Exercise and training routines have many benefits: improved mood, strong muscles and bones, weight management, and reduced risk of chronic diseases, among others. But big training weeks without adequate recovery can negatively impact health and performance, and even your immune system. Here we’ll take a closer look at how training load—or the amount you exercise—can impact your immune system, and what you can do to stay healthy.
High training load+psychological stressors= illness/injuryWhether you’re exercising with a competition in mind or just for everyday life, it’s important to be mindful of training load to avoid illness and injury. Training load is defined by the International Olympic Committee as, "the sport and non-sport burden as a stimulus that is applied to a human biological system over varying time periods and varying magnitude." Quite a mouthful! Essentially, training load includes both the physiological and psychological stressors that impact our bodies and the way they function.
A rigorous training load can create positive results—namely
increased performance. But it's certainly possible to overdo it. An excessive training load can result in acute fatigue, overtraining syndrome, subclinical immune changes, and illness or injury. And don't forget about those psychological stressors! Even if you're able to crush your physical training, excess stress in your personal life may demand extra recovery time to stay healthy.
Some of the most important risk factors for illness or injury in athletesWhile we can’t always prevent illness, it is important to be aware of certain risk factors that increase your chances of becoming sick:
- Season: Autumn and winter cold and flu season 
- Poor hygiene and exposure to sick people
- Recent symptoms of illness 
- Air travel 
- Poor sleep 
- Life stress, depression, and anxiety 
- Low energy availability 
- Increases in training load [1,3]
How to avoid an excessive training load—and getting sick or injured
Check in with your life stressors each week
Do you have a new project at work? Experiencing a big change in your home environment? Feeling overwhelmed juggling your family/social/work life? During these weeks, consider backing off your usual training and implementing more recovery.
Significant life stressors in combination with heavy training increases the risk of impaired immunity. Opt for activities that reduce stress such as yoga, meditation, or active recovery like walking with friends or family. Be mindful and find ways to manage and reduce stress with your training routine.
Monitor your training load and take rest days
Keep track of your exercise frequency and intensity each week. A strenuous training load is certainly important for performance adaptations, but adequate recovery time is essential. Recovery allows your body to restore homeostasis—or balance itself out—at a progressively higher level of fitness as training load ramps up.
The appropriate training load for healthy performance gains will be different for everyone. A good rule of thumb is to increase training volume by increments of 5-10% per week, especially in the winter months. Some subjective signs you might be falling short on recovery time? Fatigue, a plateau in your fitness gains or ability to perform your workouts, illness, and injury. Adding active recovery into your routine is just as important as higher intensity work!
Get your blood tested
While there are subjective measures of appropriate training and recovery, certain blood biomarkers can you give you an accurate, objective picture of how your body is responding. These include hsCRP and white blood cell count (WBC), which are both related to inflammation and immune health. Other biomarkers such as cortisol, creatine kinase, and cortisol:testosterone ratio can help indicate whether you’re getting adequate rest and recovery to see training improvements.
Eat a balanced diet and supplement when necessary
It’s no secret that active individuals have substantial caloric needs, but it is also important to consider diet composition—namely macronutrients and micronutrients— to promote recovery, prevent injury and maintain a strong immune system. A recent study in the Journal of Science and Medicine in Sport of athletes preparing for the 2016 Olympic Games found that low energy availability was significantly associated with illness. 
If you are prone to illness or travel frequently, consider taking probiotics to promote immune health. Additional supplements that can reduce the burden of illness include vitamin D and vitamin C for their anti-inflammatory and antioxidant properties. We always recommend that you consult your healthcare provider and your bloodwork before starting any new supplements.
Get enough sleep
Individuals who have shorter night sleeps are more susceptible to catching the common cold. Consistently getting 7-8 hours of quality sleep will provide your body with adequate rest and recovery time to repair itself.
A summary of training load's impact on illness and injuryWhile we can’t always avoid getting sick, there are things we can do to keep our immune system strong to stay on track to reach our fitness goals:
- Eat a balanced diet with enough calories, macro- and micronutrients
- Prioritize sleep!
- Make sure you add active recovery and rest days to your training routine.
- Practice stress management and recognize when there is additional stress in your life.
- Exercise promotes a healthy immune system but like many other things, too much of a good thing isn’t always better! Aim to find a balance in your training to see the benefits without any negative outcomes.
- Listen to your body! You know your body best—if you’re getting sick or injured often, it might be time to rework your routine.
- Getting your blood tested with InsideTracker will show you just how your body and immune system is responding to your training and active lifestyle.
Stevie Lyn, MS, RDStevie Lyn is a Content Strategist and Team Nutritionist at InsideTracker. As a Registered Dietitian and Ironman triathlete, she enjoys combining these passions to help educate others on how to fuel for overall health and performance. When she’s not swimming, biking, or running with her dog you’ll find her in the kitchen working on a new recipe to improve her biomarkers.
 Schwellnus, M., Soligard, T., Alonso, J.-M., Bahr, R., Clarsen, B., Dijkstra, H. P., … Engebretsen, L. (2016). How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. British Journal of Sports Medicine, 50(17), 1043–1052. doi: 10.1136/bjsports-2016-096572
 Philippe Hellard, Marta Avalos, Fanny Guimaraes, Jean-François Toussaint, Pyne David. Training-Related Risk of Common Illnesses in Elite Swimmers over a Four-Year Period. Medicine and Science in Sports and Exercise, American College of Sports Medicine (ACSM), 2015, 47 (4), pp.698-707. ⟨10.1249/MSS.0000000000000461⟩. ⟨hal-01099379⟩
 Hausswirth, C., Louis, J., Aubry, A., Bonnet, G., Duffield, R., & Meur, Y. L. (2014). Evidence of Disturbed Sleep and Increased Illness in Overreached Endurance Athletes. Medicine & Science in Sports & Exercise, 46(5), 1036–1045. doi: 10.1249/mss.0000000000000177
 Drew M, Vlahovich N, Hughes D, et al. Prevalence of illness, poor mental health and sleep quality and low energy availability prior to the 2016 Summer Olympic Games. British Journal of Sports Medicine 2018;52:47-53.
 Walsh, N. P. (2018). Recommendations to maintain immune health in athletes. European Journal of Sport Science, 18(6), 820–831. doi: 10.1080/17461391.2018.1449895
 Drew, M. K., Vlahovich, N., Hughes, D., Appaneal, R., Peterson, K., Burke, L., Waddington, G. (2017). A multifactorial evaluation of illness risk factors in athletes preparing for the summer Olympic Games. Journal of Science and Medicine in Sport, 20(8), 745–750. 10.1016/j.jsams.2017.02.010
 Prather, A.A., et al. Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep, 2015. 38(9): p.1353-9.