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August 27, 2023 9 min read

It is evident that while athletes pursue the pinnacles of human performance, there is an inherent risk of injury and potential illnesses. These adversities can potentially restrict athletes to bed rest and rob them of their hard-earned fitness.

Although there is some research demonstrating the effect of bed rest on physical performance in general populations(1), there is no review articles that specifically addresses athletes. This is troubling because evidence shows that those entering bed rest with the greatest physical performance level experience the greatest decrements in performance(1).

It’s shown that those with higher aerobic capacity before going on bed rest experience greater absolute losses in aerobic capacity after bed rest when compared to those that are less trained(2).

Therefore, it is plausible that athletes may be more susceptible to the detrimental effects of bed rest than general populations.

It seems that the greatest rate of decline in performance occurs in the early stages of bed rest and is much more dramatic in athletes compared to general population. This further suggests that athletes might require longer periods of rehabilitation than lesser-trained individuals(3).

There is a lack of understanding and clear direction for clinicians, scientists, and the sporting community of the consequences of bed rest specifically for athletes. In addition, recommendations for how to treat athletes during and following bed rest need clarification. Recent work examined some very key areas important in this area(3).

This article will examine the evidence on:

  1. The effects of bed rest on physical performance in athletes
  2. Identify potential countermeasures to offset bed rest-induced decrements in physical performance
  3. Provide timelines of recovery following bed rest, which could serve as the basis for evidence-based return-to-sport rehabilitation.

Major findings on the effects of bed rest on physical performance
It’s quite surprising that there is no data on elite athletes confined to bed rest, which hampers the scientific community form making evidence-based recommendations to the medical, scientific, and sporting communities.

The following findings and recommendations are drawn from research completed on regularly exercising individuals; not elite athletes at the pinnacle of their respective sports. Therefore, drawing direct conclusions relevant to higher-standard athletes is difficult.  

Nonetheless, there are some general conclusions that can be made from the research to date.

The evidence indicates that endurance exercise performance, VO2max, and lactate threshold decline after just 3 days of bed rest. Moreover, it seems that athletes with the highest initial VO2max experience the greatest loss and that endurance-trained subjects had significantly larger decrements in VO2max and lactate threshold than sedentary subjects(4).

These findings indicate that athletes are more susceptible to the negative consequences of bed rest than their lesser trained counterparts.

Two general conclusions emerge from the research on endurance performance decrements. First, VO2max rapidly deteriorates during the initial 1–2 weeks of best rest; subsequently, the rate of decline decreases(3).  

The mechanism explaining the rapid, initial decline in VO2max is that it is simultaneously accompanied by a concomitant decrease in plasma volume, thus reducing cardiac output during exercise(2).

Thereafter, the slower decay in VO2max is due to a combination of cardiovascular structural changes as well as muscular changes, such as reduced oxidative enzymes. In addition, bed rest more profoundly affects upright exercise than supine exercise. The reason for this is that, following bed rest, upright exercise elevates heart rate and decreases stroke volume to a greater extent than supine exercise, because of gravity on body fluid distribution(2).
 
It’s very clear from the preceding evidence that there are significant reductions in muscle mass following bed rest.  

The mechanism behind this reduced muscle mass during bed rest includes disuse-induced reductions in muscle protein synthesis, both while in a fasted state (as normally encountered during an overnight fast, for example), as well as following feeding. Although there is not a lot of data on loss of muscle strength in athletes; the available data indicates that bed rest reduces muscle strength within 5 days(5). Therefore, countermeasures to offset bed-rest induced decrements in muscle performance are warranted.

Probable countermeasures to offset bed rest-induced decrements in physical performance

It’s very well known that exercise is extremely beneficial for mitigating decrements in physical performance in both recreational and elite athletes. The research also supports the utilization of exercise as a protective measure of physical performance during bed rest(6).

In the case of an injury or illness to an athlete, exercise countermeasures might not always be feasible. 

The only studies examining non-exercise countermeasures all involved fluid/salt supplementation. The research in this area utilized a daily dose of fluid/salt supplementation of 26-30 mL water per kg body mass and 0.1 g sodium chloride per kg body mass.  Interestingly, fluid/salt supplementation completely preserved and significantly increased supine VO2max values during bed rest; most likely due to the maintenance of plasma volume(7).

More research needs to be completed in this area in order to corroborate these findings.

There are several countermeasures available that assist in maintaining muscle strength during bed rest. For instance, some countermeasures protect muscle strength by exposing mechanical tension within the muscle, which stimulates muscle protein synthesis(6).

