Why Muscle Strength Is the #1 Predictor of Healthy Aging

There’s one metric that consistently predicts how well we age, and it’s finally showing up in the conversations that matter. It’s not blood pressure, cholesterol, or BMI. It’s muscle strength.

Muscle health plays a central role in healthy aging, influencing mobility, quality of life, and metabolic health. Yet historically, strength has been viewed primarily through the lens of fitness or performance rather than as a core clinical target.

Today, the evidence is clear: healthcare providers should be paying far more attention to muscle health. But until recently, we’ve lacked simple, evidence-based guidelines and practical tools to translate this into actionable guidance for our patients.

Now that’s starting to change.

For the first time since 2009, the American College of Sports Medicine has updated its guidelines on resistance training. The new Position Stand, led by Dr. Brad Currier, PhD, a member of the Research and Development team at Timeline (the company behind Mitopure®), reflects a major step forward in how we understand and prescribe strength training.

Beyond the new guidelines, clinically validated compounds like Urolithin A are expanding our ability to support muscle health. Together, these advances mean practitioners are better equipped to target this critical marker of healthy aging.

 

A Long Overdue Update to the ACSM Strength Training Guidelines

It’s been more than 15 years since the ACSM resistance training guidelines were last updated. Since then, there has been an explosion of research in the area, with more than 30,000 new publications.

Historically, prescribing resistance training meant navigating a complex set of variables, often captured in the FITT-VP framework (frequency, intensity, time, type, volume, progression). While thorough, this level of detail has made it difficult for both providers and patients to implement consistently in real-world settings.

Now, drawing from more than 130 systematic reviews and over 30,000 participants, the new ACSM position paper offers clearer, practical guidance to help us confidently prescribe strength training in clinical practice.

 

ACSM Guidelines: How to Train for Strength, Muscle, and Power

Here’s an overview of the ACSM recommendations to target key components of muscle health:

 

Muscle Strength

Muscle strength refers to the ability of the muscle to generate force. Research suggests that this may be a stronger indicator of mobility, independence, and all-cause mortality than muscle size alone.

The new guidelines reinforce that resistance training is key to maintaining and improving muscle strength. Free weights, machines, resistance bands, and bodyweight exercises can all be effective. Strength improves with most types of resistance training, but higher loads, full-range of motion, and training at least twice per week are most effective.

 

Hypertrophy

Muscle mass is another important parameter of muscle health, declining at rates of up to 3-8% per decade after age 30, and accelerating after age 60.

As with strength, building muscle mass does not require a gym membership or complex protocol. Hypertrophy can be achieved by using higher volumes (over 10 sets per muscle group per week) and by focusing on the lowering part of the movement (eccentric overload). This matters more than training to absolute failure, time under tension, complex protocols, or advanced tools like blood flow restriction.

 

Power

Muscle power, or the muscle’s ability to generate force quickly, declines earlier and more quickly than muscle strength. It’s an essential component of everyday movements such as climbing the stairs or getting up from a chair.

Power is best developed with moderate loads, emphasizing quick concentric contractions and maintaining control during the eccentric phase. Olympic lifts and power training can also effectively enhance muscle power.

Since muscle power declines with age, this represents an important but often overlooked target for preserving functional independence.

 

Muscle, Mitochondria, and Urolithin A

Muscle quality decline is more than just about the number of sessions in the gym. Supporting mitochondrial health, particularly through mitophagy (the recycling of mitochondria), is emerging as an important strategy to support muscle health as we age.

One evidence-based strategy to naturally support mitophagy and improve mitochondrial function is the postbiotic compound Urolithin A. It’s produced by the microbial action on the foods that contain the UA precursor compounds, ellagitannins, and ellagic acid (found in pomegranates, berries, and some nuts). However, only 1 in 3 people house the correct microbiome to make Urolithin A.

Research shows that Urolithin A has the ability to trigger mitophagy and, by promoting the removal of damaged mitochondria, it ensures that our cells remain vibrant, energetic, and function at their optimal levels. This cellular rejuvenation, as seen in clinical trials, translates to tangible health benefits, like improved muscle function.

Mitopure, a clinically validated form of Urolithin A, has been used in clinical research at a dose of 1000 mg with demonstrated effects on cellular and muscle health,* including:

• Improved markers of mitochondrial health, including mitophagy, in skeletal muscle after one month ^a
• Improved muscle strength by 10% in four months in sedentary middle-aged adults ^b
• Improved muscle endurance by 17% in two months in sedentary older adults ^c

Importantly, these improvements occurred without changes to diet or exercise. Given that nearly 80% of U.S. adults do not meet strength-training guidelines, supplementing with a high-strength Urolithin A product such as Mitopure may offer a practical way to achieve meaningful improvements in muscle health.

 

Urolithin A for Athletes

Beyond its role for aging muscle, Urolithin A in the form of Mitopure has been clinically studied in younger athletic populations and offers benefits for performance and recovery.

Data from human trials show that supplementing with 1000 mg of Urolithin A (Mitopure) for 4-6 weeks can:

• Support endurance capacity during intense training ^d
• Protect from oxidative stress during intense training ^d
• Improve rates of perceived exertion (RPE) after a 3000m time trial in professionally trained athletes compared to a placebo group ^e

While supporting mitochondrial health is one important piece of the puzzle, it doesn’t replace the foundational role of resistance training. This is where the updated ACSM guidelines provide critical direction for clinical practice.

 

Muscle Health as Medicine: Practical Strength Training for Longevity

The overall takeaway from this new Position Stand is that many forms of strength training are effective. Home-based workouts with resistance bands can deliver results comparable to those who go to the gym and use machines and free weights.

For providers, this shifts the focus to helping patients find a workout that fits their lifestyle and increases the likelihood of long-term adherence.

Muscle health should be a core focus for any longevity or functional medicine practitioner. With the updated ACSM Position Stand and tools like Mitopure, clinicians are now better equipped than ever to make evidence-informed recommendations that support long-term health.

For healthcare practitioners interested in learning more about Mitopure and how to incorporate it into clinical practice, visit Pro.Timeline.com.

 

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

References

a) 1000mg Mitopure has been shown to induce gene expression related to mitochondrial function and metabolism.

b) Clinical studies find improvements in muscle strength at 1000 mg and 500 mg dosages by 10-12%, respectively. Clinical studies consistently find improvements in muscle strength and endurance in a varied subset of the population ranging from resistance-trained athletes in their 20s to middle-aged adults with an average BMI of 29.52.

c) Our clinical studies showed that sedentary adults aged 65–90 improved muscle endurance, measured as leg and hand repetitions to fatigue, after daily supplementation with 1,000 mg Mitopure®.

d) The clinical study showed that daily supplementation with 1,000 mg Mitopure® for 6 weeks supported recovery during intense preseason training in academy‑level soccer players.

e) Our clinical study showed that trained runners reported lower rate of perceived exertion (RPE) after 4 weeks of daily supplementation with 1,000 mg Mitopure®, compared with placebo.