Lab Notes · 4 min read
Conditioning is one of the six things we measure on you. It is built into the lifting itself, which is why there is no separate cardio session sitting on your schedule. Here is how that works, and why your resting heart rate comes down for it.
It is how many times your heart beats in a minute while you are doing nothing. It is the running cost of your body at idle.
Pooled across more than a million people, the higher a person’s resting heart rate, the higher their risk of dying, and the risk climbed with every ten beats.
Zhang, Shen & Qi, CMAJ 2016 (46 cohorts, n=1,246,203)
So it is a number worth moving, and we retest it on you along with the rest of your biomarkers.
Your heart adapts to sustained demand by filling more completely and pushing more blood out with each beat. The textbook name for that amount is stroke volume. A heart with a larger stroke volume moves the same blood in fewer beats, so the resting rate falls.
The largest review of this question pooled 191 studies, and the training that lowered resting heart rate was the training that kept the heart rate elevated for long stretches at a time. Lifting done the ordinary way, with three minutes of standing around between sets, left it about where it started.
Reimers, Knapp & Reimers, Journal of Clinical Medicine 2018 (191 studies, 12,952 participants)
That tells you exactly what the stimulus is. It is sustained elevation. So we put sustained elevation inside the lifting.
The first way we do that is called interval weight training. The set is timed instead of counted. You work for a fixed number of seconds, you rest for the same number of seconds, and you go again.
Work and rest are always the same length here. Twenty seconds on, twenty seconds off. There is a reason for that, and it is a floor reason. Under fatigue a person runs the wrong segment, and it is always the shorter one. Equal segments mean one number on the clock and nothing for you to keep track of while you are breathing hard.
One study ran the same athletes through the same exercises, at the same loads, for the same reps, and changed only the rest between them. With the rest cut down, oxygen use and heart rate rose sharply across the whole session.
Marín-Pagán et al., Biology 2020
Same weights. Same reps. The clock did the conditioning.
The second way is density training. Density is work divided by time. You get a fixed block of minutes, and the job is to do more work inside that block than you did inside it last time.
That means progress does not have to arrive as a heavier weight. It can arrive as the same weight moved more often in the same minutes. Because the block never gets longer, your heart rate stays up while the total work climbs.
Across 37 trials in healthy older adults, resistance training by itself raised peak oxygen uptake, which is the ceiling on what your body can use when it is working hard.
Smart et al., Age and Ageing 2022 (37 studies, 1,641 participants)
There is also a price for bolting a separate endurance session onto a strength program. Across 21 studies, the more endurance work was added on, and the longer and more often it ran, the smaller the gains in muscle, strength and power.
Wilson et al., Journal of Strength and Conditioning Research 2012 (21 studies, 422 effect sizes)
Power, strength and muscle are the three things age takes from you first. We protect them by keeping the conditioning inside the same session.
The last piece happens outside the gym. Ten thousand steps a day. Easy, sustained, no equipment.
In 47,471 adults followed for years, the more steps a person took in a day, the lower their risk of dying, and it fell in a steady line rather than at one magic number.
Paluch et al., Lancet Public Health 2022 (15 cohorts, n=47,471)
That is your easy aerobic work, and you already have room in your day for it. Cardio on top of that is optional and it is yours to enjoy. Your conditioning is already accounted for.
Timed work is where most gyms lose the thread. Once a clock is running, effort drifts, and in an ordinary gym nobody ever finds out which of those reps still counted for something.
The whole gym runs on an AI-based strength measurement system. Artificial intelligence reads exactly what level of effort you are putting in on every single repetition, including the ones inside a timed interval.
The system makes sure you are in the right strength-building and muscle-building zone the entire time the clock is running. No junk reps. That is how one set builds your strength and your conditioning at once, and it is why your resting heart rate comes down while your strength numbers go up. Nobody else can do that, because doing it means reading every repetition while the weight is still in your hands.
Twenty-five minutes. No charge. You walk out with your numbers.
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