Gym rats/bodybuilders: Why do I get dizzy on leg day?

Started doing workouts with a trainer twice a week, and on leg days, we do leg extensions, leg curls, then leg press. I won’t say the weights because they are embarassingly low, but I am working right at my limit for all of the exercises.

When I get done with the presses (and honestly, really after my first set) I get super dizzy, my pulse races, and I feel like I’m about to pass out. It passes eventually if I put my head down, but I still feel shaky and fuzzy the whole rest of the night. It doesn’t prevent me from lifting the weight, but it feels wretched, andI worry that I really will pass out and humiliate myself.

It doesn’t happen when I do cardio, or on my other workout day - just when I work my legs. My trainer said it’s nothing to worry about, but I want to know what is happening, and he’s not big on explaining actual physical processes.


You need to talk to your doctor. It could be a sign of high blood pressure.

Which is odd, because I have very low pressure, and have had all my life, and still had when I checked with my doc before I started working out more. I run in the 90/60 range normally.

ETA - sorry, I suppose I should have mentioned that in the op.

Leg work can be highly anaerobic if you’re pushing your limits ( Reps, sets?)
Make sure you’re breathing. Holding your breath, besides raising abdominal pressure, will deprive your muscles of oxygen.

Are you new to lifting or just working with a trainer?

A real trainer should have no problem explaining physical processes. What are this guy’s qualifications?

What is your blood pressure? Sounds like you’re having a drop in pressure.

I try to breathe right - he’s good with that, so I don’t think that’s the issue.

Three sets, between 10-12 reps.

New to lifting and to working with someone.

Small town, he’s an employee of the fitness center, he’s good with directions, but he thinks I overthink this all too much. I’m not trying to overthink it (at least I don’t think I am) but it’s all new and interesting and I get curious.

I’m always low pressure, so is that just what’s going to happen because I have low pressure, or do you mean it could be dropping lower?

Going from sitting to standing can result in a brief dizzy spell.

Sounds to me like you’re going anaerobic and not getting enough recovery between sets to repay the oxygen debt.
How hard are your cardio workouts?

Wanting to know the whys and wherefores of a workout is not overthinking things. The more you know, the more effective your workouts will be because you understand the purpose and how it affects your body.

I can get a little lightheaded doing squats. I figure it’s because I’m using a lot of muscle mass as compared to upper body exercise, and I’m not breathing properly to keep the muscles oxygenated as others have pointed out.

Knowing this, I focus on my breathing, pause between reps, and pay attention to how I feel. I still push myself, but I come through the set in much better shape.

My guess - you’re bit low blood pressure to begin with. Leg days cause a large mass of your muscles to vasodilate and your body is not yet able to adapt rapidly and constrict back. Hence blood pools in the muscles, dropping your already low pressure further.

That said the concern is that hard exercise could trigger an arrhythmia and cause dizziness, so it might be worthwhile to get a screening EKG and possibly an echocardiogram. So yeah, talk to your doc.

The echo is to cross off hypertrophic cardiomyopathy.

Things the doc might want to know - have you counted your pulse when it was racing? If so how high was it? Did it feel fluttery at all? Any chest pain or strange chest sensation? Any history in your family of sudden death especially at a young age, especially of rhythm issues, of unknown cause, or drowning accidents (an arrhythmia during swim that kills gets classified as drowning).

Meanwhile, not your doc, just reacting to a hypothetical situation, but given the little information presented, really, I’d hold off on more strenuous exercise (and strenuous is defined not by absolute weight but by how hard it is for you) until your doc responds to your report of dizziness with strenuous resistance exercise. Again, likely NOT a major problem, but crossing the unlikely off the list is easy, painless, and pretty cheap.