# Strength, Power & Movement

Building Capacity to Keep Doing What Matters

![Mother climbing stairs while holding groceries and a child](https://cdn.sanity.io/images/7yi5boyj/production/f3d31530352f1c24ca5c0a3d6d05631888f3a161-1254x1254.png?w=1600&fm=webp&q=80&auto=format)

## **Strength, Power & Movement: Building the Capacity to Keep Doing What Matters**

Most people do not think about strength when they stand up from a chair, carry a suitcase, climb a flight of stairs, lift a child, get up from the floor, or catch themselves after a misstep. They simply do it. That changes when the physical capacity required to perform a task begins approaching the maximum capacity available to perform it.

Strength and power generally reach their highest levels in early adulthood and decline thereafter. The trajectory varies considerably between individuals and is influenced by genetics, health, activity, training, injury, nutrition, and other factors. But the direction is predictable: without an adequate training stimulus, physical reserve tends to diminish with age.

Initially, that decline may be almost invisible. You can still climb the stairs, carry the groceries, or spend the day skiing. The task simply consumes a slightly greater percentage of your available capacity. Eventually, however, the gap between what your body can do and what life requires it to do becomes smaller.

This is why strength and power matter well before someone becomes frail. The objective is not simply to become stronger for the sake of lifting heavier weights. It is to preserve enough strength, power, and movement capacity that the activities you want to perform remain comfortably below the limits of what your body can do.

## **Muscle mass matters—but it is not the same thing as strength**

Skeletal muscle is important for far more than appearance. It contributes to movement, glucose disposal, metabolic health, bone loading, physical resilience, and recovery from illness or injury. Maintaining adequate muscle therefore becomes increasingly important as we age.

But muscle mass and muscle function are not interchangeable. Muscle mass describes how much muscle tissue we have. Strength describes how much force we can generate. And the two do not decline at the same rate. Goodpaster and colleagues demonstrated this in the Health, Aging and Body Composition Study. They followed 1,880 older adults for three years while measuring leg lean mass and knee-extensor strength. Leg lean mass declined by approximately 1% per year, while strength declined approximately three times faster—roughly 2.6–4.1% per year depending on sex and race. Perhaps more importantly, participants who maintained or even gained lean mass did not necessarily maintain their strength.¹

That tells us something important about aging. The amount of muscle matters. But what that muscle can do matters even more. Age-related changes in neuromuscular activation, motor units, muscle architecture, contractile properties, fat infiltration, and other aspects of muscle quality can impair function in ways that cannot be captured by measuring muscle quantity alone. This is one reason body composition and physical-performance testing answer different questions. A DEXA or BIA measurement can tell us something about the tissue you have but it cannot tell us how effectively you can use it.

## **Strength is physical reserve**

Consider two people who each need to generate the equivalent of 30 units of force to perform a particular task. If one person's maximum capacity is 100, that task requires only 30% of their available strength. If another person's maximum capacity is 40, exactly the same task requires 75%. The task has not changed, the reserve has. This is similar to the concept of physiological reserve in cardiorespiratory fitness. When reserve is large, ordinary activities remain comfortably below maximal capacity. As reserve narrows, those same activities consume a progressively greater percentage of what is available. Eventually, the margin becomes small enough that a previously ordinary task becomes difficult or impossible. This is how strength becomes a question of independence rather than simply athletic performance.

## **Strength predicts more than performance in the gym**

Muscular strength is associated with physical function, disability, frailty, and survival.² Grip strength has been particularly well studied because it is inexpensive, reproducible, and easy to measure. It does not represent every aspect of whole-body strength, but it can provide useful information about overall neuromuscular capacity.

A 2024 study by Andersen and colleagues provides an interesting example at the extreme end of aging. The investigators studied 1,890 adults aged 90 years and older from 27 European countries and Israel for approximately four years. While they didn’t find a specific threshold of grip strength that resulted in increased mortality, overall, there was an inverse relationship between grip strength and mortality. Compared with a reference grip strength of 18 kg, 10 kg was associated with approximately a 27% higher relative mortality hazard, while 31 kg was associated with approximately a 31% lower hazard.³

Strength reflects many aspects of health simultaneously: muscle function, neurological integrity, habitual physical activity, nutritional status, disease burden, and overall physiological reserve. But that may be precisely why it is useful. Strength is a marker of physical capacity, not merely an athletic characteristic.

## **Power adds something strength alone cannot measure**

Strength answers how much force you can generate. Power answers how quickly you can generate it. In mechanical terms, power incorporates both force and velocity. That distinction becomes increasingly important with age because many of life's physical demands do not give us unlimited time to generate force. Catching yourself when you trip requires rapid force production. So does recovering your balance, stepping quickly onto a curb, accelerating up a staircase, moving out of the way of an obstacle, or reacting to something unexpected. A person may possess enough maximal strength to perform a movement slowly but not generate that force quickly when the situation demands it. Power also appears to decline earlier and more rapidly with age than maximal strength, and it may be particularly relevant to physical function in older adults.⁴ This is why strength and power should not be treated as interchangeable. Strength determines how much force is available. Power determines how quickly you can access it.

