For ease, accessibility and effectiveness, few workouts beat lacing up and heading out for a run, whether it's a quick sprint around the park, or a longer slog across local country trails.
Not only is running proven to build functional strength, reduce your risk of heart disease and guard against neurodegenerative disease, it's also proven to de-stress your head and give you a mental boost. Best of all, all you need is a good pair of shoes, the right supplements and some willpower.
Issues can arise, however, when some people experience knee pain when running, a condition known as runners knee. But running with runner's knee isn't impossible. And, in fact, there's little evidence that running is actually bad for your knees in the long term. As evidence shows, deal with any niggles at the start, and the benefits will far outweigh the negatives.
Running and knee damage
In a Stanford University study, runners with arthritic knees were shown to have healthier knees than non-runners after a twenty year period. In fact, only 2% of the runners had developed severely arthritic knees, as opposed to 10% of the non-runners. The data was backed up by a study in the European Journal of Applied Physiology which found that running actively decreased inflammation in the knees of test subjects.
When you walk, your knees take less of your bodyweight and aren't strengthened as much, which can lead to them quickly wearing down, especially as you get older. On the other hand, researchers posit that the continual movement of the knee when running - including loading and unloading the joint with bodyweight - helps the joint to become stronger, in the same way that lifting weights would add strength and stability to your chest or arms. Not only that, but frequent stretching, flexing and bending of the knee joint is shown to help the circulation of lubricating fluid, which in turn helps keep knee tissue healthy.
There's never been a study to show that running on its own generates arthritis or directly causes any kind of damage to the knee," says Dr Tracy Ray, an expert in orthopedic surgery at Duke University School, North Carolina. Great news, then, for those afraid that runner's knee will permanently derail their sporting ambitions, or future mobility.
However, that isn't to say all runners can pound pavement to their heart's content without feeling any adverse effects. A pre-existing injury - an ankle broken in childhood, a torn ligament or tendon - can be aggravated if it hasn't had chance to heal properly. Likewise, a poor running gait, can create uneven weight distribution, leading to pain on the inside of the knee when running, or knees that burn when running.
Professor Guillem Gonzalez-Lomas, an expert in orthopedic surgery at New York University Langone Medical Centre, stresses that "technique is important" when it comes to running, including how your foot strikes the ground, what your stride looks like, and how strong your hips are. All of these aspects should be considered, and are issues that can easily cause knee problems down the line.
The key is to spot any problems before they cause significant damage. A physiotherapist can analyse the biomechanics of your movement, and help you re-train your body to move more efficiently. Likewise, having your gait analysed at a running shop so that your new shoes can be moulded specifically to counter any imbalances is a great - and cheap - investment.
But protecting knee health isn't all about how you run, or even how often you do it. As we become more and more aware of how our bodies work as efficient and complex systems, it is becoming clear that we cannot train any particular area in isolation. By limiting your exercise to running and running alone, you neglect other areas of the body, and connective tissues that would help improve your running will be left under-developed. This could be as simple as a sprain, or something seriously lopsided in how you distribute your power. Either way, it's likely to cause issues later on.
To get around this, try alternating your running with something designed to develop flexibility, such as yoga or pilates. Adding strength via CrossFit or a range of weights-room-centric fitness classes will help, while spin classes will engage underused leg muscles to round out your abilities.