While strength training gives valuable muscular gains it doesn’t give the heart health benefits of aerobic exercise, according to new research from Iowa State University.

The newly-released research – Aerobic, resistance, or combined exercise training and cardiovascular risk profile in overweight or obese adults which was published in the European Heart Journal, found that either full cardio or half-strength, half-cardio are the most effective exercise programmes to protect the heart.

Evidence from other studies show strength training has further benefits, such as improving glucose metabolism, body composition (lean mass) and muscular strength.

The one-year randomised control exercise trial included 406 participants aged between 35 and 70. All participants met the criteria for being overweight or obese; had slightly elevated blood pressure, but weren’t taking medications; were non-smokers and prior to the study were not meeting activity guidelines. However, the participants were predominantly white and well-educated which does limit the scope.

Researchers randomly assigned participants to one of four groups: no exercise, aerobic only, resistance only, or aerobic and resistance. Those in the exercise groups worked out under supervision for an hour, three times a week for a year.

Workouts were tailored to fitness levels and health conditions, with built-in progression. Physical activity and diet data outside the lab was also taken into consideration. All participants, including the non-exercise group, wore pedometers.

Researchers measured blood pressure, low-density lipoprotein cholesterol, fasting glucose and body fat percentage – all cardiovascular disease risk factors – at the start, at the midway point and at the conclusion of the trial.

Results showed that the percentage of body fat in all three exercise groups had decreased significantly compared to the no-exercise control group, but taking all four cardiovascular disease risk factors into consideration, the aerobic and combined exercise groups had lower composite scores than the control group.

Those in the aerobics-only group saw best improvements in the VO2 max test and the resistance-only group saw the biggest gains in the maximal bench and leg press tests for muscular strength.

However, the combination exercise group saw improvements in both aerobic fitness and muscular strength, suggesting that a 50/50 mix between strength and cardio is the best way to train, said the researchers.

Meta-analysis suggests that aerobic or combined exercise is generally superior to resistance exercise when it comes to blood pressure, body fat, glucose metabolism and lipid profile.

Observational studies also suggest that combined exercise provides larger risk reductions in developing clinical endpoints such as metabolic syndrome, hypercholesterolaemia, obesity and cardiovascular morbidity or mortality.

The data suggests that shorter durations of aerobic or resistance exercise – even less than one hour a week – may be sufficient to provide substantial cardiovascular benefits, with diminishing returns with increasing exercise time. This may explain the significant improvement in the composite cardiovascular risk profile with the half-aerobic and half-resistance exercise group.

Researchers found that lean mass at one year was only found in the resistance group, compared to the control group, which might make strength training more appealing for those looking to improve their body aesthetics, as well as for those who are less mobile and find cardio exercise difficult.

“Combined resistance plus aerobic exercise could be considered to increase both cardiorespiratory fitness and muscular strength that are also important to attenuate the harmful effects of obesity on cardiovascular disease prevention and longevity,” said the researchers.

The study was designed to induce no or negligible weight loss to investigate the independent effects of exercise on cardiovascular disease risk factors. However, the findings of -1 per cent body fat reduction is associated with -3 per cent, -4 per cent and -8 per cent lower risks of developing cardiovascular disease risk factor of hypertension, hypercholesterolaemia and metabolic syndrome respectively.