While the world deals with the spread of the COVID19 virus, CTS encourages athletes to stay active and continue with training activities, with specific considerations and accommodations to minimize virus exposure and transmission.
The Centers for Disease Control and Prevention (CDC) have the most up-to-date information on how to control community spread of COVID19 and what to do if you or someone you are caring for becomes ill. For the purposes of this document, we are going to focus on specific recommendations for athletes who are continuing to exercise during this period. For general information about the virus, how it is transmitted, how to prevent infection, and what to do if you think you are infected, please refer to the CDC’s website. We must also stress that this is a new virus and a situation no one has dealt with in their lifetime, so we are presenting the best information we have right now.
General Recommendations for Endurance Athletes
Exercising up to pre-crisis workload is recommended
The impact of endurance training on immune system function is one of the most frequently discussed topics for CTS Coaches and Athletes. It is well established that exercise supports immune function better than being sedentary. The point of contention, however, is whether high volume and/or high intensity exercise suppresses immune function to the point that infection risk increases, and if so, how to determine what volume and/or intensity of exercise is too much.
Our position and recommendations related to the impact of exercise on immune function are based largely on four often-cited review studies: “Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan” (Campbell & Turner, 2018), ”Recommendations to Maintain Immune Health in Athletes” (Walsh, 2018), “Position Statement Part One: Immune function and exercise” (Walsh et al., 2011a), and “Position Statement Part Two: Maintaining immune health” (Walsh et al., 2011b). While the position statements are from 2011, they are comprehensive looks at immunity and athletic training and more recent papers from Walsh, Campbell, Turner, and Gleeson support the findings from 2011.
Exercise redirects – rather than suppresses – immune resources
One of the main points of Campbell & Turner’s review is that acutely hard exercise redirects immune system resources rather than suppressing or destroying them. Following exhaustive bouts of exercise, levels of leukocytes (white blood cells) in the bloodstream drop significantly for a period of 1-2 hours. This led to the development of the “Open Window” theory, which postulated that the drop created a window for opportunistic infections. In disputing that theory, Campbell & Turner assert that the body’s response to acute bouts of exhaustive exercise is to move lymphocytes to the most vulnerable places in the body, particularly the lungs. Among other rationales, the transient drop and rapid return of circulating lymphocytes happens too quickly to be the result of producing white blood cells to replace ones that have been destroyed.
In other words, your immune system marshals its forces the way you would expect an army to defend the fortress: mass more of troops (but not all) at the potential entry points to minimize the number of invaders that get inside the walls. When the acute danger subsides, redistribute troops to resume their normal duties.
Training Recommendations to support optimal immune function
The human immune system is incredibly robust on its own, so rather than attempting to “boost” it, athletes should take actions that enable the immune system to operate at its natural best. We recommend modifying activities and behaviors – including changes to training, nutrition, recovery, and stress management – to reduce or eliminate unnecessary stresses that reduce the natural effectiveness of the immune system. The following list contains recommendations from Walsh 2018, with CTS advice for applying them to endurance training in the presence of a virus for which we have no innate or acquired immunity, there is no vaccine, and no cure.
- Manipulate training volume and/or intensity to manage training load
In this case, for most athletes “manipulate” means maintain or reduce training load. In principle, an athlete habituated to a given workload should be able to continue at that workload without an increased risk of infection. However, with ‘stay at home’ orders in place throughout much of the world, most athletes have reduced training volume in terms of weekly training hours and the duration of their longest workouts. A recent (March 26-April 3) survey of more than 1000 endurance athletes by sports scientist Stephen Seiler illustrates this trend.In terms of training intensity, we see no compelling reason for most athletes to maintain pre-crisis training volume or increase training intensity above pre-crisis levels to compensate for the loss in training volume. With all endurance events and competitions suspended until at least early summer, we recommend focusing on maintaining fitness and bolstering the depth of generalized aerobic conditioning – both of which can be accomplished despite a modest reduction in training workload from pre-crisis levels. Athletes and coaches concerned about the potential for detraining should read this article from Coach Jason Koop, which makes the case that detraining does not happen as quickly or extensively as many athlete believe.
