Age-Related Muscle Loss

What sarcopenia is

Sarcopenia is not a softer word for getting older. It is a diagnosis, with its own tests and its own thresholds. The European Working Group on Sarcopenia in Older People, whose 2019 consensus is the reference clinicians work from, defines it plainly:

“Sarcopenia is a progressive and generalised skeletal muscle disorder that is associated with increased likelihood of adverse outcomes including falls, fractures, physical disability and mortality.” [EWGSOP2, 2019]

The 2019 update changed what counts as the main sign of it. Earlier versions looked mainly at muscle size. The current version puts strength first, because strength predicts falls, disability and death better than size does, and confirms the diagnosis with muscle quantity second [EWGSOP2, 2019]. That single change matters for how the test in the next section works: it starts with what you can do, not with a scan.

Size and strength do not move together, and mixing them up hides the real problem. In the studies that measured both in the same people, strength was lost two to five times faster than muscle size [Mitchell et al., 2012]. The size loss itself is slow: pooling the studies that measured it, the median rate is 0.47% of muscle mass a year in men and 0.37% a year in women [Mitchell et al., 2012]. Half a percent a year is invisible in a mirror. It is the strength underneath it that goes first, and that is what a test can catch years before the mirror would.

What sarcopenia costs, in the outcomes that have actually been measured rather than the ones people assume, is specific rather than vague. A systematic review pooling studies that used the same definition found a pooled odds ratio for mortality of 3.6 among people with sarcopenia, and a pooled odds ratio of 3.0 for functional decline [Beaudart et al., 2017]. The EWGSOP2 consensus adds a cost figure: among older adults admitted to hospital, those with sarcopenia on admission were more than 5-fold more likely to have higher hospital costs than those without it [EWGSOP2, 2019].

Two outcomes are weaker than their reputation. Falls and fractures are widely assumed to be sarcopenia's headline risk, and the picture there is thinner than mortality's. Both studies that looked at falls found a significant link, but there were only two of them, too few to pool [Beaudart et al., 2017]. Fractures were more common in people with sarcopenia only when they also had low bone mineral density, not in people with sarcopenia and normal bone density [Beaudart et al., 2017]. The two conditions compound each other rather than acting alone, which is also why our guide to bone density and osteoporosis and this one keep pointing at each other.

Sarcopenia is common enough to matter locally, even without a national figure to quote. A Massey University study of 91 residents across three Auckland aged-care facilities found 41% were sarcopenic [Massey University, 2022]. That is one study of three facilities, not a national rate, and we state it as exactly that. It is still the only New Zealand-specific number either way.

How it's measured

EWGSOP2 sets out a four-step pathway for diagnosis, and it is worth knowing the shape of it even outside a clinic, because two of its four steps are things a coach can measure too. The steps are Find, Assess, Confirm and Severity [EWGSOP2, 2019]. A questionnaire or clinical suspicion finds who might have it. Grip strength or a chair stand assesses whether strength is actually low. A DXA or bioimpedance scan confirms low muscle quantity. A walking speed test grades how severe it has become.

Grip strength

Grip is measured with a handheld dynamometer, squeezed as hard as possible. EWGSOP2's cut-off points for low strength are under 27kg for men and under 16kg for women [EWGSOP2, 2019]. Grip is not tested because hand strength matters on its own. It is tested because it is quick, cheap, and correlates moderately with strength elsewhere in the body:

“Grip strength correlates moderately with strength in other body compartments, so it serves as a reliable surrogate for more complicated measures of arm and leg strength.” [EWGSOP2, 2019]

Sit-to-stand (chair stand)

The chair stand test is a proxy for leg strength. EWGSOP2 describes it plainly:

“The chair stand test measures the amount of time needed for a patient to rise five times from a seated position without using his or her arms; the timed chair stand test is a variation that counts how many times a patient can rise and sit in the chair over a 30-second interval.” [EWGSOP2, 2019]

Taking longer than 15 seconds to complete five rises is the cut-off for low strength, for both men and women [EWGSOP2, 2019]. A slower version, walking speed measured over four metres, is used separately to grade how severe the condition is once it is confirmed: 0.8 metres a second or slower is EWGSOP2's cut-off for severe sarcopenia [EWGSOP2, 2019].

What the free strength test does and does not tell you

Our free strength test at the studio uses two of these: grip and sit-to-stand. It gives you real numbers on both, and it sets the starting loads for your first session from them. It does not confirm low muscle quantity, which needs a DXA or bioimpedance scan, and it does not produce a diagnosis. What it produces is a measurement, which is exactly what it is for: knowing where you actually stand, rather than guessing.

How fast it reverses

Muscle strength responds faster than most people expect, including in people who have never trained before. In a study of older adults with no previous resistance training, both arm and leg strength had improved measurably after four weeks, and kept improving in every four-week block through to the end of the sixteen-week programme [Coetsee, 2015]. Across the full sixteen weeks, arm strength rose 39% and leg strength 167% [Coetsee, 2015]. Both averages carry a wide spread, and a leg that has never been loaded has the most room to move, which is why that figure is so large. The direction is the part to take away: people starting from nothing got stronger, and went on getting stronger for as long as the researchers kept measuring.

That study measured strength in older adults generally, not people already diagnosed with sarcopenia specifically, and it is the same study our guide to strength training over 60 draws on for the same number. We are using it here for the same reason: it is the clearest evidence available for how quickly untrained older muscle responds to load, and there is no reason to expect sarcopenic muscle to be slower to start responding, only slower to reach the same load.

What this does not tell you is whether a scan would show your muscle quantity back in the normal range, or whether your grip or sit-to-stand time has cleared EWGSOP2's cut-off points. Strength gains and a change in diagnosis are not the same event, and only a repeat assessment against those cut-offs answers the second question. What four weeks reliably gives you is a stronger grip and an easier stand than you had a month before, measurable on the same test that started you.