## **Power may also tell us something about long-term health**

A recent prospective study by Araújo and colleagues provides an intriguing illustration of this distinction. Investigators followed 3,889 adults aged 46–75 years for a median of 10.8 years and compared relative muscle strength and relative muscle power with subsequent mortality.⁵ While the study was observational and had wide confidence intervals, the differences associated with power were striking. Compared with participants in the highest quartile, men in the lowest relative-power quartile had an adjusted mortality hazard ratio of 5.88. For women, the corresponding hazard ratio was 6.90. Associations for low relative strength were considerably smaller: 1.62 in men and 1.71 in women.⁵

We cannot conclude from this study that increasing muscle power will reduce someone's mortality risk sixfold. But the findings support a broader concept: the ability to generate force quickly may capture an important dimension of physiological reserve that strength alone does not. That matters because power loss occurs faster than both strength and muscle mass, is relevant for life, and while trainable, requires dedicated attention to maintain. A systematic review and meta-analysis of 20 randomized trials involving 566 community-dwelling older adults found that power-oriented resistance training produced a modest improvement in physical function compared with traditional resistance training, although the certainty of the evidence was low.⁶

Power training does not have to mean Olympic lifting, maximal jumping, or other high-risk exercises. The stimulus can be scaled to the individual. Rapid sit-to-stands, medicine-ball throws, appropriately selected jumps, or resistance exercises performed with the intent to accelerate the load can all train aspects of power. The appropriate exercise depends on the person's starting capacity.

## **Movement is where strength and power become useful**

Strength and power do not exist in isolation. They have to be expressed through movement. Adequate joint mobility allows the body to access useful positions. Balance helps control the center of mass over the base of support. Coordination allows force to be applied in the appropriate direction and sequence. Strength creates force. Power allows that force to be generated rapidly. Together, these determine what we can actually do.

Movement assessment can identify limitations that may not be apparent from body composition or isolated strength testing. Restricted range of motion, poor control of a particular movement, substantial side-to-side differences, pain with loading, or difficulty tolerating a particular task may identify areas that deserve additional attention. However, human movement is not perfectly symmetrical, and asymmetry by itself does not necessarily represent dysfunction or predict injury. The scientific literature on movement-screening tools illustrates this limitation. Studies examining whether movement quality or composite screening scores predict subsequent injury have produced inconsistent results, and systematic reviews have found important differences by population, sport, age, and methodology. Screening measures generally do not provide sufficient information to classify an individual's future injury risk with confidence.⁷˒⁸

That does not make movement assessment useless. It changes the question. Rather than asking whether every asymmetry should be "corrected," we can ask whether a particular finding is meaningful for the individual. This keeps movement assessment from becoming an exercise in finding imperfections in otherwise healthy people.

## **Staying capable also means staying available**

Building physical capacity is only useful if you can continue using it. Musculoskeletal injury can interrupt training for weeks or months. During that time, strength, cardiorespiratory fitness, skill, and confidence can decline. More significant injuries can interfere with work, recreation, sleep, travel, and ordinary activities of daily living. Some people never completely return to their previous level of function.

As physiological reserve decreases with age, those interruptions can become increasingly consequential. This makes injury mitigation part of a long-term health strategy. The objective is not to eliminate injury risk. No screening test, movement pattern, exercise program, or training technique can guarantee that. Instead, the goal is to increase the body's capacity to tolerate the demands placed upon it. That means developing strength through useful ranges of motion, exposing tissues progressively to appropriate loads, allowing adequate recovery, addressing pain or meaningful functional limitations when they arise, and preparing specifically for the activities the body will be asked to perform. A person who wants to ski at 70 needs more than adequate muscle mass. Skiing requires lower-body strength and power, balance, eccentric control, mobility, cardiorespiratory fitness, and the ability to repeatedly tolerate substantial forces. Someone who wants to play tennis at 75 needs a somewhat different combination: acceleration, deceleration, lateral movement, rotational power, coordination, and sufficient tissue capacity to tolerate repeated loading. The activity defines the demand. Training builds the capacity to meet it.

This is also why training should progress rather than simply repeat. As the body adapts, the stimulus must eventually change if additional adaptation is desired. The specific form of progression depends on the goal and may involve resistance, repetitions, movement velocity, range of motion, complexity, volume, or other variables. The basic principle is straightforward: expose the body to an appropriate challenge, allow it to adapt, and gradually increase what it can tolerate.

## **Independence matters—but it is a low bar**

Avoiding frailty matters. Being able to get out of a chair, walk independently, carry groceries, and get off the floor matters. But for someone in their 40s or 50s, simply preserving the minimum physical capacity required for independent living is an unnecessarily modest objective. You may want to hike at 70. Ski at 65. Play tennis at 75. Carry your own luggage through an airport. Spend a day working in the garden. Get down on the floor with your grandchildren (and get back up). Travel somewhere where stairs are unavoidable. Help someone else rather than needing someone else to help you. The physical demands of those activities are considerably higher than the minimum requirements for independent living. That changes the question to: "How much physical reserve do I want to carry into later life?"

