Who, what & why?

Some of the most renowned sports medicine experts from around the world came together at the end of 2015 with the aim of producing an authoritative consensus statement on loading in sport, and in particular, to examine the evidence that high total loads in sport were leading to high rates of injury and illness in competitors.

The result is a two-part paper that is very dense in information but still very readable for anyone interested in what contributes to overtraining, illness and injury in sport from recreational to elite levels.

What did they do?

They analysed 30 publications that met the strict criteria required out of nearly 800 candidate papers.

As well as summarizing the evidence they also provide good definitions of frequently used terms such as overreaching and criteria for assessing the suitability of particular measurements.

What did they find?

  • It’s total load that matters

Not only training and competition, but psychological stressors and daily life hassles.

  • There is no ‘one size fits all’ strategy

Responses to total load and recovery are individual.

Biological adaptation through training and recovery cycles

  • Monitoring external load* is fundamental

In order to understand the relationship between load and risk of injury / illness scientific methods should be used to measure external load.

*External load is the total of training plus lifestyle stresses.

  • External load measures should reflect intensity as well as duration

This allows high intensity sessions to be differentiated from e.g. long slow distance.

  • Perception of external load is important

There can be differences in how an athlete perceives external load compared to what the coach intended.

  • Measure internal load

Using subjective and objective measures is critical to understanding adaptation and therefore optimal external loading.

  • Rapid changes in load increase risk

Findings are mixed on whether high absolute loads always increase the risk of injury and illness, but rapid changes in load do increase risk. The old guideline of only increasing by 10% per week has been superseded by measurement of the Acute : Chronic training load ratio.

Acute:Chronic load ratio

  • Poorly managed loads poses a variety of risks

Poorly managed loads increase the risk of tissue damage conditions such as bone stress, tendon and knee ligament, as well as decision making ability, coordination and neuromuscular control leading to increased risk of overuse injuries.

  • Too little also poses a risk

Too little load can also increase the risk of future injury by losing adaptations that made the body stronger and able to withstand high loads.

  • Psychological factors can increase injury risk

Especially increased daily hassles can increase injury risk, and training load needs to be decreased to compensate to keep the external load the same.

  • Travel across time zones increases the risk of illnesses

Researchers found that travelling across more than four time zones was associated with a 2–3 times increased risk of illness in elite rugby union players.

  • Respiratory tract infections most common competition illness

50% of all illnesses recorded at competitions affected the respiratory tract, and of these, 75% were caused by infection (with the remainder being allergy or inflammation related).

  • Performance impact lasts longer than symptoms

Short term infections reduce sports performance through several mechanisms, and fever increases fluid loss which reduces performance for 2-4 days after other symptoms have disappeared.

  • Illness occurs most frequently right before or immediately after competition

The majority of illnesses occur in the build up to, and immediately following major competition. In fact competition has been shown to be a good independent predictor of illness in athletes.

  • The consequence of ignoring infections can be severe

Training and competing with infections increase the chances of serious medical complications, and even leading to death.

  • Training load, stress and travel are illness risk factors for athletes

The combination of training load, mental and emotional stress and international travel are risk factors for illness in athletes.

  • The larger the load : recovery imbalance the higher the consequence

Total load from sports and non-sport sources form a continuum from acute stress through overreaching to overtraining and immune system damage (see diagram below). Functional overreaching takes a week to recover from, non-functional overreaching several weeks, overtraining several months and immune system damage can last for years.

Load Recovery Homeostatis

  • Listen to the body’s warning signals

Illness is often preceded by sensations of fatigue, muscle and joint aches and headaches, the immune system can often be stressed without showing symptoms.

  • Is the ability to withstand load a prerequisite to reaching the top levels?

Very high loads are traditionally associated with the highest risk of illness, but recent research has shown this to be less true with elite international athletes. The explanation may be that only those athletes able to withstand very high training loads consistently whilst maintaining an intact immune system ever get to this level.

Absolute load

Summary

This two part statement on athlete load brings together important findings on how, when and why athletes get sick and injured. As we reported in this previous post athletes who completed >80% of their planned training were seven times more likely to succeed at their event than those who took significant time out. So understanding the implications of total load and how to manage it can be critical to achieving your goals.

In the next instalment, we will summarise the main recommendations from this paper and guidelines for preventing illness.

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