WHY POWER OUTPUT DECLINES FASTER THAN STRENGTH AFTER 50 — AND HOW TO STOP IT
From The Functional Fitness Protocol — Chapter 7
By Will Power · Marine veteran, four-time Ironman, 300+ races · Last updated July 8, 2026
Not a physician, dietitian, researcher, healthcare provider, lawyer, or financial advisor. How studies are selected and cited
ANSWER
Endurance training develops sustained aerobic output, not power, the rate of force development. In studies of older adults, power declined faster than strength. Here is what the research measured and how Hyrox, CrossFit, and HIIT train it.
There are two separate things your muscles do, and endurance training trains only one of them.
The first is sustained aerobic output — the ability to maintain moderate force production over hours. This is what triathlon, marathon running, and cycling develop. You get good at it. After fifteen years of training, you can sustain effort at threshold pace for longer than most people half your age, and your slow-twitch fiber density reflects that investment.
The second is power — the ability to produce force quickly. Not just strength, but rate of force development: how fast you can go from relaxed to fully contracted. This is what a sled push, a box jump, a sandbag clean, or a 100-meter sprint requires. And it is the quality that endurance training on its own does little to develop, because the training never asks for it.
The problem is that, in studies of older adults, power has declined faster than strength.
What the Research Shows
Skelton DA et al. (1994) measured strength and power in 100 healthy adults aged 65–89. This was a cross-sectional study, comparing people of different ages rather than following the same people over time. Across that age range, the differences in isometric strength were equivalent to losses of 1–2% per year, and the differences in leg extensor power to roughly 3.5% per year. Power declined faster than knee extensor strength in the men; in the women the difference was not statistically significant.
The mechanism is fiber type. Aging is associated with the loss of type II muscle fibers, the fast-twitch fibers responsible for explosive output. Tøien et al. (2023) took muscle biopsies from men over 70 who had trained for strength their whole lives, men who had trained for endurance their whole lives, and recreationally active men of the same age. The lifelong strength trainers had a type II fiber share similar to young adults (52%) and almost no atrophic fibers. The lifelong endurance athletes looked like the recreationally active group instead: a smaller type II share (39% in the endurance athletes and 35% in the recreationally active men) and more atrophic fibers. The authors concluded that strength training may preserve type II fibers with age. It is a comparison of groups at one point in time, not a trial.
This is not a theoretical concern. Functional power — the ability to catch yourself before a fall, to lift something heavy off the floor quickly, to generate force fast enough to matter in a reactive situation — has been studied as a predictor of functional limitations in later life. In a 2012 review in Exercise and Sport Sciences Reviews, Reid KF and Fielding RA write that muscle power declines earlier and more steeply with age than muscle strength, and that peak muscle power has emerged as an important predictor of functional limitations in older adults.
Why Endurance Athletes Misread This
The mistake is conflating aerobic fitness with physical capacity. A masters triathlete who finishes an Ironman at 60 is genuinely fit in the cardiovascular sense. Their VO2 max, their lactate threshold, their mitochondrial density — all of these are impressive relative to the general population. These numbers would not predict that their power output is in decline.
But the standing broad jump does not care about your VO2 max. Jumping requires rate of force development — the fast-twitch contraction speed that endurance training systematically does not address. That is consistent with the Tøien biopsy findings above, though I could not find a study that compared broad jump distance between older endurance athletes and older strength trainers.
This matters because power is tied to everyday tasks. In the Skelton study, leg power standardized for body weight was related to how quickly people rose from a low chair and how high a step they could manage.
The Standing Broad Jump Test
You do not need a laboratory to measure your power output. The standing broad jump — feet together, quarter squat, swing the arms, jump for maximum horizontal distance — is a common field test of lower-body explosive power that requires no equipment beyond a tape measure and a piece of tape on the floor.
Measure from the tape line to the back of your heels on landing. Three trials, best distance. Record it. Retest every 8 weeks.
What does a good number look like? I could not find well-established broad jump norms for adults in their 60s, so this post does not give a cutoff. The useful comparison is your own number against itself, retest after retest.