## **Build reserve before you need it**

The exact age at which strength or power peaks is less important than the overall trajectory. Physical capacity is generally highest earlier in adulthood. Without continued training, it tends to decline. At first, that decline may have almost no effect on daily life because there is substantial reserve. The consequences become apparent when the reserve begins to run out. That makes strength and power somewhat analogous to retirement savings. You would not ideally begin saving for retirement on the day you stop working. Similarly, the ideal time to begin preserving physical capacity is not when getting out of a chair has already become difficult. Build capacity while building capacity is still relatively easy. Preserve it before losing it becomes consequential.

Importantly, this does not mean that someone who starts later has missed the opportunity. Older adults remain highly responsive to resistance training. Meta-analytic evidence demonstrates improvements in strength, physical function, and other health-related outcomes in adults over 60.⁹ Power can also improve with appropriately designed training, and power-oriented training may provide additional functional benefits in some older adults.⁶˒¹⁰ The physiology remains adaptable. Starting earlier simply gives us more reserve to work with.

## **Strength and power require specific training**

Walking, running, cycling, swimming, yoga, Pilates, and recreational sports can all contribute to health and physical function. But being physically active is not necessarily the same thing as providing the body with the stimulus required to preserve maximal strength and power. Strength requires resistance and the body must regularly encounter loads substantial enough to require meaningful force production. Power requires intent to move quickly. Resistance training provides the force-producing foundation while power-oriented training teaches the body to express that force rapidly. Balance, mobility, coordination, and task-specific movement make that capacity useful.

## **Measure what you want to preserve**

Body composition tells us something about how much lean tissue a person has. It does not tell us how strong that tissue is. Strength testing tells us how much force someone can generate. It does not necessarily tell us how rapidly they can generate it. A power assessment adds another dimension. And none of those measurements alone tells us whether someone can move effectively through the tasks that matter to them. This is why physical assessment should include measures of function, not simply mass.

Depending on the individual, useful measurements might include grip strength, lower-body strength, jumping or other power assessments, balance, mobility, movement quality, and task-specific performance. No single test captures the entire system and the objective is not to accumulate scores. The purpose of measurement is to identify whether someone has sufficient capacity for the life they want to lead, determine where meaningful limitations exist, guide training, and evaluate whether that training is producing the intended adaptation.

## **The goal is capacity**

Muscle mass, strength, power, balance, mobility, and movement matter. But none of them is ultimately the goal. The goal is what they allow you to do. We cannot prevent every age-related change, illness, or injury. Physical capacity will eventually decline. But neither the starting point nor the trajectory is entirely predetermined. Muscle can be built, strength and power can be trained, movement can be practiced, and physical reserve can be accumulated before its absence becomes obvious.

The objective is not simply to preserve enough function to remain independent. It is to build enough capacity today, and preserve enough of it over time, that the physical demands of the life you want to live remain comfortably below the limits of what your body can do.

## **References**

1. Goodpaster BH, Park SW, Harris TB, et al. The loss of skeletal muscle strength, mass, and quality in older adults: the Health, Aging and Body Composition Study. _J Gerontol A Biol Sci Med Sci._ 2006;61(10):1059-1064.
2. Cruz-Jentoft AJ, Bahat G, Bauer J, et al. Sarcopenia: revised European consensus on definition and diagnosis. _Age Ageing._ 2019;48(1):16-31.
3. Andersen AL, et al. Association of muscle strength with all-cause mortality in the oldest old: prospective cohort study from 28 countries. _J Cachexia Sarcopenia Muscle._ 2024.
4. Reid KF, Fielding RA. Skeletal muscle power: a critical determinant of physical functioning in older adults. _Exerc Sport Sci Rev._ 2012;40(1):4-12.
5. Araújo CGS, Kunutsor SK, Eijsvogels TMH, et al. Muscle power versus strength as a predictor of mortality in middle-aged and older men and women. _Mayo Clin Proc._ 2025;100(8):1319-1331.
6. Balachandran AT, Steele J, Angielczyk D, et al. Comparison of power training vs traditional strength training on physical function in older adults: a systematic review and meta-analysis. _JAMA Netw Open._ 2022;5(5):e2211623.
7. Moore E, et al. Factors Influencing the Relationship Between the Functional Movement Screen and Injury Risk in Sporting Populations: A Systematic Review and Meta-analysis. _Sports Med_. 2019; 49(9): 1449-1463.
8. Dorrel BS, et al. Evaluation of the Functional Movement Screen as a Prediction Tool Among Active Adult Populations: A Systematic Review and Meta-analysis. _Sports Health_. 2015; 7(6): 532-7.
9. Kashi SK, Mirzazadeh ZS, Saatchian V. A systematic review and meta-analysis of resistance training on quality of life, depression, muscle strength, and functional exercise capacity in older adults aged 60 years or more. _Biol Res Nurs._ 2023;25(1):88-106.
10. Kite C, Lagojda L, Laddu D, et al. High-velocity power training has similar effects to traditional resistance training for functional performance in older adults: a systematic review. _J Physiother._ 2023;69(3):148-159.