- Keep the size of increments in volume and intensity to 5–10% per week
For better or worse, this crisis is providing some athletes with more available time for training, and there are both opportunities and temptations to dramatically increase weekly training hours. For athletes who have more training time than usual, we recommend a conservative ramp rate for increasing training volume and/or intensity. This includes CTL, ATL, time at intensity, and weekly overall time. For relatively inexperienced athletes (training age < 5 years), weekly training workload should increase by no more than 5%. More experienced (training age >5 years) may be able to increase by 5-10% per week. Because of the curvilinear nature of acquiring fitness (additional improvements get smaller and more difficult to achieve) highly fit athletes, regardless of training age (Chronic Training Load of 80+ points for at least the past 90 days) should keep incremental increases in workload under 5%.
- Increase the frequency of shorter, spike training sessions rather than enduring fewer but longer sessions
Findings from Gleeson in 2007 indicated that acute post-exercise immune system suppression was greater following longer (>1.5 hrs) endurance activities at moderate intensities (55-75% of VO2 max). However, Campbell’s assertions from 2018 call this into question if it is true that the acute immune suppression is really just redistribution. From a coaching perspective, we often find that longer workout sessions and greater weekly volume leads to greater fatigue and requires more recovery time than shorter, more intense sessions. CTS recommends that endurance athletes continue training with a mixture of shorter, interval-based workouts and longer, endurance-paced workouts. We disagree with the assertion that all hard interval efforts should be replaced by longer, moderate endurance training.
- Implement recovery activities immediately after the most intensive training sessions. Undertake easy-moderate training sessions after each high-intensity session.
These two recommendations go hand in hand and represent best practices with or without the presence of a novel virus. Specific recommendations include:
- Rehydration to replenish fluid weight lost during exercise.
- Meal rich in carbohydrate and protein within an hour after exercise.
- Limit high-intensity interval workouts to twice per week, separated by at least one day of rest, recovery activity, or endurance-paced workout.
- Plan an easier recovery/adaptation week every second or third week of the training cycle.
Many coaches create training plans to produce progressive overload on a 3-week build, 1-week recovery pattern. This provides a good starting point from which to customize build cycles for individual athletes. During this period when we want to prioritize optimal immune system function, CTS recommends taking a conservative approach to build cycles. Shorter build cycles should be sufficient to induce adequate training stress, particularly in light of the aforementioned recommendation to focus training on the maintenance of fitness and/or the bolstering of generalized aerobic conditioning.
Lifestyle Recommendations to Support Immune Function
An athlete’s immune system function is affected by actions and behaviors throughout the day and night, not just the period immediately before, during, and after exercise. Overall, training takes up a very small portion of the total hours in a week – even for elite level athletes. There are 168 hours in a week, and most amateur and masters athletes train 8-20 hours per week. What you do when you are not working out is potentially far more important for the health of your immune system.
- Optimize Sleep Habits
Getting sufficient, high quality sleep is the best things an athlete can do to support immune function (and adapt to training). Frequently-referenced research from Cohen et al. (2009) indicated that healthy individuals who slept fewer than 7 hours per night were nearly 3 times more likely to catch the common cold than people who slept more 8 hours or more. The risk of infection was exacerbated by low sleep efficiency (amount of time in bed actually spent sleeping), which supports the notion that both sleep quantity and quality are important. To read more about optimizing sleep habits, view this article, and this one.
- Reduce Chronic Stress
Acute psychological stress and acute training stress have similar effects on immune system function: they mobilize immune system resources (leukocytes or white blood cells) to increase protection against infection. Chronic stress (psychological and/or physiological), on the other hand, reduces the overall number of immune system cells and reduces the intensity of the “call to arms” response to pathogens. (Walsh, 2011b)The COVID19 crisis is a prolonged and profound lifestyle stressor. Not only are athletes worried about their health and the health of loved ones, but families are confined to home, schools have suspended live classes, millions of people have lost their jobs, and businesses have been forced to close. These stressors cannot be sidestepped or escaped, so proactive steps we recommend for coaches and athletes to mitigate psychological stress include:
- Create daily routine: People thrive with structure, so we recommend creating new schedules for daily activities – including exercise – rather than “going with the flow”. This is even more important for athletes who are habituated to highly regimented schedules. The more rigid their pre-crisis schedule was, the more they may struggle to adapt to the sudden disruption.
