Endurance athletes know that starting exercise with glycogen stores fully loaded makes for higher intensity workloads and overall better performance during competition. But, this long-held belief of sports nutrition is now being challenged!
New research points out the benefits of periodically training with low glycogen stores. Termed the ‘train low-compete high concept‘ – meaning train in a glycogen depleted state and compete with high glycogen stores. This is an interesting concept that has left many coaches and athletes scratching their heads wondering what it is all about!
From a cellular perspective training adaptations are the consequence of the accumulation of specific proteins required for sustaining energy metabolism during and after a series of exercise sessions (Hawley & Burke, 2010). However, it has been uncertain whether it is a lack or surplus of a substrate that triggers the adaptation (Coyle, 2000). New molecular insights show that compared with high muscle glycogen content, an acute bout of endurance exercise completed with low muscle glycogen results in a greater transcriptional activation of oxidative enzymes involved in carbohydrate (CHO) metabolism (e.g. AMPK & GLUT4) and an increase in adaptive responses favouring fat metabolism (Hawley et al, 2011). This convincing evidence of enhanced cellular adaptation, following training in a low CHO state triggered the innovative ‘train low-compete high’ concept.
Hansen et al (2005) conducted the initial investigation into this concept. The 10 wk training study required previously sedentary men to train one leg with a ‘two a day’ training protocol every second day, whilst the opposing leg undertook the same workouts, once every day. The ‘train low’ leg (2x a day every other day), showed significantly greater increases in time to exhaustion accompanied by greater maximal activity of the enzymes: citrate synthase and haloacid-dehalgenase (HAD). These findings have significant scientific merit and possible application for exercise programmes targeting metabolic improvements and health outcomes, however the application of this strategy to improving endurance performance appears to be inconspicuous!
Muscular adaptation achieved by training provides part of the process by which athletes improve their ability to perform. However, changes in muscle physiology are not necessarily a trigger for performance improvements and currently there is no convincing evidence that train low strategies achieve an enhancement of performance over a conventional diet/training approach (Hawley & Burke, 2010). The lack of evidence supporting the application of the train low concept for enhancing endurance performance could be due to the reduced self-selected intensity seen with having low glycogen stores.
Science2Sport raises a question???
Evidence shows that a CHO mouth wash during exercise can significantly improve endurance performance. The suggested mechanism behind this is thought to be related to the effects on the central nervous system (CNS). Glucose, is the brain’s only source of fuel and when limited (e.g. during prolonged exercise), the CNS will signal for glycogen utilisation in the muscles to be reduced, in order to spare glycogen (glucose) for the brain. This sparing of glycogen reduces the intensity an athlete can work at, thus a reduction in performance is seen. The CHO mouthwash can act as a signal to the CNS that the body has sufficient CHO stores and therefore will inhibit the signal to induce glycogen sparing, allowing the athlete to maintain a high intensity. Science2Sport asks if the elevated cellular adaptations, associated with the train low protocol could enhance performance, with the aid of a CHO mouthwash?
Potential limitations of the train low concept:
- Reduced self-regulated training intensity?
- Increased risk of injury when glycogen depleted?
- Increased risk of illness?
Do not shift to an overall diet of minimal CHO intake:
Endurance athletes will hamper performance and potentially their health by having a low CHO diet. The train low protocol should be strategically implemented. Below are some ways on how to train low, without having a low CHO diet:
- Place training sessions close together (e.g. 2x a day every other day)
- Exercise after an overnight fast
- Consume water during prolonged exercise
If you want to incorporate the train low strategy into your training sessions the bottom line is to do it wisely. For example, early in your training cycle, when you are establishing your endurance base and the exercise intensity is low, train low periodically (about 1–2 times per week) to help maximize aerobic adaptation. Build up duration and intensity slowly when training low. As you build up and prepare for increased speed with short speed workouts: while maintaining high mileage, train high, i.e., have high glycogen stores, before your high-intensity speed work; train low, i.e., in a glycogen-depleted state, periodically before endurance workouts. In the latter phase of your training — that time when you transition toward longer-duration speed workouts and decreasing mileage: train high, i.e., have high glycogen stores, in the morning before your speed work; incorporate a same-day second endurance workout in a glycogen-depleted state a few days per week.
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Tune in next week to read how some athletes are bending the anti-doping rules to their advantage!