Living longer isn’t rare anymore. Muscle mass decides the quality of those years.

Most people plan for their financial retirement more carefully than they plan for their physical one. You already have a sense of how much money you’ll need to be comfortable at 70, living longer than previous generations. But when’s the last time you thought about how strong you’ll be? How mobile? How independent?

Longevity researchers call this the difference between lifespan and health span. Lifespan is how long you live. Health span is how long you live well and are able to move, think, and take care of yourself without assistance. And the average American now spends 12 or more years at the end of life in the gap between the two.

That gap isn’t inevitable. It’s built decades before you feel it. And a small number of specific measures predict how wide it will be.

Muscle mass and bone density are the foundation

If you only paid attention to two things about your body between now and old age, muscle mass and bone density would be the two.

Muscle mass declines about 3 to 8 percent per decade after age 30. After 60, it accelerates. If you’re not actively working to preserve muscle, you’re losing it steadily, quietly, and in ways that don’t feel dramatic until they suddenly do.

Bone density follows a similar trajectory. Bones peak in your 20s and start losing minerals in your 30s. Without regular impact and load, they get less dense every year until fractures become the risk that ends independence for many older adults.

Here’s what makes this so serious: muscle mass and bone density are what let you get up off the floor at 80. They’re what prevent the hip fracture that starts the cascade toward assisted living. They’re what let you carry groceries, garden, travel, and pick up your grandchildren. When they’re gone, most of what defines an independent life goes with them.

The good news is that both are trainable, significantly and at any age. Progressive resistance training (also called strength training or weightlifting) is the single most effective intervention we have for preserving muscle mass and building bone density. Nothing else comes close.

This is not the same as walking or general movement. They matter, but don’t build muscle mass or bone density the way strength training does. Bones and muscles respond to load. If you’re not giving them meaningful load a few times a week, they’re not getting the signal to stay.

Why this matters more urgently for women

Women lose muscle mass faster than men after menopause, when the hormonal shifts that once supported muscle preservation drop off. Women also start with less muscle mass to begin with, which means the losses hit harder.

Osteoporosis affects women at roughly four times the rate of men. One in two women over 50 will experience an osteoporosis-related fracture in her lifetime. That’s not a rare outcome. It’s the most likely outcome for women who don’t actively work to preserve bone density.

Despite this, women have been undertrained for decades. The cultural messaging around women and strength training (that it will make you bulky, that cardio is what women should focus on, that you should be small before you’re strong) has left generations of women without the tools they need to age well.

None of this is inevitable. Strength training a few times a week meaningfully slows muscle loss, preserves bone density, and reduces fracture risk. It also supports metabolic health, mood regulation, and sleep quality.

One example worth mentioning: strength training before, during, and after pregnancy is now recognized as one of the most protective things a woman can do for delivery, recovery, and long-term pelvic floor health. Building strong muscles and bones before pregnancy makes the physical demands of carrying, delivering, and recovering from a baby significantly easier. The same is true for menopause, another major physical transition where a strong body handles the shift better than a weak one.

The through-line is simple: strong bodies handle stressors better. Pregnancy is a stressor. Menopause is a stressor. Aging is a stressor. Strength is what makes each one survivable and, often, transformative.

Grip strength: a surprising longevity signal

Grip strength has emerged as one of the most reliable predictors of longevity in the research. Not because grip is uniquely important on its own, but because it’s a proxy for overall muscular health.

People with stronger grip strength have lower rates of cardiovascular disease, better cognitive function into old age, and lower all-cause mortality. Weak grip is associated with faster decline across almost every system in the body.

The good news is that you don’t need to train grip specifically. Regular strength training, including deadlifts, pulling exercises, and carrying heavy things, builds grip strength as a byproduct. If you’re strength training consistently, you’re building the metric that predicts how well you’ll age.

VO2 max: what your cardiovascular system is telling you

VO2 max measures how efficiently your body uses oxygen during exercise. It’s the single strongest predictor of cardiovascular fitness, and one of the strongest predictors of longevity overall.

VO2 max declines about 10 percent per decade after 30 without training. That decline is one of the primary reasons older adults tire faster, recover more slowly, and become less mobile over time.

Cardiovascular exercise, including running, cycling, and high-intensity intervals, is the most direct way to improve VO2 max. But there’s a second intervention that has emerged in recent research as almost equally effective: regular sauna use.

Multiple studies have shown that consistent sauna sessions produce cardiovascular adaptations similar to moderate cardio exercise. Heart rate rises, blood vessels dilate, plasma volume increases. Over time, this translates to improved VO2 max, lower resting blood pressure, and reduced cardiovascular mortality.

For people who can’t do intense cardio due to injury, age, or preference, sauna offers a real alternative. And for people who already do cardio, sauna stacks with training rather than replacing it. You get both cardiovascular and heat-adaptation benefits.

The point isn’t that sauna replaces exercise. It’s that the interventions that meaningfully extend health span aren’t limited to what you do at the gym. Recovery and heat exposure are trainable inputs too.

What consistent work actually gives back

Muscle mass, bone density, grip strength, and VO2 max are not vanity metrics. They are the specific measures that determine whether you’ll be walking your daughter down the aisle at 65, hiking with your grandkids at 75, and living independently at 85.

Every one of them is trainable. Every one of them responds to consistent, non-negotiable practice. And every one of them declines without that practice, whether you’re paying attention or not.

At Release, we’ve built our space around this exact idea. Strength training and cardio classes to build the muscle mass, bone density, and cardiovascular capacity that predict how well you age. Bliss for the recovery and heat exposure that support long-term health. Massage and facials for the tension release and skin maintenance that keep the whole system running.

None of it is about looking younger or feeling relaxed for an afternoon. It’s about being in a body that works for the next 30 years the way you want it to.

The gap between lifespan and health span is real. But it isn’t fixed. It’s being written right now, in the practices you’re keeping or skipping this month.