- Encourage flexibility: While creating routines is a positive step, it is also important to encourage flexibility. As we do when preparing athletes for long endurance events, create a plan as well as a set of go-to responses to predictable problems.
- Create/reinforce support system: It is important to have someone or a group of people to talk to. Some of those people may be family members and close friends, but it can also be helpful for athletes to talk with someone who is not connected to their family, social group, or career. Coaches can be an important component of this support system, and should be ready to direct athletes to mental health professionals for additional support.
- Encourage stress-relieving behaviors: Guided meditation, mindfulness practices, yoga, and other mental and spiritual activities can help athletes disconnect from the constant noise in order to maintain a connection to their values and identity. When mental stress and negative thoughts become overwhelming, they tend to block out everything else and athletes lose motivation to exercise, struggle to maintain focus on training, work, or family, and perform poorly when they do exercise.
Nutritional Recommendations to Support Immune Function
Nutrition plays an important role in supporting a robust immune system, but the power of nutrition to protect athletes from infection is often overstated and oversold. It is disingenuous to promote “superfoods” or ways to “boost” immune function through food or supplements. CTS recommends the following nutrition practices to support training, general health and immune function.
- Avoid energy deficiency
More important than any specific food choices, consuming adequate energy to meet or slightly exceed total daily energy expenditure (basal metabolic rate + daily activities + exercise) is necessary for achieving positive training adaptations, optimizing post-workout recovery, and maintaining immune system health.
- Prioritize fitness over body weight
Some athletes may experience anxiety over the potential for weight gain during this time of restricted movement. While it is appropriate to help athletes reconfigure their energy intake and diet composition to account for a reduced activity level, weight loss or the prevention of weight gain should not be a primary goal during this public health crisis. Coaches should be empathetic and supportive of athletes to help mitigate anxiety or guilt over occasional emotional eating or other perceived nutritional “errors”. We encourage athletes to be kind to themselves and recognize that what you can do with your body is more important than the numbers on the scale.
- Stay Hydrated
Mucous membranes in the nose and throat don’t work as well when they’re dry, so staying hydrated helps your natural defenses work better. Maintaining a good hydration status also facilitates normal circulation within the lymphatic system, which carries infection-fighting white blood cells throughout the body.
- Maintain a varied, whole food diet rich in fruits, vegetables, and lean protein
The diet most commonly promoted year-round by Registered Dietitians trusted by CTS is still the diet recommended during this public health crisis. CTS does not recommend named diets that restrict or eliminate entire food groups – now or when the public health crisis subsides. Nor does CTS advocate the consumption of particular foods for the purpose of enhancing immune system function above its normal level.
- Rely on food, not supplements
There are few supplements that show meaningful benefits for either preventing viral infections or easing the severity of viral infections, particularly respiratory infections. Supplementation with Vitamin C, Vitamin D, and probiotics is common during periods with elevated risk of viral infections, including the common cold and influenza. While these supplements are generally harmless, CTS advocates consuming food sources of micronutrients whenever possible, as well as sunlight for the production of Vitamin D.
A note about food safety: According to guidance from the Food and Drug Administration (FDA), currently there is no evidence of food or food packaging being associated with transmission of COVID-19. The virus causes a respiratory illness, and it is presumably destroyed in the acidic environment of your stomach. That said, cooking food would further reduce risks because high heat kills viruses (and bacteria). There may still be transmission risks from handling food packaging and touching your face with contaminated hands. This article published by NPR contains recommendations from Dr. Olga Padilla-Zakour, Ph.D., director of the Cornell Food Venture Center at Cornell University, for handling takeout and groceries. This includes removing takeout food from containers, disposing of the containers, and then washing hands again before eating.
Preventing Virus Transmission in Connection with Training
We recommend following the CDC’s guidelines for preventing virus transmission during activities of daily living, including frequent washing of hands, maintaining physical distancing of at least 6 feet, covering nose and mouth while coughing or sneezing, disinfecting frequently used surfaces, and wearing a cloth facemask when out in public. We encourage athletes to take the following precautions around training activities and equipment:
- Go Solo: Take physical distancing seriously and stop riding or running in groups or anyone who doesn’t live in your household.
