Undernutrition: the strong road to recovery

Understanding RED-S

As metabolic energy is critical for normal functioning of the body, whenever energy availability is low for extended periods of time, this can lead to multiple unwanted effects. Dysregulation of the hormone, metabolic, blood, psychological, growth and development, cardiovascular, immunological, gastrointestinal systems and more have shown to be negatively affected by RED-S(1). Unsurprisingly, metabolic energy is critical for the function of every cell in the body, and if there’s not enough of it to go around, there are going to be consequences in every bodily system!

Even if you’re the most die-hard athlete in the world, and the health concerns are of no consequence to you, RED-S should have your attention because numerous negative outcomes are directly associated performance. As figure 1 shows, these include decreased endurance performance, decreased muscle strength, decreased training response, decreased glycogen stores, decreased coordination, and more⁽¹⁾. Obviously, this is all bad news if you want to perform at your best!

In particular, RED-S can have many negative impacts on the musculoskeletal system⁽²⁾. It can lead to reduced bone mineral density, total bone size, and thinner bones. This makes the bones less resilient to the repetitive loading present in sport, increasing the likelihood of bone stress injuries or even fractures. These are injuries that can quickly sideline athletes for extended periods of time.

When it comes to the muscles themselves, RED-S invariably induces losses in muscle strength, power, and explosive strength. This is significant as speed is a relevant factor in almost every sport. Losses in muscle function will have a direct negative impact on performance. Beyond the direct impact on performance, reduced muscle recovery and reduce muscle work capacity are often present as well. This leads to poorer training performance or poorer recovery from that training, resulting in stalled progression during training.

Figure 1: Physiological consequences and potential performance/injury implications of RED-S⁽²⁾

Recovery from RED-S

Either due to a lack of awareness, miscalculations in training load and nutrition intake, or the inability to take a more conservative approach, athletes can find themselves suffering from RED-S, and needing to take steps to recover. The most obvious course of action is restoration of optimal energy availability through reduced training loads and increased energy intake. Once optimal energy availability is restored, it’s a matter of time and patience, allowing the negative effects of impaired energy availability to be reversed.

For the motivated athlete however, this can be more challenging than training hard! Fortunately, there are steps that athletes can take to accelerate their recovery, particularly from a musculoskeletal perspective. As RED-S is associated with compromise of the musculoskeletal system, this compromise needs to be reversed, and a group of researchers have suggested that the most effective strategies for doing so are plyometric training and resistance training⁽²⁾.

By including this work, athletes can restore their bone health, their maximal strength, and their ability to produce force quickly. Patient and progressive loading of the bones and muscles will build their strength and resilience. This will reduce the risk of injury as they return to full training and performance. Just as importantly, it gives athletes something they can do and be successful with, enhancing their psychological well-being and outlook.

Effective interventions

Plyometric and strength training interventions are particularly effective because they target bodily systems that are both influential on performance, and are negatively impacted by RED-S, and which put athletes at risk for future injuries. Furthermore, this type of training expends a relatively small number of calories, allowing for its inclusion while athletes are trying to stay in positive energy balance.

When implementing plyometric and strength training program with athletes recovering from RED-S, it’s critical to start very conservatively. The authors of the paper suggest starting with as little as 30 jumps/contacts when introducing plyometrics. This work can be done almost every day, patiently progressively to 100 contacts in sets of 6-10 repetitions. The difficult of the exercises can progress over time as well. They suggest that it’s important to progress to high-impact exercises to fully stress the bone. The inclusion of multidirectional movements meanwhile can help to positively stress the bones in multiple directions.

From a strength training perspective, body weight strength exercises can be a safe and effective initial stimulus. Over time, free weights and traditional strength training exercises should be included. As strength improves, the number of sets can be increased, the number of repetitions decreased, and the loads increased to provide a continued stimulus for adaptation. Of particular importance is the inclusion of spinal loading to ensure that the bones of the spine are strengthened over time.

While plyometric and resistance training can be useful for facilitating the recovery of the musculoskeletal system following RED-S, the same approach is likely to be beneficial in reducing the likelihood of experiencing a negative impact on bone and muscle health in the first place. Of course, the primary strategy for preventing RED-S is the maintenance of optimal energy availability through appropriate management of energy expenditure and energy intake. To further safeguard against any negative impacts of intentional or unintentional decreases in energy availability, plyometric and resistance training can ensure that the bones and muscles are optimally healthy.

Practical applications for athletes

First and foremost, recovery from and prevention of RED-S comes down to energy availability. Managing training loads and consuming sufficient calories to ensure optimal energy availability is the most important step in the process. There are no tricks or hacks that can circumvent this reality. However, when it comes to the health and performance potential of the musculoskeletal system, much can be done to ensure that these systems are functioning optimally.

If one does experience RED-S, part of the recovery process should include a progressive plyometric and resistance training program. Doing so will serve to re-establish the strength and function of the bones and muscles over time, which have been significantly compromised due to low energy availability.  When done patiently, conservatively, and progressively, this process will be faster and more effective than passive rest of low levels of endurance training. For those looking to prevent the negative musculoskeletal outcomes associated with RED-S, the same strategies can be used to maintain optimal musculoskeletal health. Table 1 provides some practical guidelines for the use of plyometric and resistance training (as recommended by the authors of this new research paper) during return to performance following relative energy deficiency in sport.

Table 1: Practical guidelines for use of plyometric and resistance training⁽²⁾

References

1. British Journal of Sports Medicine 2014;48:491-497.

2. Int J Sports Physiol Perform. 2024 Jun 4;19(7):623-628.  doi: 10.1123/ijspp.2023-0532. Print 2024 Jul 1.