Cardio, Steps, and Heart Rate on a GLP-1

I have written at length about lifting, and that emphasis is correct — muscle is the whole game makes the case that resistance training is what decides how much of your loss is fat rather than muscle.

But resistance training does not do the other job, and the other job matters. This is the piece about that, plus the heart rate question I get asked constantly.

Why your resting heart rate went up

A small increase in heart rate is a recognised class effect and it appears in the prescribing information — on average, a few beats per minute. People with wearables notice it immediately, and it worries them.

The mechanism is not fully settled. Direct effects on the sinus node and autonomic changes both probably contribute. What is reasonably well established is that in people with healthy hearts it is not clinically significant, it tends to be most noticeable early, and the cardiovascular outcome data in overlapping populations is strongly favourable — SELECT followed over 17,000 patients for a mean of 3.3 years and reported reduced major adverse cardiovascular events, which is a hard endpoint that already accounts for whatever the heart rate is doing.

What is expected: a resting heart rate a few beats higher than your baseline, most obvious in the first 3–6 months.

What is not, and warrants assessment: palpitations, a racing heart at rest, a heart rate that rises sharply and stays there, chest pain, breathlessness disproportionate to exertion, or fainting. Those are not the class effect, and dehydration and low potassium — both plausible here — are among the things worth excluding.

What cardio is actually for

Not weight loss. The drug is handling the energy deficit far more effectively than any amount of running will.

Cardiorespiratory fitness is among the strongest predictors of all-cause mortality that we can measure, and it is largely independent of body weight. You can be lighter and less fit, which is a poor trade and an easy one to make accidentally on a drug that removes the appetite you were using to fuel training.

Aerobic work also improves blood pressure, insulin sensitivity, sleep quality, and mood — the last of which matters more than usual given the flatness some people describe around months three to five, discussed in food noise and mood.

What it does not do well is protect lean mass. Villareal’s trial in dieting older adults found the combination of aerobic and resistance exercise preserved function best, and that aerobic work alone did not. So this is an addition, not a substitute.

The actual targets

On steps: the 10,000 figure came from a pedometer marketing campaign, not from evidence. Meta-analyses of cohort data suggest mortality benefit accumulating up to roughly 7,000–8,000 steps a day, with diminishing returns beyond. The practically important point is that the biggest gains come from moving off the floor — 3,000 to 6,000 matters far more than 8,000 to 12,000.

Steps are also the most robust thing on this list when appetite and energy are unpredictable, because they do not require a session, a plan, or fuel.

Training on not enough food

This is the real obstacle and it is specific to this drug.

You cannot train hard on 700 calories, and appetite suppression means arriving under-fuelled is the default. People push through for six weeks, feel progressively worse, and quit — concluding they have no discipline when they actually had no glycogen.

What works:

Fuel it in liquid, 60–90 minutes ahead. A shake with some carbohydrate — oats, a banana, a scoop of carb powder — goes down when solid food will not and clears a slow stomach better than a meal does. Treat it as part of the session rather than as optional.

Train away from your bad window. Most people have a predictable 24–48 hours after their injection when tolerability is worst. Once you know your pattern you can put sessions elsewhere, or move your injection day — see what to do if you miss a dose for the mechanics.

Train earlier if nausea worsens through the day, which is common.

Take the total seriously. Persistent exhaustion is far more often inadequate intake than inadequate willpower. If you are under about 1,000 calories a day, or below 1.2 g/kg of protein, fix that before adding training volume — what to actually eat covers the structure.

Skip stimulant pre-workouts. Caffeine at 200–400 mg plus vasoactive ingredients, on a drug already raising heart rate and altering fluid status, into a slow and nauseated stomach. A plain coffee is a dose you can judge.

Hydration and the heat

Sweat losses land on top of an intake that is already short of fluid and sodium. That is a bigger deal here than for a well-fed athlete, and it is the most common reason people feel light-headed during or after sessions.

Sip through the session rather than drinking a large volume at once, and consider sodium if your sessions are long or warm — the electrolytes rankings cover what to use and the blood-pressure caveat that goes with it.

Light-headedness during exercise is worth taking seriously rather than training through, and it is more often an antihypertensive that needs reducing than a fitness problem — the reasoning is in the dizziness piece.

A realistic week

• 2 resistance sessions a week, 30–45 minutes, progressive, compound movements
• 2–3 walks of 30 minutes at a pace that makes conversation slightly effortful, adding roughly 3,000 steps each
• A step floor you hit on ordinary days, set slightly above your current average
• One session moved away from your worst post-injection window
• A shake before anything that requires effort

That is roughly 150 minutes of aerobic work plus the lifting, and it is achievable on a suppressed appetite if the fuelling is deliberate. Consistency across a year matters more than intensity in any week — and unlike the scale, fitness does not plateau at month five.