccentric loading of the muscles during downhill running that causes more muscle fibre damage than running on flats. This may cause some delayed onset muscle soreness (DOMS) within the 24-72 hour period following the downhill workout or race. Delayed onset muscles soreness is probably caused by micro-tears in the muscle fibres, an effect that we can expect when running downhill. Downhill running also increases muscle weakness when the fibres are recovering. Researchers studying muscle strength loss after 8 bouts of downhill running at 80 per cent of a participant's maximum heart rate found a strength reduction in the knee extensors of more than 50 per cent right after the exercise. They also found that recovery was slow and even after 7 days there was still a significant reduction in strength.1

This might sound like bad news for runners, but the key finding in this research is that the physiological impact of downhill running is significant but can be a powerful stimulus for muscle adaptation. You can use downhill training to stimulate muscle growth and to improve performance! But because downhill running can cause muscle damage you need to limit this kind of training and do your best to support your downhill training session with great nutrition to provide your body with the nutrients it needs to repair and strengthen tissues. You should schedule longer aerobic or recovery runs after your downhill sessions rather than interval or speed workouts.

The other thing to keep in mind about downhill running is that it helps you learn the technical aspects of running faster. Because downhill running uses gravity rather than muscle propulsion to increase speed, we can run quickly with less effort than would normally be required. The difference in energy expenditure can be spent on holding perfect running form at faster speeds than your typical pace. Some people call this "overspeed training" or "assisted running". It is used by elite runners to practice technique and train the nervous system for increased speed. Do this type of run training carefully and under control however because you'll be running faster than you might be used to!

What The Research Tells Us

Research tells us that when you complete an eccentric movement like downhill running, there is an observed "repeated bout" effect wherein your muscles are less susceptible to damage during subsequent eccentric movements. This means that you can use downhill running to improve your ability to cope with the stresses of basic running. You can also stimulate muscle growth using eccentric exercises that challenge your quadriceps and hamstrings, such as forward or reverse lunges. These exercises will help your body to ward off the muscle damage that comes with running because your muscles will ultimately become stronger and better able to handle physical stresses.

Plyometric exercises that involve jumping or hopping are also good training for muscles because of their powerful muscle and nervous system training effects. It's similar to the knee jerk reaction you experience if your doctor taps your patellar tendon - your quadriceps and the tendons that connect the muscle to bone stretch very quickly, and the sudden lengthening of your muscle sets off what is called the stretch reflex. The stretch reflex can stimulate a powerful muscle contraction that has significant training effects! Plyometric training for downhill running could involve tuck jumps, box jumps, or two-legged hurdle hops. When performing these activities, proper technique is critical - make sure you get coaching so you learn how to do these exercises properly and that you have done the background training necessary to prevent injury.

The Importance of Technique

Maintaining proper technique is critical when you run downhill. The pull of gravity and the sensation that you are moving faster promote freedom of movement that can lead you to lose your form and may increase your risk of injury. Focus on maintaining a controlled but relaxed gait with a good posture and controlled core. The key concept is to work on decreasing the impact on your joints and muscles as much as you can.

Improve Your Performance

To take advantage of the benefits of downhill training, consider the following:

- Use eccentric exercises like plyometrics to train your muscles to handle simultaneous lengthening and contraction
- Use plyometric exercises to help your body learn to cope with landing under force and to build muscle power
- Concentrate on form when you run downhill
- Avoid doing downhill training too frequently so that your body has time to recover
- Research the profile of any race you are entering so that you know if you will be faced with a downhill section on the course and plan your training and race strategy accordingly.

As long as you are careful about how you use this important technique, you will find that there are significant benefits to training on downhills that can improve your overall performance and help you reach your goals.

References 
 Eston RG, Critchley N, Baltzopoulos V. (1994). Delayed-onset muscle soreness, strength loss characteristics and creatine kinase activity following uphill and downhill running. I Sports Sci 12:135.

Greg Wells Ph.D. (www.drgregwells.com, @drgregwells) is an Assistant Professor at the University of Toronto in the Faculties of Medicine and Kinesiology. He was the sport science analyst for the Olympic Broadcast Consortium during the 2010 & 2012 Games, and is the author of Superbodies: Peak Performance Secrets from the World's Best Athletes. Jessica Caterini is a member of the Human Physiology Research Unit in the Faculty of Kinesiology at the University of Toronto.
http://www.drgregwells.com
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Dr. Greg Wells Biography

Greg Wells, Ph.D. is a scientist and physiologist who specializes in health and performance in extreme conditions. Most recently, Dr. Wells was the on-camera sport science and sport medicine analyst for the CTV Broadcast Consortium during the 2010 Vancouver Olympics and Canada's 2012 Olympic broadcast for London 2012. Dr. Wells is currently an Assistant Professor at the Faculty of Kinesiology & Physical Education at the University of Toronto where he directs the Human Physiology Research Unit. Previously, Dr. Wells served as the Director of Sport Science at the Canadian Sport Centre where has had the opportunity to work with dozens of athletes who have won medals at Commonwealth Games, World Championships and the Olympic Games. Dr. Wells also believes that to truly understand extreme conditions you should experience them yourself. To this end he continues to build on his experiences as a former international level competitive swimmer, as a marathon runner having twice completed the world's toughest marathon 600 miles north of the arctic circle, and participated in the 11,000 km Tour D'Afrique bike race - the longest bike race in the world.

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