10 Days Off + Anti-Biotics -- Significant increase in HR

I have been noodling with Trainerroad workouts since the weather got cool-cold here. I’ve been doing Z2 workouts 1-1.5 hours long and I perform them either first thing after waking in the morning or later in the day. Regardless I am not supplementing carbs ATM. In the morning, I don’t eat before the workout and typically later day rides are a few hours after my last meal/snack. I usually take plain water during the ride. In addition, I’ve started hitting the gym 3-4 times per week (bodyweight, weight machine, and stretching exercises – focusing on hips and core).

Then, I got a staph infection near (just outside it) the saddle-sore zone and I had a medical professional look at it. The Dr put me on 2x/day Bactrim routine and advised me to stop with the cycling activities until the sore resolved. In addition, I halted going to the Y since I did not want to risk infecting others. The anti-biotics, my body, and time have dealt with the infection and I am again working out.

When I resumed my program I noticed significantly higher heart rates for equivalent workouts. Example, a b4 & after workout with Whorl has me at an average HR of 121 vs 134 bpm. I expected some loss of fitness, but this is a significant change. Does that seem right?

Is there any research out there about how anti-biotics affect fitness? Does that seem right for a 10 day hiatus? It doesn’t to me.

Also worth noting is a big focus for me right now is weight-loss which is occurring having gone from 217 pounds in the early-mid summer to near 200 pounds ATM, but that was well in progress before the infection. So, the weight loss does not explain this in my mind.


Taking the antibiotics out of the equation, the 10 days of rest could very well be the cause of the bumped up heart rate. It’s very common to see where the heart rate gets “sluggish” near the end of a big training block, but then after a recovery week it both rises faster and goes higher.

Different people respond to antibiotics differently. The underlying problem being treated is also an important factor (UTI vs Pneumonia vs a Staph skin infection). The most common complaint is feeling tired.

If you are otherwise feeling well, I’d just train through things right now and listen to your body. If you legs feel good and you are hitting your targets, then I wouldn’t worry too much about the heart rate. I suspect it will sort it self out as you get a few more workouts in.


Thanks, I’m feeling well and all of that. I am carrying on!

Ten days off is likely enough for your blood volume to decrease, which is going to lead to a higher HR for similar efforts. Not really a change in fitness, just a change in how your body will express that fitness.

If your diet is fairly controlled, it isn’t that uncommon to lose weight over a 1-2 week period of zero training due to this blood volume decrease. As your body gets back in the swing of training it will add the plasma back in (along with the associated weight) and your HR should return to similar levels fairly quickly


Thanks. Indeed, my diet is well controlled for the last few months.

You’ve had an infection, and your body is likely still recovering even if you are starting to feel better. Higher HR is normal under these circumstances.

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Yeah, I guess I’ve seen changes to HR going into a bout of illness so I guess that HR effect will also show on the tail of illness too.