The research matters because hamstring injuries remain one of the most common problems in running and sprinting sports, and advancing age may compound that risk. Programs built around the Nordic hamstring exercise, in which athletes kneel and resist a forward fall to load the hamstrings eccentrically, have been shown to cut hamstring injury rates by up to 51 percent in athletic populations. Instrumented versions of the test, using devices that quantify the force generated as the athlete resists the descent, have become standard screening tools in elite junior, collegiate, and professional cohorts. Until now, however, no reference values existed for older athletes, leaving practitioners to interpret senior athletes’ scores against benchmarks derived from much younger bodies.

The research team set up a performance assessment area at the Huntsman World Senior Games, an annual event that draws more than 11,000 athletes competing in over 40 sports. Across the 2022 and 2023 games, 203 registered athletes, 100 of them female, completed the testing protocol. Each participant warmed up, performed three submaximal Nordic hamstring repetitions at roughly 50, 75, and 90 percent of perceived effort, and then completed three maximal-effort trials separated by 60 seconds of rest. During each repetition, athletes were instructed to resist forward descent as long as possible, and the peak force recorded for each limb was captured by the instrumented device. Reliability testing in a separate sample using the same protocol demonstrated high within-session reliability for peak eccentric force.

The headline numbers are striking. Mean unilateral absolute peak force was 156 newtons in female athletes and 242 newtons in male athletes. When normalized to body mass, those figures correspond to relative values of 2.46 and 2.99 newtons per kilogram, respectively. Median values across the full sample were 186.25 newtons in absolute terms and 2.66 newtons per kilogram in relative terms, with observed forces ranging from 57.25 to 496.75 newtons. The sex difference was very large in absolute terms, with a Cohen’s d effect size of 1.54, and remained moderate even after normalization to body mass, with a d of 0.76. That persistence matters: it suggests body mass alone does not explain the disparity, pointing instead to possible contributions from differences in lean mass distribution, limb dimensions, muscle architecture, tendon properties, and neuromuscular characteristics, along with menopause-related reductions in muscle mass and neuromuscular function in older women.

Age left its mark on the data in a way that surprised no one physiologically but still carries weight practically. Each additional year of age was associated with 2.10 newtons less absolute peak force and 0.020 newtons per kilogram less relative peak force. Expressed practically, a ten-year increase in age corresponded to roughly 21 newtons less absolute force and 0.20 newtons per kilogram less relative force. The regression model for absolute strength explained a moderate proportion of variance, while the relative strength model explained less. Crucially, these declines occurred despite the cohort reporting a median of 660 minutes per week of moderate-to-vigorous physical activity, indicating that sustained athletic participation does not fully prevent age-related reductions in muscle function, even among senior competitors.

The authors interpret the modest magnitude of decline as potentially reflecting partial attenuation of age-related strength loss through continued training. This aligns with broader ageing literature showing that physically active older adults generally retain greater muscle strength and functional capacity than sedentary peers, and with evidence that eccentric strength appears relatively better preserved with ageing than concentric strength, particularly among those performing regular resistance or eccentric training. Masters athlete performance data show progressive reductions in sprint speed, strength, and power output with advancing age, though some evidence suggests these declines may be less steep than previously estimated in highly active older adults. The researchers caution, however, that the analysis was cross-sectional rather than longitudinal, so the observed age association cannot be read as within-person decline over time.

Perhaps the most consequential finding concerns limb asymmetry. Mean absolute asymmetry across the sample was 11.6 percent, with a standard deviation of 8.8 percent and a 75th percentile of 16.1 percent. In younger athletic cohorts, greater eccentric strength asymmetry has been linked to increased hamstring strain injury risk, with one prospective study in elite rugby players reporting that between-limb imbalances of 15 and 20 percent were associated with 2.4-fold and 3.4-fold greater injury risk, respectively. Those findings helped entrench asymmetry thresholds of roughly 10 to 15 percent in screening and return-to-sport settings. Yet in this senior cohort, a quarter of participants exceeded 16 percent asymmetry while continuing to compete at a high level, and asymmetry showed no significant association with either age or sex.

The implication is that common asymmetry thresholds may overclassify high-functioning senior athletes as having concerning inter-limb differences. The authors note that similar asymmetry magnitudes have been reported in healthy older adults, with knee extensor asymmetry values of roughly 10 to 15 percent across middle-aged and older cohorts and mean hamstring asymmetry of about 9 percent in older non-fallers. A systematic review has also cautioned against arbitrary asymmetry cut-points, noting that commonly used thresholds are not robustly supported across the literature. The study’s data support recommendations that asymmetry values be interpreted within population-specific contexts rather than relying on universal cut-points derived primarily from younger athletic cohorts.