Other mechanisms to stimulate mechanical tension within the muscle are:

  • Passive mechanical loading (i.e., 2.5 h of continuous passive motion using a machine, performed four times per day for an overall total of 10 h of loading)(8).
  • Electrical muscle stimulation (i.e., 30–45 min per session performed during three to five sessions per week)(6)
  • ‘Anti-gravity suits’ (for 10 consecutive hours per day)(1)

All these mechanisms demonstrate some effectiveness for preserving muscle size and strength during bed rest.

Similarly, protein ingestion (e.g., 16.5 g essential amino acids plus 30 g carbohydrate given 3 times per day; or 0.06 g of leucine per kg of body mass per meal stimulates muscle protein synthesis, thus supporting dietary protein supplementation as another non-exercise countermeasure(6).

In addition, some research has also found that producing intramuscular metabolic stress via passive blood flow restriction (5 sets of 5 min of occlusion performed on 2 sessions per day) can preserve muscle mass and strength during immobilization(9).

It’s evident from the literature that loss of muscle mass during bed rest typically coincides with loss of muscle strength, but research also indicates that changes in neural factors also contribute to strength loss(10). There is some very exciting and interesting research showing the benefits of motor imagery training. Mentally performing resistance exercise (also known as ‘motor imagery training’) involves similar neural activation as actually performing resistance exercise(11).

Interestingly, there is quite a large body of evidence indicating that motor imagery training (mentally replicating strenuous resistance exercise sessions, performed during multiple sessions per week) can enhance strength in otherwise healthy individuals(11), as well as help preserve strength during immobilization(12). Therefore, motor imagery training represents an intriguing countermeasure for preserving muscle strength during bed rest.

Preserving orthostatic tolerance might be another key for maintaining physical performance during bed rest.

When standing, gravity pulls fluid from our body towards our lower extremities; however, when we are horizontal during bed rest, our body fluid redistributes more centrally. The continued decrease in orthostatic stress during bed rest generally results in orthostatic hypotension (i.e., low blood pressure) when returning to an upright posture after bed rest is over(1).

However, utilizing a technique called lower body negative pressure during bed rest simulates the effects of gravity and causes associated orthostatic stress. Therefore, utilizing lower body negative pressure during bed rest (one or more daily sessions of ~ 15 min at approximately − 30 to − 50 mmHg) lessens the orthostatic hypotension that occurs when the individual returns to an upright posture(1).

Pharmacological agents represent another classification of non-exercise countermeasures for athletes confined to bed rest.

For example, in addition to lower body negative pressure, pharmacological agents might also defend orthostatic tolerance during bed rest. Pharmacological interventions previously used to maintain orthostatic tolerance during bed rest include atropine, propranolol, clonidine, ephedrine, indomethacin, fludrocortisone, and midodrine(11).

In addition to orthostatic tolerance, the effectiveness of pharmacological agents (e.g., testosterone) for preserving muscle mass and strength has also been explored. In general, testosterone maintains lean body mass but does not appear to help maintain muscle strength during bed rest(13).

Importantly, though, athletic doping laws must be considered when using pharmacological agents (e.g., testosterone, ephedrine, atropine) to maintain physical performance during bed rest.

Multiple physiological systems are affected by bed rest and each physiological system affects physical performance in a unique way.

There may be a potential benefit of combining multiple countermeasures to simultaneously offset bed rest-induced plasma volume losses (e.g., fluid/salt supplementation), orthostatic hypotension during upright exercise (e.g., lower-body negative pressure), muscle atrophy (e.g., protein supplementation, passive mechanical loading, passive blood flow restriction, electrical muscle simulation, and/or ‘anti-gravity suits’), and deficits in neural drive to muscle (e.g., motor imagery training) could all be used to more fully maintain physiological attributes and thus physical performance. There might be a potential for a synergistic effect from combining multiple strategies. Therefore, clinicians and scientists should consider combining multiple countermeasures to protect performance during bed rest(3).

Recovery of Physical Performance Following Bed Rest

Recovery of endurance capacity following bed rest is related to the duration of bed rest as well as pre-bedrest fitness levels. Evidence indicates that short durations of bed rest (approximately 2 weeks) require approximately 1 week of recovery, but longer durations of bed rest might require 2–4 weeks for full recovery. Also, those with higher initial endurance levels need more time to recover (2).

In reference to neuromuscular performance, research shows that 14 days of re-ambulation plus resistance exercise was sufficient to completely recover muscle strength (but not muscle size) following 28 days of best rest(14). However, 14 days of re-ambulation alone (without resistance exercise) was insufficient to restore muscle strength. It’s recommended that approximately 2–4 weeks of progressive rehabilitation (including strength training) is needed in order to restore muscle strength, as well as endurance exercise, following bed rest of ≤ 28 days(3).

