The Golden Retriever Lifetime Study, launched in 2012 by the Morris Animal Foundation, was designed to untangle the dietary, genetic, and environmental risk factors behind four major canine cancers: lymphoma, hemangiosarcoma, high-grade mast cell tumors, and osteosarcoma. Golden Retrievers were chosen deliberately. Roughly half of all deaths in the breed are attributed to cancer, according to data from the Veterinary Medical Database, and the breed shows a markedly elevated incidence of hemangiosarcoma and lymphoma. Because privately owned dogs were enrolled young, between six months and two years of age, and followed with annual questionnaires, veterinary examinations, and biological sampling, the study captures lifestyle exposures years before any diagnosis is made.

In the new analysis, Dennis Ronzani of Ross University School of Veterinary Medicine and Sarah E. Hooper of Arkansas State University examined the activity and lifestyle questionnaire responses of 3,044 purebred Golden Retrievers across the first seven years of the study. During that window, 277 dogs were diagnosed with cancer, with a median age at diagnosis of 6.1 years. The researchers asked a deceptively simple question: could the exercise habits reported by owners, on their own, distinguish dogs that would develop cancer from those that would not?

Answering that question required overcoming a statistical obstacle that has long discouraged researchers from mining longitudinal cohort data. Standard machine learning algorithms assume that every data point is independently sampled, an assumption shattered by repeated annual measurements of the same dog. Classical models, meanwhile, struggle when the number of observations is smaller than the number of predictors. The team turned to a hybrid method called the BiMM forest, developed by Speiser and colleagues, which combines a generalized linear mixed model with a random forest algorithm. This architecture is specifically built to handle clustered, high-dimensional data with nonlinear relationships and interactions between predictors, making it well suited to serial owner reports spanning multiple years.

The researchers built two models. The first used only questions asked consistently from year zero through year seven; the second incorporated additional questions about the pace and duration of exercise that the Morris Animal Foundation added to the questionnaire starting in year three. The difference in performance was dramatic. The years zero through seven model achieved an overall accuracy of just 68.2 percent, while the years three through seven model reached 80.7 percent accuracy, an F1 score of 74.9 percent, and a fair area under the receiver operating characteristic curve of 0.763. The lesson was clear: knowing how briskly and how long a dog exercises carries far more predictive signal than knowing only which activities it performs.

Ranking the predictors by their mean decrease in Gini importance, the team found that the top variables were year in study, exercise frequency, exercise pace, exercise duration, and the frequency of swimming in both warm and cold weather, followed by the owner-reported overall activity level. Four of the ten most important predictors related directly to the frequency and duration of aerobic activity. Perhaps most surprising, the specific type of exercise and the surface on which it took place ranked low in importance. It was the rhythm and intensity of movement, not the movement itself, that carried the strongest association with cancer status.

The data also revealed a poignant behavioral shift after diagnosis. Owners of dogs diagnosed with cancer reported an 8 to 10 percent increase in exercise frequency in the years following the diagnosis, and a 15.6 to 68.88 percent increase in cold weather swimming, while warm weather swimming declined by 2.0 to 13.9 percent. At the same time, exercise pace and duration fell, with dogs diagnosed in year four showing a 7.8 percent reduction in duration and overall activity levels declining by as much as 15.5 percent. The authors suggest this pattern may reflect veterinary recommendations or owner research into the benefits of exercise for canine cancer patients, mirroring the well-documented phenomenon in which roughly three out of four human cancer survivors meet physical activity guidelines after diagnosis.

The findings resonate strongly with human oncology research. Moderate-to-vigorous physical activity is firmly associated with reduced risk of colon, kidney, liver, and mammary cancers in people, and has been shown to delay cancer onset even in women genetically predisposed to breast cancer. Laboratory studies add mechanistic weight: moderate-intensity exercise inhibits cancer cell proliferation and induces apoptosis in animal models, whereas strenuous activity can, in some contexts, promote tumor growth. Notably, most Golden Retrievers in the study exercised at a brisk walking pace for 10 to 60 minutes per session, which qualifies as moderate intensity under the Physical Activity Guidelines for Americans, yet the total weekly volume often fell short of the 150 to 300 minutes recommended for humans, echoing the finding that three quarters of the US population also fails to meet those guidelines.