For context on how senior athletes compare with younger populations, the reported values sit well below benchmarks from elite and professional cohorts. Elite, subelite, and under-19 rugby players have shown eccentric knee flexor strength values of approximately 343 to 388 newtons, with relative values of 3.65 to 4.03 newtons per kilogram. Elite Australian footballers have demonstrated mean values of roughly 301 to 330 newtons and relative values of 3.81 to 4.18 newtons per kilogram. British track and field athletes have recorded average peak forces of 418 newtons in males and 319 newtons in females, with relative values approaching 5.0 newtons per kilogram in both sexes, and professional soccer cohorts have exceeded 400 newtons in some settings. Even adolescent cohorts commonly demonstrate relative force values near or above 4.0 newtons per kilogram by late adolescence.

The study’s practical payoff is a set of sex-stratified percentile tables, spanning the 10th through 90th percentiles within age bands of 50 to 59, 60 to 69, and 70 and above, that clinicians, coaches, and practitioners can use for benchmarking during athlete monitoring, rehabilitation, and performance testing. The authors acknowledge limitations, including the cross-sectional design, the highly active sample that may not generalize to less active older adults, small subgroups such as males aged 50 to 59, and the use of a specific testing device and protocol that may limit direct comparability with other systems. Injury history, resistance training history, and body composition were not included in the analyses. Still, the work fills a genuine gap: for the first time, practitioners evaluating an athlete over 50 have population-specific reference data rather than benchmarks borrowed from younger bodies, and a reminder that asymmetry numbers once considered alarming may simply be normal for older, high-functioning competitors.

Subject of Research: A cross-sectional study of 203 Masters athletes establishes the first sex-stratified reference values for eccentric hamstring strength measured with instrumented Nordic hamstring testing, quantifying sex and age associations and inter-limb asymmetry in senior competitors.

Article Title: Measuring eccentric hamstring strength in senior athletes: reference values, age and sex associations, and limb asymmetry

Article References: Hinkle, L. J., Mead, J. D., Merrill, E. A., Sponbeck, J. K., Hager, R., & Johnson, A. W. (2026). Measuring eccentric hamstring strength in senior athletes: reference values, age and sex associations, and limb asymmetry. Frontiers in Sports and Active Living, 8, Article 1933413. https://doi.org/10.3389/fspor.2026.1933413

Image Credits: AI Generated

DOI: 10.3389/fspor.2026.1933413

Keywords: Masters athletes, eccentric hamstring strength, Nordic hamstring exercise, aging, injury prevention, limb asymmetry, senior athletes, muscle strength, sports science, reference values, hamstring injuries, biomechanics

The research team, led by investigators at Deakin University in Australia, recruited fifty-six older adults spanning three distinct ageing phenotypes: eleven people with clinically diagnosed sarcopenia, twenty-two non-sarcopenic controls, and nineteen masters athletes with at least ten years of continuous competitive sport participation. Sarcopenia was diagnosed according to the Sarcopenia Definitions and Outcomes Consortium criteria, which combine low handgrip strength with slow usual gait speed. The sarcopenic participants were, on average, the oldest of the three groups at just over eighty years, while the masters athletes were the youngest at around seventy. Crucially, the researchers went to considerable lengths to ensure that age itself did not explain their findings, running sensitivity analyses with age adjustment and an exploratory age-matched comparison that preserved the central results.

The experimental task was elegantly simple in design but technically ambitious in execution. Seated with their preferred leg strapped into an ankle dynamometer, participants performed trapezoidal isometric contractions of the tibialis anterior, the shin muscle that lifts the foot and clears the toes during walking. Each contraction required ramping up to thirty percent of maximal voluntary torque, holding that plateau for twenty seconds, and ramping down again. The tibialis anterior was chosen deliberately: its control is directly relevant to foot clearance during gait, and impaired control of this muscle is linked to trips and falls. Two sixty-four-channel high-density electrode grids were placed over the muscle belly, allowing the researchers to decompose the surface EMG signal into the firing times of individual motor units, the final common pathway through which the nervous system commands muscle.

The dual-task manipulation added a cognitive burden to this motor challenge. While holding the steady contraction, participants were asked to continuously subtract seven from a starting number between seventy and ninety-nine, a classic serial subtraction task used to tax executive function. Trials were invalidated if the subtraction was interrupted for more than three seconds or if multiple errors were made, ensuring that participants genuinely engaged with both tasks. Single-task and dual-task trials were alternated in randomised order to distribute any residual fatigue evenly across conditions. Real-time visual torque feedback was displayed on a monitor with identical settings for every participant, and plateau torque remained close to the thirty percent target in all groups under both conditions, meaning that any differences in motor unit behaviour could not be attributed to differences in the force actually produced.