As there is no date on higher-performing athletes, it’s important to note that higher-performing athletes who are confined to bed rest for medical reasons might require longer rehabilitation to fully restore physical performance following bed rest(3).

Fig: Summary of the effects of bed rest on physical performance in athletes(3)

Practical Recommendations

There are several evidence-based recommendations for practitioners who care for athletes during and following bed rest. Firstly, it is important for the medical staff to consider the underlying reason for bed rest (e.g., injury or illness) as well as the corresponding interventions necessary to treat the injury/illness (e.g., medication, surgery).

After considering these variables, the medical staff can choose from an array of potentially effective countermeasures, including fluid/salt loading, passive mechanical loading, protein supplementation, motor imagery training, passive blood flow restriction, electrical muscle stimulation, lower-body negative pressure, and ‘anti-gravity suits’ that apply continuous resistance.

It’s advised to prioritize interventions that have a high likelihood of being effective combined with a low probability of producing further harm (e.g., following musculoskeletal injury, motor imagery training presents a high likelihood for preserving muscle strength combined with a low likelihood of exacerbating the underlying injury.

Another important consideration is that following bed rest, the sports medicine and strength and conditioning staff should collaboratively design a rehabilitation program of appropriate quality, quantity, and duration. In general, following bed rest of ≤ 28 days, it is recommended that at least 2–4 weeks of progressive rehabilitation (including strength training) to restore physical performance. An important caveat is the underlying reason for bed rest (e.g., illness or injury) which will dictate the recovery timelines that are needed.  


References:
1.    Pavy-Le Traon, A., et al., From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006). Eur J Appl Physiol, 2007. 101(2): p. 143-94.
2.    Lee, S.M., et al., Aerobic exercise deconditioning and countermeasures during bed rest. Aviat Space Environ Med, 2010. 81(1): p. 52-63.
3.    Spiering, B.A., J. Weakley, and I. Mujika, Effects of Bed Rest on Physical Performance in Athletes: A Systematic and Narrative Review. Sports Med, 2023.
4.    Smorawinski, J., et al., Effects of 3-day bed rest on physiological responses to graded exercise in athletes and sedentary men. J Appl Physiol (1985), 2001. 91(1): p. 249-57.
5.    Marusic, U., et al., Nonuniform loss of muscle strength and atrophy during bed rest: a systematic review. J Appl Physiol (1985), 2021. 131(1): p. 194-206.
6.    Nunes, E.A., et al., Disuse-induced skeletal muscle atrophy in disease and nondisease states in humans: mechanisms, prevention, and recovery strategies. Am J Physiol Cell Physiol, 2022. 322(6): p. C1068-C1084.
7.    Zorbas, Y.G., et al., Plasma volume and biochemical changes in athletes during bed rest chronic hyperhydration. Acta Astronaut, 1999. 45(12): p. 747-54.
8.    Llano-Diez, M., et al., Mechanisms underlying ICU muscle wasting and effects of passive mechanical loading. Crit Care, 2012. 16(5): p. R209.
9.    Cerqueira, M.S., et al., Effects of blood flow restriction without additional exercise on strength reductions and muscular atrophy following immobilization: A systematic review. J Sport Health Sci, 2020. 9(2): p. 152-159.
10.    Siddique, U., et al., Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-analysis. Sports Med, 2020. 50(6): p. 1107-1128.
11.    Paravlic, A.H., et al., Effects and Dose-Response Relationships of Motor Imagery Practice on Strength Development in Healthy Adult Populations: a Systematic Review and Meta-analysis. Sports Med, 2018. 48(5): p. 1165-1187.
12.    Clark, B.C., et al., The power of the mind: the cortex as a critical determinant of muscle strength/weakness. J Neurophysiol, 2014. 112(12): p. 3219-26.
13.    Zachwieja, J.J., et al., Testosterone administration preserves protein balance but not muscle strength during 28 days of bed rest. J Clin Endocrinol Metab, 1999. 84(1): p. 207-12.
14.    Brooks, N., et al., Resistance training and timed essential amino acids protect against the loss of muscle mass and strength during 28 days of bed rest and energy deficit. J Appl Physiol (1985), 2008. 105(1): p. 241-8.

Dr. Paul Henning

About Dr. Paul

I'm currently an Army officer on active duty with over 15 years of experience and also run my own health and wellness business. The majority of my career in the military has focused on enhancing Warfighter health and performance. I am passionate about helping people enhance all aspects of their lives through health and wellness. Learn more about me