Why Our Muscles Weaken With Age (and How to Keep Them Strong)

Worried about losing your hard-earned gym gains later in life? Well, later life muscle loss – also known as sarcopenia – happens to us all. Luckily, we’ve got some advice that could help.

Ever wondered why workouts feel more like an Everest ascent as the years go on? In your early 20s, you might have conquered back-to-back workouts and barely felt an ache or pain the next day. These days though, you’re more likely to grapple with instant fatigue and longer recovery periods after an intense gym sesh. 

Along with grey hairs and two-day hangovers, loss of muscle mass is considered one of those inevitable parts of the ageing process. But why exactly does it happen and, more importantly, what can we do to slow down its progression?

To help us understand the basic biomechanics, we spoke to an exercise physiologist to find out more about the science of age-related muscle loss through the decades. Whether you’re keen to stay in peak shape later in life or you’re simply curious about what’s happening in the body, we’ve got you covered.

What happens to our muscle mass through the decades?

As we age, our bodies go through natural physiological changes. In our 20s, we’re generally considered to be at the top of our game, hence why most pro athletes sit in this age bracket. "When you’re younger, your muscles respond very quickly to resistance and exercise, which leads to faster muscle growth and quicker results," explains clinical exercise physiologist Karen Owoc. A University of Toronto study even pinpointed the specific age that your muscles naturally hit their peak: 25 years old.

You’ve probably heard the rather depressing saying that once you hit your late 30s, everything ‘starts to go downhill’. That's not quite true, but as Owoc explains, "Just like any other body part, the muscle fibres age and start to shrink in size and number as we age.” 

Studies have shown that from the age of 30, you roughly lose about 3 to 8% of your muscle mass per decade as a part of the natural ageing process.

By the time you hit your 40s, changes in muscle mass become even more noticeable and those once firm and defined muscles can start to lack their previous fullness and shape. A 2005 scientific review paper found that even if you stick to a healthy diet and stay roughly the same weight during this decade, without the right exercise and nutrition strategy, you’ll still spot sneaky changes in the mirror. This is because we all experience a natural increase in fat mass and a decrease in muscle mass as the years go on.

When we hit mid-life, this process accelerates. “From your 50s onwards, muscle loss increases to around 5 to 10% every decade,” says Owoc. “So by the time you’re 65, you’ve probably lost around 15 pounds of muscle in total.” 

Of course, sarcopenia – the scientific term for muscle loss as we age – is generally nothing to panic about, but it can stop us from going about our day-to-day business pain-free. As Owoc explains: “Once a fair amount of muscle mass is lost in later years, people tend to have less functional strength, balance, endurance and mobility, which increases the risk of falls and injuries.”

Why do we lose strength and muscle mass? Sarcopenia explained

Sarcopenia happens for a number of different reasons, including biological, lifestyle, and hormonal changes. In our 20s, Owoc says we benefit from a “faster metabolism” and higher levels of anabolic hormones naturally produced by our bods, including testosterone, growth hormone, and insulin-like growth factor 1. These hormones play a pretty vital role in fueling muscle growth and repair, supercharging our body's ability to adapt and thrive. 

It makes sense then, that as their levels naturally dip with age, the body's ability to build and maintain muscle mass gets compromised. “Couple this with the fact that there’s a gradual decline in muscle tissue, both in the number and size of muscle fibres from the age of 30 onwards, and it’s no surprise that people start to freak out about changes to their body,” says Owoc. 

But it’s not just the number of candles on your birthday cake that might be sabotaging your gym gains. A scientific review published in 2004 concluded that our lifestyle choices can play a major role too. “People are generally more sedentary during their 30s, 40s and beyond, as they’re working and commuting long hours with less time for movement, recovery and good nutrition,” Owoc believes. This is especially true in our current WFH culture.

Owoc also points to a lack of protein as a potential factor. “We know that protein is essential for muscle growth and repair, especially as we get older, but lots of people fuel insufficiently in this area, so they don’t have the nutrients they need for proper muscle maintenance and regeneration.”

Plus, women in particular face specific challenges in maintaining muscle mass as they age, because of perimenopause - which starts in the mid-40s (with the oft-cited average age being 47.5), but can begin as early as the mid-30s or as late as the mid-50s. “The reproductive hormone oestrogen plays a huge role in maintaining muscle mass and strength in women. During the run-up to that final period though, it’s in gradual decline,” says Owoc. As it comes with a whole host of other unfun symptoms like fatigue, insomnia, and mood changes, it can have a two-fold effect on your muscles, killing your motivation to stick to a regular gym schedule. 

3 tips for retaining muscle mass as you age

Prioritise progressive strength training

If you want to keep (or grow) your muscle mass and speed your metabolic rate up at the same time, Owoc says that you need to think about switching from cardio to strength and resistance training. “Lifting weights engages your muscles by placing a load against them. This activates your muscle fibres and stimulates their growth,” she explains. “When you challenge your muscles through resistance exercises, you create tiny microscopic tears to the muscle fibres, causing them to become stronger and larger during the recovery process.”

The key thing here is to up your weight over time, so your results don’t plateau. “If you can do three sets of eight to 12 reps fairly comfortably, then it's time to increase your weights,” Owoc says.

Make sure you’re getting enough protein

Diet culture has duped us into thinking that to be fit and healthy, we need to consume fewer calories. But this overlooks one simple fact: we need quality protein to maintain the muscle mass we already have.

"How much protein do I need?" Well, older adults should aim for at least 1g protein per kg of body weight compared to the RDA of 0.75g protein per kg of body weight. 

There are two different types of protein: complete and incomplete. Complete proteins contain all nine essential amino acids, whereas incomplete proteins are missing one or more. Animal proteins including meat, poultry, fish, eggs and dairy are good sources of complete protein, but Owoc prefers plant-based options, which include quinoa, buckwheat and hemp seed.

Protein shakes can also keep you topped up. “You don’t metabolise protein as quickly as you did when you were younger, so I’d recommend eating a good source of protein with every meal,” Owoc adds.

Recover well

It’s all well and good bench pressing a PB in the gym, but without adequate rest and recovery, you won’t reap those muscle-building rewards. “During recovery, the body repairs the damage made to the muscle fibres during exercise,” notes Owoc. “It’s this process that causes our muscles to get stronger and bigger - effectively building mass as we go.”

Recovery generally involves resting from intense exercise, but you can throw in gentle activities like stretching, foam rolling, massage and swimming on your rest days too.

“What you do outside of the gym is just as important as what you do inside it,” stresses Owoc, “so allow yourself days to rest, sleep and recover.”