The headline finding was stark. Torque steadiness, quantified as the coefficient of variation of the force signal, was already poorer in the sarcopenic group during single-task contractions compared with controls and athletes. When the cognitive task was added, steadiness deteriorated further in the sarcopenic participants alone, while controls and masters athletes held their performance stable. In total, the team identified more than 8,300 motor unit spike trains across the cohort, providing an unusually rich dataset. The mean discharge rate of motor units increased similarly in all three groups during dual-tasking, rising by only about 2.6 percent, which told the researchers that the sarcopenic deterioration was not about firing harder or faster. Instead, the problem lay in the timing: the regularity of motor unit discharge, measured as the variability of inter-spike intervals, worsened markedly in the sarcopenic group under cognitive load, while it actually improved in the masters athletes and remained unchanged in controls.

To understand where in the nervous system these differences arose, the researchers turned to intramuscular coherence analysis, a technique that estimates the common synaptic input shared across the motoneuron pool. By summing the spike trains of randomly selected groups of five motor units into cumulative spike trains and computing coherence spectra across up to one hundred permutations, they quantified how strongly different motor units were driven together at different frequencies. Three frequency bands were examined separately, each thought to reflect a different source of shared neural input. Delta-band coherence, spanning one to five hertz, is associated with the low-frequency common drive linked to force fluctuations. Alpha-band coherence, from five to fifteen hertz, is associated with physiological tremor and spinal and afferent contributions. Beta-band coherence, from fifteen to thirty-five hertz, is widely linked to corticospinal coupling, the dialogue between cortex and spinal motor neurons.

The coherence results painted a nuanced picture. Delta-band coherence decreased in all three groups during dual-tasking, suggesting a broad redistribution of low-frequency common input whenever attention was divided, but because this occurred even in the steady performers, it could not explain the sarcopenia-specific loss of force control. The decisive divergence appeared in the alpha and beta bands. Only the sarcopenic group showed an increase in alpha-band coherence under cognitive load, a rise in oscillatory common input that the authors interpret as a form of neural noise, tremor-related activity that is expressed in the force signal and degrades the accuracy of force production. This increase coincided with the greater inter-spike interval variability and torque variability observed in the same participants, although the study design does not establish a causal pathway between these measures. Meanwhile, beta-band coherence rose in the sarcopenic group but fell in controls and, most prominently, in masters athletes, hinting at fundamentally different strategies for regulating cortical input when attention is stretched.

The masters athletes emerged as the most striking contrast in the study. They were the only group whose discharge regularity improved during dual-tasking, and they showed the largest reduction in beta-band coherence, consistent with a flexible, adaptable modulation of common synaptic input. The authors suggest that decades of training in dynamic environments, which demand continuous integration of sensory information, attentional shifting, decision-making and motor execution, may promote more efficient allocation of central resources and more resilient control strategies. Importantly, exploratory comparisons between endurance-type and power-type athletes showed broadly similar dual-task responses, though the small subgroup sizes make those comparisons tentative. The broader message is that neural adaptability in the ageing motor system appears modifiable, and lifelong varied training may be one route to preserving it.

The clinical implications reach well beyond the laboratory. Force steadiness has been linked to mobility performance and postural control, and dual-task ability is strongly connected to fall risk and loss of independence in older adults. In an exploratory analysis drawing on the team’s companion study, a larger dual-task increase in force variability was associated with poorer baseline functional power and mobility, but not with maximal dorsiflexion strength, suggesting that vulnerability to cognitive loading reflects broad functional capacity rather than raw muscle strength. This implies that conventional single-task strength testing may underestimate real-world risk in people with sarcopenia, precisely because everyday activities such as walking, rising from a chair and carrying objects are performed while attention is divided. The findings support interventions that go beyond resistance training alone, incorporating balance-challenging, multicomponent and dual-task exercise programmes that train the nervous system as well as the muscle, and they add momentum to a reframing of sarcopenia as a disease of the ageing motor system rather than of muscle mass alone.

Subject of Research: Neural control of force steadiness during dual-task contractions in older adults with sarcopenia

Article Title: Dual‐Tasking Exacerbates Force and Neural Control Unsteadiness in Older Adults With Sarcopenia

Article References: Orssatto, L. B. R., Clark, B. C., Scott, D., Cabral, H. V., Fernandes, G. L., & Daly, R. M. (2026). Dual‐Tasking Exacerbates Force and Neural Control Unsteadiness in Older Adults With Sarcopenia. Journal of Cachexia, Sarcopenia and Muscle, 17(5), Article e70397. https://doi.org/10.1002/jcsm.70397

Image Credits: AI Generated

DOI: 10.1002/jcsm.70397

Keywords: sarcopenia, motor units, force steadiness, dual-task, high-density EMG, coherence, ageing, masters athletes, neural drive, falls, cognitive load, neuromuscular control