Brazil trial tested weights plus cardio for older hearts; results pending

A Brazilian university has registered a finished study that asked a simple question many older exercisers might also ask: is mixing weight training with endurance exercise better for the heart than doing just one of them? The study was first posted on the US trial registry ClinicalTrials.gov on November 9, 2026, and is already listed as completed. No results have been posted yet.¹

The trial, numbered NCT07925905, is sponsored by the State University of Pará (Universidade do Estado do Pará).¹ It enrolled 44 adults between 60 and 85 years old and compared three exercise programs: strength (resistance) training on its own, endurance training on its own, and the two combined, which researchers call “concurrent training”.¹

What was registered

According to the registry record, the study started on July 16, 2025, and reached its main completion date on June 30, 2026.¹ That means the record went public several months after the last main measurements were due. The record’s field for posted results is still empty.¹

Each program lasted 12 weeks, with three sessions a week.¹ The registry lists the trial as “interventional”, meaning researchers assigned people to the exercise programs rather than just observing what they chose to do. It is marked “phase NA”, the label used for studies that are not drug trials and so do not follow the drug-testing phases.¹

The researchers explain their reasoning in the summary. They write that population aging in Brazil comes with more heart and blood vessel disease and with a decline in “cardiac autonomic modulation”, the automatic nervous control of the heart. They describe physical training as an essential non-drug way to soften the effects of aging.¹

What the study measured

The main thing the study tracked is heart rate variability, often shortened to HRV. Every listed primary outcome, the measures a study is designed around, is heart rate variability at 12 weeks.¹ HRV describes how much the time between heartbeats changes. The record says it was analyzed in two standard ways, called the “time domain” and the “frequency domain”.¹

The study also looked at several other things, according to the summary:¹

• blood pressure and a related measure called the “double product”;
• blood markers of fats and sugar (lipid and glycemic profiles);
• sleep quality;
• perceived stress.

Those last two are the “behavioral aspects” in the study’s title.¹ The record does not say which of these measures, if any, changed.

Why researchers watch heart rate variability

HRV has been studied in older adults for years. A large US research program called the Cardiovascular Health Study recorded people’s heartbeats over 24 hours with portable monitors. In one analysis of 585 adults over 65, researchers found that one type of HRV, the frequency-based kind, fell most between ages 65 and 70 and then leveled off after 75.² That drop happened whether or not people had higher heart disease risk.² Other types of HRV kept changing with age and were more closely tied to heart disease risk.² That work was funded by the US National Heart, Lung, and Blood Institute.²

A second analysis from the same US study followed 985 older adults over 5 years.³ Its authors wrote that HRV gives measures of how the nervous system controls the heart and that these measures are linked with heart risk.³ They found that people with more leisure-time activity, longer walking distances and a faster walking pace tended to have more favorable HRV readings over time.³ The authors said this suggested possible ways that regular activity later in life might be connected to lower heart-related death.³

That US work was observational. It showed that more active people tended to have better HRV, not that exercise caused the difference. A trial like the Brazilian one is a step closer to that question, because researchers assigned the exercise programs.

What this does not show yet

For now, the registry entry tells readers what was done, not what was found. Without posted results, there is no way to know whether combined training changed HRV, blood pressure, blood markers, sleep or stress more than either type of exercise alone, or at all.

Several other details are worth noting from the record itself:

• Smaller than planned. The summary describes a “projected sample” of 78 participants, while the record lists 44 as the actual enrollment.¹ Smaller groups make it harder to detect real differences between programs.
• No resting group listed. The three interventions listed are all exercise programs.¹ The record does not list a group that stayed inactive, so the study is set up mainly to compare types of exercise with each other.
• Design details are thin. The summary calls it a “prospective clinical trial”, meaning it followed people forward in time.¹ The text provided does not say how people were assigned to groups or whether the people measuring results knew who was in which group.
• Registered after the fact. The record was first posted after the listed completion date.¹ Registering a study before it begins makes it easier for outsiders to check that the reported results match what was planned.
• A stand-in measure. HRV is a measure linked with heart risk in earlier research, not a heart outcome such as a heart attack.³ A 12-week study of HRV cannot show effects on heart disease or lifespan.

Who is behind it

The sponsor listed on the registry is the State University of Pará, a public university in Brazil.¹ The record does not list a company, product or outside funder, and it does not name the investigators in the information available to Biohack. The exercises tested are general training programs, not a branded product or device.¹

How it fits the field

Exercise is one of the most studied ways to support health in later life, and Biohack has covered several trials that use it as the treatment. These include a planned trial of strength training and Alzheimer’s markers and a Chicago trial of exercise to prevent frailty in older women with HIV.

The Brazilian study’s specific angle is the comparison. Many older adults do one kind of exercise, often walking. The US Cardiovascular Health Study linked walking with better HRV over time.³ The Brazilian trial asks whether pairing endurance work with strength work does something different for the heart’s automatic control than either alone, measured over three months.¹ Its design also reflects the age pattern seen in the US data, where some HRV measures change most in the late 60s.² The Brazilian group covered ages 60 to 85.¹

What to watch next

The next step is results. They could appear on the registry, in a journal paper, or both. When they do, the key questions will be how big any differences in HRV and blood pressure were, how many of the 44 people finished, whether any side effects or injuries were reported, and whether the combined program stood out from strength or endurance training alone. Biohack will update this thread when results are posted.

This article is news, not medical advice. Anyone thinking about starting a new exercise program, especially later in life, may want to talk it through with a health professional.