The swimming data carry their own intriguing, and cautionary, dimension. Dogs diagnosed with cancer swam slightly more often in cold weather before diagnosis, and cold weather swimming rose sharply afterward, possibly reflecting the growing popularity of aquatic therapy and underwater treadmills for canine rehabilitation. But water quality introduces a potential confound. The US Environmental Protection Agency reports that more than 13 million acres of lakes and ponds are impaired by pollution, and epidemiological studies in humans have linked disinfection by-products such as trihalomethanes in chlorinated pools to increased cancer risk. One prior study even found that dogs with urothelial cell carcinoma were more likely to have swum in pools than cancer-free dogs, a connection the authors say warrants closer investigation.

The study has limitations that its authors acknowledge candidly. Because a data embargo restricted the analysis to the first seven years, many dogs had not yet reached the typical age of cancer diagnosis, and fewer than 10 percent of the cohort had a neoplastic diagnosis, too few to build models for individual cancer types. All cancers were therefore grouped together, and missing body condition score data, available for only some dogs and years, prevented the team from accounting for obesity, itself a known risk factor for certain canine cancers. Still, the authors argue that the results point toward a future in which veterinarians can offer evidence-based exercise guidance for dogs, focused on frequency, duration, and pace rather than activity type, and in which cumulative lifestyle exposures, shaped by owner behavior and environment, take their rightful place in canine cancer risk assessment. As more years of Golden Retriever Lifetime Study data become available, the same machine learning approach may reveal whether these patterns hold for specific tumors, and whether adjusting a dog’s exercise routine could genuinely shift its cancer risk.

Subject of Research: Physical activity patterns as predictors of cancer development in Golden Retrievers

Article Title: Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type

Article References: Ronzani, D., & Hooper, S. E. (2025). Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type. Veterinary Oncology, 2(1), Article 11. https://doi.org/10.1186/s44356-025-00024-5

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00024-5

Keywords: Golden Retriever, canine cancer, machine learning, physical activity, Golden Retriever Lifetime Study, veterinary oncology, BiMM forest, exercise frequency, exercise intensity, swimming, cancer risk factors, longitudinal study

The study, conducted by a Brazilian research team using exclusively public data, evaluated all 42 athletes who competed across three modalities: track sprinting, swimming, and weightlifting. These athletes brought impressive credentials, including Olympic and world championship medals, yet their historical personal bests sat on average about 6 percent below the existing world records at the time of competition. That gap matters because the typical difference between two sequential world records in these sports is usually less than 1 percent. In other words, the field entered the event far from record-breaking territory, and the pharmacological protocols on offer would have needed to produce extraordinary gains to close it.

They did not. Across 60 analyzed performances by enhanced athletes, only a single world record fell, set by a male swimmer in the 50-meter freestyle. Crucially, that swim was aided by a polyurethane suit of the kind banned in World Aquatics competition, a piece of equipment notorious for its buoyancy and hydrodynamic advantages rather than any biological effect. The same 50-meter freestyle record had already been broken under full World Anti-Doping Agency compliance just weeks earlier, in March 2026, without such a suit, which the authors note suggests the promised gains from the drug protocols were not as effective as advertised. In track and field, not a single athlete surpassed a personal best, and performances drifted further from world-record pace after the Games than before them.

The physiological rationale behind the event’s protocols was not baseless. Anabolic-androgenic steroids and growth hormone reliably stimulate muscle protein synthesis, producing chronic gains in lean mass and maximal strength, while recombinant erythropoietin elevates hemoglobin mass and oxygen-carrying capacity, improving maximal aerobic capacity in laboratory settings. Historical precedent appeared to support the enterprise: the state-sponsored doping program of the German Democratic Republic between the 1970s and 1980s yielded roughly 150 Olympic medals, and high-profile scandals from BALCO to the Russian scheme in Sochi reinforced the perception that pharmacology delivers results worth the risk. Yet an umbrella review cited by the researchers found insufficient evidence directly linking these substances to improved on-field competitive performance, a distinction between laboratory adaptation and real-world outcome that proved decisive in Las Vegas.

