Why Fuelling Is So Important For Cyclists Bone Health

A few years ago, fasted training was all over the cycling media headlines as a strategy behind the success of some riders at the highest level in road cycling. Touted as a strategy to boost performance, manage a rider’s body composition, and maximise their aerobic engines.  

The idea behind the strategy is to increase the metabolic stress that training creates, leading to enhanced training adaptations (i.e. more benefit from the session, without having to do any additional training), particularly of the aerobic system/fat metabolism, which is a key energy system for any endurance athlete. However, little evidence has yet shown that implementing this strategy is beneficial to performance despite the potential benefits seen in some research at a cellular level.

Fasted training, or training low as it is often referred to, is predominately achieved through training with low carbohydrate availability; this can be achieved in a number of ways, from training before breakfast, doing a hard interval session of an evening before completing another session the following morning having not recovered glycogen stores, training twice a day where there is inadequate time to recover glycogen stores between sessions, or simply restricting carbohydrate intake during a ride or in a riders general diet.

Athletes often use this both to try and enhance training adaptations, but also to help manage body composition. It can also occur inadvertently through poor fuelling practices (i.e. not eating enough on the bike), in a bid to avoid stomach issues during training, or simply the logistical challenges of eating before or during a session.

In cycling, particularly, where sessions can easily result in riders expending enormous amounts of energy over the course of a few hard hours in the saddle, failing to fuel (i.e. fasted training) can result in riders creating considerable energy deficits often in the range of thousands of kcals, which can easily put a rider in a state of low energy availability. This is where the energy they have left over after they’ve factored in their daily energy intake is insufficient to support normal physiological function and long term, can have a number of negative consequences for an athlete health and performance.

Despite the potential advantages of under-fuelling your training in terms of training adaptations, there are often a significant number of negative consequences, which are rarely talked about or appreciated when riders forget to fuel (i.e. inadvertent under fuelling) or deliberately adopt this strategy. This can range from negative impacts on training performance, more time taken to recover and a number of health outcomes.

Nutrition can influence health, and being in a state of low energy availability for extended periods can have a direct negative impact on bone health.

A recent research paper surveyed a group of 327, predominantly elite endurance athletes; they had to train a minimum of 8 hours per week, be aged 18-35 and have competed at a national level to participate. They completed a survey evaluating their use of fasted training and their bone injury history, and how much they’ve restricted carbohydrates in their training in the past (they also checked participants could identify common carbohydrate foods!).

Fasted training was highly prevalent with 38.4% of the sampled athletes engaging in it, with men (47%) more likely to utilise it than woman (31%).

One of the key findings of the study was that those who reported using fasted training had a 1.61 times higher incidence of bone injury (e.g. stress fractures).

Whilst this association doesn’t directly prove that those additional bone injuries occurred as a result of fasted training, fasted training, it’s quite a concern, particularly given many bone injuries will have a devastating impact on an athlete season, with injuries like stress fractures, taking significant time to heal. There is the potential that the use of fasted training was against a backdrop of general poor fuelling, which would further exacerbate the impacts on bone health. 

Whilst training low is potentially a strategy that athletes can use to enhance adaptations, it needs to be very carefully managed, and the findings from this study hopefully provide some insight into why this is. A big focus of Fuel The Ride Academy is around how to optimally fuel your training, to both maintain good health and have good legs for training, so be sure to check it out above. 

Coach Ben