How HIIT Rebuilds Power After 50
Jabbour et al. (2017) put 17 young adults (average age 26) and 13 older adults (average age 54.5) through six weeks of short sprint intervals on a bike, three sessions a week. Mechanical efficiency improved in both groups and did not differ between them afterward, and the gains were related to increases in maximal power. It was a small study without a control group, and the older group was in its mid-50s rather than its 60s or 70s.
The signal for type II fiber development is high force production at high velocity. Endurance work does not provide this signal. Heavy resistance training provides the force component but not always the velocity component. The specific combination — moving load fast — is what drives power adaptation.
Practical formats that work for masters-age athletes:
Loaded jumps. Box jumps, broad jumps, and jump squats with light to moderate load (10–20% of bodyweight) performed at maximum effort. Three to five sets of three to five reps, with full recovery between sets. The key is intent — every rep should be maximum velocity, not controlled descent and rise.
Medicine ball throws. Rotational throws against a wall, overhead slams, and chest passes all develop explosive trunk and upper-body power. These are low-injury-risk and appropriate for athletes who are early in the transition from pure endurance training.
Sprint intervals. True sprints — 6 to 10 seconds at maximum effort — are one of the most effective fast-twitch stimuli available. The sprint needs to be genuinely maximal, which means adequate recovery between efforts (90 seconds to 2 minutes) and a low total sprint count per session (6–10 reps maximum).
Hyrox and CrossFit functional movements. The SkiErg, sled push, sled pull, and burpee broad jumps in Hyrox are all power-biased movements. CrossFit's Olympic lifting variations — power cleans, push presses, kettlebell swings — are among the most effective rate-of-force-development stimuli available in a functional fitness context.
The Protocol Card
Two power-focused sessions per week are sufficient for meaningful adaptation. These do not need to be standalone sessions — they can be embedded as the first 15–20 minutes of a strength session, when the nervous system is fresh and capable of true maximal output.
Never train power under fatigue. The moment force production degrades, the session is no longer developing power — it is developing endurance. Treat rest intervals as non-negotiable. The entire point is maximum velocity on every rep.
Test the standing broad jump every 8 weeks alongside your grip dynamometer measurement. These two numbers — grip and jump — tell you more about your functional longevity trajectory than any of the metrics your GPS watch reports.
Endurance training measures what you were built for. Power training measures what you will be able to do in twenty years.
Battle Hard. — Will Power
This article is based on content from The Functional Fitness Protocol (Athlete Series · Book 3). The information presented is educational, not medical advice. Consult a qualified professional before making changes to your training program.
WRITTEN BY
WILL POWER
Founder of Will Power Protocols. Marine veteran, 300+ road races & triathlons, 4x Ironman, USAT Nationals qualifier. Books on strength, longevity & performance after 50 — claims sourced. Not a physician, lawyer, or financial advisor; educational only.
SOURCES
- Jabbour G et al. High-intensity interval training improves performance in young and older individuals by increasing mechanical efficiency. Physiol Rep. 2017;5(7):e13232. PMID 28381445
- Reid KF et al. Skeletal muscle power: a critical determinant of physical functioning in older adults. Exerc Sport Sci Rev. 2012;40(1):4-12. PMID 22016147
- Skelton DA et al. Strength, power and related functional ability of healthy people aged 65-89 years. Age Ageing. 1994;23(5):371-7. PMID 7825481
- Tøien T et al. The impact of life-long strength versus endurance training on muscle fiber morphology and phenotype composition in older men. J Appl Physiol (1985). 2023;135(6):1360-1371. PMID 37881849
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Medical disclaimer. This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration, and nothing on this site is intended to diagnose, treat, cure, or prevent any disease. I share published research as a health enthusiast and endurance athlete, not as a clinician — I do not interpret your results and I do not diagnose. Consult your physician before making changes to your supplement, training, or nutrition regimen, especially if you take prescription medication or have an existing health condition.
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