Updated: Nov 27, 2018
Some sports injuries have very obvious causes - you step in a ditch and sprain your ankle or you forget your feet are clipped in and fall off your bike. But what about those aches that suddenly appear half way through a run? Or the Achilles that stiffens up 2 hours after training? To understand why we suffer these sports injuries with their "mysterious" causes, one has to first understand how the body reacts to exercise.
The body has an immediate response to exercise as well as a long-term response.
Immediate response to exercise:
This is the cells' short term reaction (up to approximately 48 hours) to exercise. Hormones are secreted, energy stores are used up and has to be restored etc.
Long term response to exercise:
This involves structural and functional changes to the tissue. For example muscle fibres get bigger during long-term strength training or your heart and lungs get fitter during prolonged endurance training.
The body’s immediate response to exercise can be explained at the hand of the supercompensation cycle which is divided into 3 stages:
Fatigue (your cells run out of energy, develop micro-damage etc.)
Recovery (the cells start to repair and replenish energy stores)
Adaptation (your cells "super" compensate in case you expect them to do more exercise)
Fatigue phase (Your cells are tired out)
When you exercise, the body uses energy stores at higher rates than at rest. Your body starts to fatigue and your performance starts to decline as the energy stores are depleted. By-products accumulate and the cells suffer micro-damage.
The micro-damage can increase to the point where it causes an injury if you ask your muscles, tendons, ligaments or bones to cope with a load that is above their physical ability (you haven't trained it for it). For example if you pick up a weight that is too heavy, run too far or too fast.
You are also at more risk of being injured when you become fatigued. Fatigue may cause your muscles to lose their ability to absorb the shock during exercise and can lead to your ligaments or joints taking more strain.
Nutrition also plays an important role during this phase. You will fatigue much faster if your energy stores are not at optimal levels to start with. You can further delay fatigue by taking on food and drink while exercising.
Recovery phase (Your cells have to recover from training)
The name is pretty much self-explanatory. Once you finish your exercise session, the energy stores have to be refilled, by-products removed and micro-damage repaired to prevent more serious damage.
You increase your risk of injury if you train while your body is still in the recovery phase. If you do this too often, it may even lead to overtraining syndrome, a condition that can take months to recover from.
Different activities of varying intensities require different recovery times. Muscle can take between 24 and 36 hours to normalise after resistance training, while between 10 and 48 hours are required to replenish glycogen stores after aerobic exercise.
Certain hormones, e.g. testosterone, can enhance recovery, which is why men generally recover quicker than women. Athletes younger than 18 years and older than 25 years also require longer rest periods to reach the adaptation phase.
Trained athletes usually require less time to recover since their bodies have adapted to high training loads and have become more efficient over time. Novice runners, for instance, should really not run more than 3 times a week, while professional triathletes can cope with having just one rest day in 10!
Getting your nutrition strategies right during this phase is as important as rest. Recent research suggests that you benefit most from consuming a combination of protein and carbohydrates within 30 minutes of completing exercise.
Restricting your energy intake (not eating enough) between training sessions means that the body cannot repair the damaged cells. In extreme cases it may have to break down muscle and bone just to survive. Stress fractures are a good example of an injury that can develop due to athletes not eating enough.
The environment, travelling and sleep can also influence your recovery from exercise.
There is no one size fits all when it comes to recovery and it is worth consulting an experienced coach or sports physiotherapist if you think you may be overtraining.
Adaptation phase ( Your cells are ready to train and stronger than before)
This phase is the most important phase for training. During this phase the body rebuilds itself and replenishes its energy stores to a higher level than before your previous exercise bout. You will see the best training results if you can time your next exercise bout to fall in this phase.
Summary: What causes sports injuries?
Sports injuries are caused by:
Doing more exercise than what you have prepared your body for e.g. lifting a weight that is too heavy, running too far or suddenly doing a very hilly run.
If you do not give your body enough time to recover between training sessions. The result is that different tissues in the body (bone, muscle, tendons) become weaker rather than stronger. This is usually the case when you suddenly develop an injury during an exercise session that normally does not cause you trouble.
About the Author
Maryke Louw is a chartered physiotherapist with more than 15 years' experience and a Masters Degree in Sports Injury Management. You can read more about her here.