Health Claims

Even if the air has the same oxygen level, being at real high altitude makes your body respond differently to weightlifting than breathing the same air through a mask—your muscles get more oxygen, you produce more lactic acid, and your heart works harder.

Causal

After lifting weights, your heart rate comes back down to normal at about the same speed whether you rested 1 minute or 2 minutes between sets, or whether you trained at real altitude or with a mask.

Descriptive

When you breathe oxygen-poor air through a mask for only 5 minutes before lifting weights, your blood oxygen level drops more than when you’re at real high altitude—even if the air has the same oxygen content.

Causal

Whether you rest 1 minute or 2 minutes between squat sets, your muscles get about the same amount of oxygen during the exercise, even if you're at high altitude or breathing normal air.

Descriptive

People feel much more tired after doing weightlifting with only 1 minute of rest between sets than with 2 minutes of rest, no matter if they’re at high altitude or breathing oxygen-poor air.

Causal

Whether you rest 1 minute or 2 minutes between sets, or train at real high altitude or with a mask, you can still lift the same total amount of weight without losing strength.

Descriptive

Even when the air has the same amount of oxygen, breathing it through a mask at low pressure makes your body produce less lactic acid and keeps your heart rate lower during weightlifting than being at real high altitude.

Causal

Breathing air with less oxygen through a mask (simulated altitude) makes your muscles get less oxygen during exercise than being at real high altitude, even when the oxygen level in the air is the same.

Causal

Taking less rest between sets of weightlifting makes your body work harder, raises your heart rate, makes your muscles burn more lactic acid, and feels much more exhausting.

Causal

If you're already someone who lifts weights, doing light weights twice a week until you can't do more reps can make your muscles bigger and stronger in just 8 weeks.

Descriptive

For people who already lift weights, it doesn’t matter much if you rest 30 seconds or 2.5 minutes between sets of light weights — you get the same muscle growth and strength gains either way.

Quantitative

You can get stronger and bigger muscles by lifting light weights until you're exhausted — even if you never lift heavy, which challenges the old idea that heavy weights are required.

Mechanistic

Whether you rest a short or long time between light weightlifting sets, your body releases about the same amount of growth-related hormones right after the workout.

Quantitative

Resting 30 seconds between sets of light weights builds your arm and leg muscles just as well as resting 2.5 minutes — at least in people who already train regularly.

Quantitative

If you're already trained, doing light weights with short or long breaks between sets gives you about the same strength boost in your chest and legs after 8 weeks.

Quantitative

Even though your body releases similar growth hormones after light workouts whether you rest a little or a lot, you still get stronger and bigger muscles either way.

Mechanistic

Whether you rest 30 seconds or 2.5 minutes between sets of light weightlifting, you end up with about the same muscle growth and strength gains after 8 weeks.

Quantitative

Even light weightlifting until exhaustion makes your body release hormones that are linked to muscle growth, no matter how long you rest between sets.

Quantitative

Lifting light weights until you're exhausted can make you stronger at lifting heavier weights, even if you never lift heavy.

Quantitative

Even lifting light weights really slowly until you can't do another rep can make your muscles bigger, just like lifting heavy weights.

Quantitative

When researchers measured the thickness of the upper arm at two specific spots, both spots got thicker after 12 weeks of arm workouts.

Descriptive

After doing bicep curls 24 times over 12 weeks, women’s upper arm muscles got noticeably thicker, no matter which way they did the curls.

Descriptive

After 12 weeks of training with the same total workload, neither method made the biceps noticeably thicker than the other.

Descriptive

Women who did any kind of upper-body strength training ended up with thicker biceps than women who didn’t train their upper body at all.

Descriptive