According to the publicly available clinical trial registration associated with the Games, the protocol involved 25 weeks of various testosterone esters and derivatives, with most participants using testosterone, more than half using stimulants, and a minority using erythropoietin or additional anabolic steroids. The authors caution that actual doses and exact substances were never disclosed, leaving open the possibility that administration fell within clinically recommended ranges insufficient for meaningful performance enhancement. They also note that gains in muscle mass and force do not always transfer to sport-specific outcomes, where hydrodynamics, aerodynamics, technique, and neuromuscular timing impose demands that hypertrophy alone cannot satisfy.

On the individual level, the picture was mixed but underwhelming. Nineteen new personal bests were achieved out of 60 enhanced-athlete performances, all in swimming or weightlifting, representing a genuine if modest accomplishment given that most competitors were past their athletic prime. Athletes who set new personal bests improved by roughly 3 percent on average, while the remaining 41 performances declined by about 5.6 percent relative to prior marks. Weightlifting showed the greatest variability, with three athletes achieving new bests while eight regressed, some by double-digit margins. Swimming was the only modality in which the overall gap to world records remained comparable to the historical pre-Games gap, a result the authors suggest may have been confounded by the permitted use of banned polyurethane suits rather than the drug protocols themselves.

Age emerged as a more plausible explanation for the few successes than pharmacology. Athletes who set new personal bests were, on average, closer in age to the point at which they had previously peaked, roughly five years removed from their best performances compared with seven years for those who regressed. Peak performance in sprinting, swimming, and weightlifting generally occurs in the early to mid-twenties, and the researchers argue that a smaller age gap, combined with the enhancement protocol, likely drove the improved marks rather than any dramatic drug effect. If the protocols had been as powerful as claimed, they contend, performances should have exceeded expectations across the board, which was not the case for the majority of competitors.

The event’s third core promise, that enhancement could offset age-related decline and even support longevity, fared worst of all. Using a linear mixed-effects model with athlete identity as a random intercept, the team examined the relationship between the number of years elapsed since each athlete’s personal best and the percentage change in performance at the Games. The slope was negative, meaning performance tended to worsen as time since peak increased, and while the association did not reach statistical significance at the conventional threshold, the authors note that this direction of effect directly contradicts the claim that drug protocols could counteract aging. Physical capacities such as maximal strength, power, and aerobic function are well documented to decline after the third decade of life, and nothing in the Las Vegas data suggested pharmacology had reversed that trajectory.

Perhaps the most pointed observation concerns the handful of athletes who competed without any enhancement at all. Four athletes self-declared as non-enhanced, and their six performances were on average closer to their personal bests, about 1 percent below, than the enhanced athletes’ aggregate 3 percent deficit. One non-enhanced swimmer achieved two new personal bests, and a non-enhanced sprinter came closest among track competitors to surpassing his own record. The sample is far too small for definitive conclusions, and self-declared status was never independently verified, but the pattern reinforces a conclusion the authors emphasize throughout: elite athletic performance is multifactorial, shaped by training quality, injury history, technique, and psychology, and not determined by pharmacology alone. The study has clear limitations, including the absence of dose information, no age-matched control group, and the inherent constraints of retrospective observational analysis of publicly available data. Even so, the collective evidence indicates that the Enhanced Games failed to deliver on all three of its central promises, generating one suit-assisted world record, a minority of new personal bests concentrated in swimmers and lifters, and no detectable attenuation of age-related decline. The human body, it turns out, may indeed be an incomplete project, but the pharmaceutical toolkit on display in Las Vegas was not the shortcut its promoters promised.

Subject of Research: Performance outcomes of doping-permitted competition at the inaugural Enhanced Games

Article Title: Enhanced but not superior: Performance outcomes from the inaugural enhanced games

Article References: Azevedo, R. A., Coutinho, L. F., Gonçalves, M. C., Oliveira, H. A., Gonçalves, G. J., Campos, M., Roschel, H., & Gualano, B. (2026). Enhanced but not superior: Performance outcomes from the inaugural enhanced games. Physiological Reports, 14(19), Article e71123. https://doi.org/10.14814/phy2.71123

Image Credits: AI Generated

DOI: 10.14814/phy2.71123

Keywords: Enhanced Games, performance-enhancing drugs, anabolic steroids, erythropoietin, world records, athletic performance, aging, anti-doping, physiology, swimming, weightlifting, track and field