- Avoid the droplet slipstream: A recent white paper from Eindhoven University of Technology in the Netherlands and KU Leuven in Belgium used computer modeling to examine the flow of droplets emanating from walkers, runners, and cyclists as they move. Their models suggest that droplets follow in the wake behind the athlete, and the safe following distance increases with speed. It needs to be pointed out, however, that this was not a peer-reviewed study, it has been significantly criticized, and without more details about how the models were produced it is difficult to judge the accuracy of the results. The paper itself should not be used as the definitive answer to how runners and cyclists should interact outdoors. However, even if the extent of the danger is misstated, as athletes and coaches we have no doubt experienced instances of encountering saliva and snot from nearby athletes during rides and runs.In practical terms, there is a continuum of risk, where total isolation is best and direct contact is worst. Within this context it makes sense to minimize exposure to droplets by avoiding prolonged periods in another athlete’s slipstream. Riding or running staggered or side-by-side is likely better than single-file, but overtaking is probably best of all. When overtaking walkers, runners, and cyclists, it is best to move to the side early, complete the pass steadily, and continue at a pace that will create appropriate distancing between you and the person you just passed.
- Avoid crowded trail systems and paths: While it is great to see more people getting out for walks, hikes, runs and rides, the added traffic can lead to congestion on popular singletrack trails and multiuse paths. CTS recommends athletes schedule training in these areas at off-peak times of day, and/or using lesser-known areas. As athletes with better fitness than the mostly sedentary population, we may be able to use harder or less convenient routes so people with less fitness can have more room on easier routes.
- Training outdoors with a facemask: The CDC has started recommending people wear cloth facemasks in public, and athletes wonder how it applies to them during outdoor training. In an interview with Velonews, pulmonologist Dr. Hunter Smith recommended using a Buff-style gaiter when training in areas where you are likely to encounter other people. When training alone in open spaces, a face mask is less necessary. From the article: “Unless the trail is packed with people who cannot maintain any distance,” Smith says, “the chance of getting a lot of viral particles on an open trail with breeze blowing is slim to none.”
- Store/snack/water stops: The safest option is to align training duration with the amount of fluid and food you carry so you don’t have to stop to refill bottles or purchase food during a ride or run. If you do need to stop to refuel, wash your hands.
Campbell, John P., and James E. Turner. “Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan.” Frontiers in Immunology, vol. 9, 2018, doi:10.3389/fimmu.2018.00648.
Cohen, Sheldon, et al. “Sleep Habits and Susceptibility to the Common Cold.” Archives of Internal Medicine, vol. 169, no. 1, 2009, p. 62., doi:10.1001/archinternmed.2008.505.
“Coronavirus Disease 2019 (COVID-19).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.cdc.gov/coronavirus/2019-nCoV/index.html.
Gleeson, Michael. “Immune Function in Sport and Exercise.” Journal of Applied Physiology, vol. 103, no. 2, 2007, pp. 693–699., doi:10.1152/japplphysiol.00008.2007.
Simpson, Richard & Campbell, John & Gleeson, Maree & Krüger, Karsten & Nieman, David & Pyne, David & Turner, James & Walsh, Neil. (2020). Can exercise affect immune function to increase susceptibility to infection?. Exercise immunology review. 26. 8-22.
Walsh, Neil P.; Gleeson, Michael; Shephard, Roy J.; Gleeson, Maree; Woods, Jeffrey A.; Bishop, Nicolette; et al. (2011): Position statement part one: immune function and exercise. figshare. Journal contribution. https://hdl.handle.net/2134/10584
Walsh, Neil P.; Gleeson, Michael; Pyne, David B.; Nieman, David C.; Dhabhar, Firdaus S.; Shephard, Roy J.; et al. (2011): Position statement part two: maintaining immune health. figshare. Journal contribution. https://hdl.handle.net/2134/10586
Walsh, Neil P. “Recommendations to Maintain Immune Health in Athletes.” European Journal of Sport Science, vol. 18, no. 6, 2018, pp. 820–831., doi:10.1080/17461391.2018.1449895.
Walsh, Neil P. “Nutrition and Athlete Immune Health: New Perspectives on an Old Paradigm.” Sports Medicine, vol. 49, no. S2, 2019, pp. 153–168., doi:10.1007/s40279-019-01160-3.