I have heard multiple times that going to the gym for about 2 hrs.+ each day often, weakens your immune system for a while, and breaks it down for a while. I would like to know if anyone has ideas to prevent this from occurring if I carry my workout through, because I want to work out 2 hours a day, 5 times a week. Any advice?

  • I'm not sure if there's any scientific reason against this; however, depending on the exercises being performed, your nutrition, and rest, your body should easily adapt to this regimen.....especially if you're young. Commented Oct 8, 2015 at 3:27
  • Hrm. It's close, I wonder if this might be a better fit on health.
    – JohnP
    Commented Oct 8, 2015 at 3:42
  • The key is to avoid total exhaustion. The kind of exercise where you can still get out of bed without major pain is more likely to keep you from getting sick. The studies showing weakened immune system response, whether in animals or humans, only shows increased risk for the sort of exercise where you never rest.
    – Sean Duggan
    Commented Oct 9, 2015 at 15:55

3 Answers 3


I'll be honest, there are some people who spend 2 hours in the gym and they accomplish less than others who spend only 45 minutes. Keep in mind that is a huge investment in time and energy, and without a great plan of attack you will end up doing too much too soon. The people who are spending 2 hours a day in the gym have built up their work capacity over time to handle the stress of that kind of work.

Managing Recovery

Managing recovery is the priority number 1 when dealing with this kind of work volume:

  • Make sure you get at least 8 hours of sleep a day. Take naps if you have to.
  • Nutrition becomes very important. You will likely need pre, post, and intra-workout fuel. Chocolate milk can be very good for this.
  • Limit yourself to only taking caffeine prior to working out. Caffeine can affect your sleep, and your natural recovery so only use the stimulant when you need to do work (coffee, sodas, caffeine pills, etc.)
  • When you are resting, rest
  • No extra work. Have your plan and execute it. Throwing in extra work can dig a deeper recovery hole.
  • Vary weight and reps throughout the week. One or two days will have higher weight with fewer reps, and the rest will have lower weight with higher reps.
  • Incorporate cooldown walks as part of your training regimen. The slow and steady cardio can help your muscles recover from the work you've done


When you are really pushing yourself, it pays to get a coach to manage your workload for you. They know how to help you navigate managing your recovery and adjust training as necessary. They also will end up pushing you harder than you would yourself.


I've never noticed this temporary immune system crash from training, however, to strengthen it so you can avoid the crash and get the most from your workouts/avoid overtraining injury, which I'd be more concerned about:

  • Sleep at least 7.5 hours (go for 9 during the first month)
  • Eat clean
  • Drink a lot of water, like a glass every few hours
  • Don't drink alcohol/don't smoke anything (just for the first month)

I'm assuming you never trained like this before, so the above will definitely get you a good start.

Good luck, avoid injury (don't get lazy and cheat on form etc/don't try to do too much)

  • Just to note, I have been training for over a year. Commented Oct 8, 2015 at 20:01
  • @RobSterach your immune system will be fine then, my best advice though would be to add BCAA's and powdered carbs as an intraworkout drink to the above listed. I used to lift for an hour before practice and I would cramp up, the drink minimized cramping/soreness. Good luck.
    – DavidR
    Commented Oct 9, 2015 at 0:33
  • @RobSterach I just ended up back here and noticed you said you plan on working out 5 days a week, are you trying to get stronger or gain endurance? 4 days a week for strength. More for endurance/cardio. More than 4 days gets you looking like a marathon runner, 4 days gets you looking like a running back.
    – DavidR
    Commented Oct 9, 2015 at 23:31
  • I used to train for 3.5 hours, 7 times a week, and it did not make me look like "a runner" at all, I was mistaken for a football player. May I ask for scientific reasoning behind your claim? Commented Oct 10, 2015 at 0:25
  • I guess by coincidence, I got sick a lot during that period of history and found out later overtraining can weaken the immune system temporarily. Commented Oct 10, 2015 at 1:28

Moderate exercise boosts your immune system, but you experience diminishing returns as you increase in intensity (one study here).

The two biggest factors that can have negative effects on your immune system are inflammation (inflammation suppresses your immune cells), and overtraining syndrome (list of symptoms to monitor).

David and Berin's answers are solid; get plenty of sleep, eat right (especially avoiding foods that cause an inflammatory response in your body), and allow yourself to recover.

The only thing I would add, especially if your going hard during those two hours, is listen to your body before, during, and after training. Consider monitoring biomarkers like HR, HRV, CNS tap testing on a daily basis; push through discomfort, but don't push through pain; and on the days you're working out, if you're not feeling it, don't kill it.

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