The scientific rationale behind the study is deceptively simple. Most research on aging is confounded by inactivity. In England, roughly ninety percent of adults aged seventy-five and above fail to meet recommended guidelines for aerobic and muscle-strengthening exercise, which means that when scientists measure functional decline in typical older populations, they cannot tell how much of the deterioration reflects intrinsic biological aging and how much reflects disuse. The London cyclists were recruited precisely to break that confound. At baseline, participants had to be healthy, free of diagnosed cardiovascular, musculoskeletal or neurological conditions, and training at levels the researchers considered at or above a theoretical set point for healthy aging. By studying people who maintained this activity over nine years, the team hoped to glimpse a model of inherent biological aging, largely unmasked by the negative effects of a sedentary lifestyle.

The primary outcome was peak oxygen uptake, or VO2peak, the gold-standard measure of cardiorespiratory fitness and one of the strongest single predictors of all-cause mortality. The numbers tell a striking story. Across the cohort, VO2peak fell from 44.1 to 35.4 millilitres per kilogram per minute, a decline of 19.7 percent, equivalent to roughly 2.2 percent per year. That figure is considerably steeper than what cross-sectional studies of the general population would predict, with meta-analyses suggesting annualized declines of less than one percent even in sedentary individuals, and around 0.7 percent in master athletes. The discrepancy matters. It suggests that cross-sectional snapshots systematically underestimate the true speed of physiological aging, and that only by following the same individuals over time can researchers capture the real trajectory.

Part of the explanation lies in training volume. Self-reported monthly cycling volume dropped by 33.5 percent over the nine years, and actigraphy worn on the ankle showed small declines in daily light and moderate activity, although sedentary time actually decreased and hard or very hard activity remained unchanged. Intriguingly, neither the change in training volume, nor physical activity levels, nor age itself correlated with the size of an individual’s fitness decline. The researchers also invoke the set point theory of exercise and aging: a hundred-kilometre ride at a given pace for a fifty-five-year-old may represent the same relative physiological challenge as a slower seventy-kilometre ride for an eighty-five-year-old. In other words, absolute training loads fall with age, but the relative stimulus may be preserved, and the fitness values these cyclists retained suggest they remained above the threshold where inactivity begins to erode function.

Benchmarking against the FRIEND reference database made the point vividly. When the cyclists’ follow-up VO2peak values were compared with large age-matched reference populations tested using identical cycle-ergometry criteria, every participant who completed the test except one ranked at or above the ninetieth percentile for their age and sex. Even those who had developed significant illness in the intervening years remained, physiologically, in the top decile of their peers. The mechanistic story behind the decline is also informative: maximum heart rate fell by eleven beats per minute, oxygen pulse dropped, and the ventilatory equivalent for carbon dioxide rose, indicating reduced ventilatory efficiency. When VO2peak was normalized to lean tissue mass rather than total body mass, the decline shrank to 13.7 percent, showing that loss of metabolically active muscle accounted for a meaningful share of the apparent fitness loss.

That body-composition shift was one of the study’s most notable findings. Total body mass and BMI stayed essentially stable across nine years, yet dual-energy X-ray absorptiometry revealed an 8.1 percent loss of lean tissue mass alongside a 20 percent increase in fat mass, pushing average body fat from 23.8 to 29.2 percent. Because these changes occurred in people exercising at high levels, the authors argue that a component of age-related body-composition change must reflect inherent biological aging rather than disuse alone, though reduced training volume and small dietary shifts, including a modest fall in protein intake, cannot be excluded as contributors. The finding carries a practical message: cycling delivers powerful aerobic benefits, but progressive resistance training remains the exercise of choice for preserving muscle mass and strength in older adults, as current physical activity guidelines emphasize.

Not every system declined in lockstep. Resting blood pressure remained unchanged, and fasting metabolic indices, including cholesterol, glucose and insulin, stayed within normal clinical ranges, with total and LDL cholesterol actually falling slightly. Lung function, measured by spirometry, declined more than cross-sectional data would predict, although values remained at or above age-predicted norms. Sleep quality, assessed with the Pittsburgh Sleep Quality Index, did not deteriorate at all, consistent with evidence linking physical activity to better sleep in older people. Measures of submaximal function were also relatively resilient: the ventilatory threshold fell by 14.8 percent relative to body mass but only 8.4 percent relative to lean mass, and it actually rose as a percentage of VO2peak, from 76.7 to 81.8 percent. Oxygen uptake kinetics, the speed at which the cardiorespiratory system responds to a step change in workload, slowed by fifteen percent, yet the overall pattern suggests the capacity to sustain everyday submaximal exercise is better preserved with active aging than maximal capacity.

Perhaps the most human dimension of the study emerged when the researchers classified participants by their returning health status. Thirty-five were optimal agers, still meeting the original strict health criteria; twenty-four were successful agers with no more than two well-controlled conditions; and twenty-three had compromised health, dominated by cardiovascular disease, which accounted for twenty-two of the twenty-three cases. Despite these differences, the physiological trajectories of the three groups were remarkably similar over nine years. The compromised-health group did lose fitness faster, 24.2 percent versus 17.3 percent in the optimal agers, likely reflecting cardiovascular pathology and treatments such as beta blockers and pacemakers that blunt maximum cardiac output. Yet even here, the benchmark against reference populations held: all but one participant remained at or above the ninetieth percentile. Successful agers were physiologically indistinguishable from those entirely free of disease.

The authors are careful about the caveats. Forty-three of the original 125 participants did not return, including eight confirmed deaths, and those who dropped out had higher baseline systolic blood pressure, lower lean mass and lower alcohol consumption than the optimal agers. The retained sample is therefore enriched for the healthiest survivors, and the decline observed in the compromised-health group is likely a conservative estimate. Equipment was replaced with closely matched models, cross-calibrated where necessary, and anchor blood samples confirmed that laboratory changes did not drive the metabolic findings. Female participants, all post-menopausal at both timepoints, showed aging trajectories largely similar to the males, with differences mostly disappearing after normalization to body or lean mass, supporting endurance exercise as an effective strategy for post-menopausal women.

The takeaway is both humbling and empowering. Even in people who cycled for a decade into their seventies and eighties, fitness fell, muscle melted away, fat crept upward and lungs stiffened, at rates that cross-sectional studies had badly underestimated. But against that backdrop of inevitable decline, sustained exercise kept every measured index within the realm of aging physiology rather than pathophysiology, and it did so even in those who developed serious disease along the way. Exercise, the study makes clear, is not a guarantee of disease-free aging, and older endurance athletes may face their own cardiovascular risks. What it does appear to guarantee, for those who keep moving, is a body that continues to perform at the very top of what its age allows, a protective effect on physiological function that persisted through nine years, several diagnoses, and the relentless arithmetic of growing older.

Subject of Research: Longitudinal physiological aging and cardiorespiratory fitness in highly active older cyclists

Article Title: A 9-year longitudinal investigation into physiological aging in highly active older adults

Article References: Fathi, A. S., Francis, T., Milbourn, E., Newton, E., Siegel, L., Taylor, S., Duggal, N. A., Lord, J. M., Lazarus, N. R., Pollock, R. D., & Harridge, S. D. R. (2026). A 9-year longitudinal investigation into physiological aging in highly active older adults. GeroScience. https://doi.org/10.1007/s11357-026-02483-6

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02483-6

Keywords: aging, exercise, cardiorespiratory fitness, VO2peak, cyclists, body composition, lean tissue mass, longitudinal study, geroscience, cardiovascular disease, healthy aging, physical activity