Many believe that exercise has an immunosuppressant effect. But recent scientific studies show this not to be the case. It turns out that moderate levels of high-intensity interval training (HIIT) actually boost our immune function. It leaves our bodies more able to fight off foreign invaders so we can fight off the competition on Zwift. Here we explain the science behind it and provide some sample smart trainer workouts for optimal immune function.

When we train hard, we break down our muscles. The pain and discomfort is something that we put up with for the eventual greater gain that is to come. But when it comes to our immune system, mother nature is smarter than we think. Rather than breaking it down temporarily, exercise strengthens it and leaves us better equipped to fight off infection.

WHAT DOES SCIENCE SAY ABOUT EXERCISE AND IMMUNITY?

We cyclists are very good at resting up when we feel heavy legs. But when it comes to evaluating immune function, we often have no idea until it’s too late and we’re already sniffing.

The microscopic world of cells, tissues, and antibodies that exists within us all is one best left to those with lab coats and microscopes, rather than those wearing lycra on carbon frame bikes.

Thanks to the former, we have several studies that provide some surprising findings on how exercise benefits immune function.

ACUTE EXERCISE INCREASES IMMUNE FUNCTION

A study published in Frontiers in Immunology in 2018 set about debunking the myth of exercise-induced immune suppression. Researchers came to three bold conclusions.

  1. They debunked the claim that vigorous exercise is an immunosuppressant, and claimed that exercise most likely improves immune competency across lifespan.
  2. Previous studies showed a reduction in lymphocytes (the body’s primary immune cells) one to two hours after exercise. Where scientists previously thought this signalled low immunity, researchers established that this reflects a redistribution of immune cells to other tissue rather than immune suppression.
  3. In addition to improving immune function, frequent exercise may limit or delay ageing of the immune system.

A second study published in the Journal of Sport and Health Science in 2019 shed some light on the type of exercise that benefits immune function. Researchers found that acute exercise is an immune system adjuvant that improves both defence activity and metabolic health.

Acute exercise is defined as routines of moderate-to-vigorous intensity that lasts less than 60 minutes. According to scientists, it’s this form of exercise that boosts immune function most favourably. The reason is two-fold. Firstly, it mobilises white blood cells that protect against invaders, and secondly, the stress hormones which so often compromise immunity do not reach high enough levels given the short duration of the exercise.

BUT WHY DO HARD-CHARGING ATHLETES GET SICK?

If exercise doesn’t suppress immune function, then why are the best in the world so prone to infection? After all, we all know of elite cyclists who succumb to sickness during Grand Tours.

Despite the findings that high-intensity exercise improves immune function, researchers also noted that after periods of intensified training and competition, athletes are at increased risk of infection.

The life of a professional cyclist involves several determinants that influence immune function. Factors such as travel, poor sleep (different beds every night), long six-hour races in the rain, and being in crowds all contribute to decreased immunity in elite athletes.

3 IMMUNE-BOOSTING SMART TRAINER WORKOUTS

Here are three immune-boosting workouts backed by the latest in immunology science. Intense but short, they’re ideally suited to the smart trainer and are sure to give your immune system and legs a much-needed boost.

SWEET SPOT. MAXIMUM BENEFIT, MINIMUM RECOVERY

Neither too hard nor too easy, sweet spot intervals leave athletes satisfied yet able to recover quickly. Here’s a workout that’ll blow off the cobwebs and give the immune system a much-needed boost in just 60 minutes.

  • Warm up for 15 minutes in zone 2
  • 20 minutes between 88-93% of FTP
  • 5 minutes of easy pedalling to recover
  • Another 20 minutes between 88-93% of FTP
  • Warm down for 15 minutes
ANAEROBIC CAPACITY REPEATS. BREAKING THE ELASTIC

Here’s one to tax your anaerobic capacity system that’ll leave you spent in under an hour.

  • Warm up for 15 minutes in zone 2
  • 2-minute effort at +120% of FTP
  • 3 minutes of easy pedalling to recover
  • Repeat 6-8 times
  • Warm down for 15 minutes
VO2 MAX REPEATS. HANG IN WHEN THE PACE GETS HOT

Here’s a short VO2 max HIIT workout that’ll not only help boost immune function but will also help you sit in when the pace cranks up at your next race.

  • Warm up for 15 minutes in zone 2
  • 3-5 minutes at 105-120% of FTP
  • Recover below threshold at 80% of FTP for 5 minutes
  • Repeat 5 times
  • Warm down for 15 minutes

OTHER FACTORS THAT AFFECT IMMUNITY

Immune function is a multipronged approach, and three other factors that significantly contribute to immunity include sleep, diet, and stress.

SLEEP

Sleep is critical to both recovery and immune function. When we sleep, our immune systems release proteins called cytokines. In addition to promoting sleep, these cytokines also increase when we have an infection. A lack of sleep decreases the production of these cytokines and leads to a reduction in the all-important antibodies that fight infection.

STRESS

With continual stress, our brains send out defence signals to the endocrine system to release an array of hormones that prime us for fight or flight. While this is beneficial in rare instances of real danger, in others, it only serves to severely depress immunity.

DIET

While those high-sugar drinks may well be a long-time favourite of cyclists, what few realise is that eating or drinking too much sugar inhibits immune function. A full spectrum of fruits and vegetables high in vitamins C and E, plus beta-carotene and zinc will help keep your immune system primed. Perhaps it’s time to forego the delights of the high-carb world and delve into the world of the fat-adapted cyclist!