Is aerobic exercise, resistance exercise, or a combination best for reducing cardiovascular disease risk? Original paper

In this 1-year randomized controlled study, aerobic exercise and combined aerobic and resistance exercise — but not resistance exercise alone — improved estimated cardiovascular disease risk compared to no exercise.

The effects of aerobic exercise, resistance exercise, or combined exercise training on cardiovascular risk factors in adults with overweight or obesity.

The primary outcome was a composite cardiovascular disease risk score comprising systolic blood pressure, low-density lipoprotein (LDL) cholesterol, fasting glucose, and body fat percentage. The secondary outcomes included central blood pressure, waist circumference, cardiorespiratory fitness (CRF), and muscle strength.

A total of 406 participants (average age of 50; 53% women, 47% men).

All of the participants were characterized as being “inactive” (i.e., not meeting the current recommendations for aerobic and resistance exercise) and also had high blood pressure and overweight or obesity.

In this 1-year randomized controlled study, the participants were assigned to 1 of 4 groups: an aerobic exercise group, a resistance exercise group, a combined aerobic and resistance exercise group, or a no-exercise control group. All exercise groups exercised 3 times per week.

The aerobic exercise group performed aerobic exercise on a treadmill, stationary bike, or elliptical machine for 60 minutes at 50%–80% of their heart rate reserve.

The resistance exercise group performed resistance exercise for 60 minutes. The exercise sessions comprised 3 sets of 8–12 repetitions of leg press, hamstring curl, quadriceps extension, hip abduction, chest press, lat pulldown, shoulder press, biceps curl, triceps extension, abdominal crunch, lower back extension, and torso rotation.

The combined exercise group performed 30 minutes of aerobic exercise and 30 minutes of resistance exercise of the same type and intensity as the aerobic/resistance exercise groups.

In addition, all of the groups received education on the Dietary Approaches to Stop Hypertension Diet (DASH).

The composite CVD risk score decreased (improved) in the aerobic exercise group and the combined exercise group — but not the resistance exercise group — compared to the control group. Furthermore, the composite CVD risk score decreased more in the aerobic and combined exercise groups than in the resistance exercise group.

Each composite risk factor was also assessed independently. Body fat percentage decreased in the resistance exercise group (−0.9%), the aerobic exercise group (−1%), and the combined exercise group (−1%), compared to the control group. Changes in systolic blood pressure, waist circumference, and LDL cholesterol were not statistically significant compared to those in the control group, although some changes were significant compared to baseline.

The effects of aerobic, resistance, and combined exercise on CVD risk factors and composite CVD risk

In terms of other CVD risk factors, high-density lipoprotein (HDL) cholesterol increased in all of the exercise groups compared to the control group, body weight decreased in the aerobic exercise group (−1.3 kg or 2.9 lb), waist circumference decreased in the aerobic exercise (−1.9 cm) and combined exercise groups (−2.2 cm), and lean body mass increased in the resistance exercise group (+1.2 kg or 2.6 lb).

CRF (i.e., VO₂peak) increased in the resistance exercise (+1.3 mL/kg/min), aerobic exercise (+3.5 mL/kg/min), and combined exercise groups (+2.7 mL/kg/min), but the increase in CRF was greater in the aerobic and combined exercise groups compared to the resistance exercise group. Upper body (chest press) and lower body (leg press) maximal strength increased in the resistance exercise group by +11.3 kg/24.9 lb and +20.3 kg/44.7 lb, respectively, and in the combined exercise groups by +7.3 kg/16.1 lb and +9.8 kg/21.6 lb, respectively, compared to the control group. Improvements were larger in the resistance exercise group than in the combined group.

This trial was not designed to be a weight-loss study per se — the participants weren’t prescribed a calorie-restricted diet or told how much to eat but only educated on the DASH diet (e.g., to limit their sodium intake). The small weight loss observed in the aerobic exercise group and small but nonsignificant weight loss observed in the resistance exercise and combined groups was likely a “side effect” of increased physical activity levels, especially since total energy intake did not change during the study.

Although the participants had overweight or obesity as defined by BMI and waist circumference, they were in good cardiometabolic health. On average, the participants’ blood pressure was only mildly elevated (128 mmHg for systolic and 80 mmHg for diastolic), while fasting glucose (93 mg/dL) and LDL cholesterol (123 mg/dL) were within standard ranges.

In light of the somewhat modest reduction in only a few of the “traditional” risk factors measured, the improvement in “nontraditional” cardiovascular risk factors like CRF and muscle strength deserves attention. VO₂peak increased by 1 metabolic equivalent of task (MET) in the aerobic exercise group and by 0.8 METs in the combined exercise group compared to the control group, though it should be noted that the control group experienced a 1 MET decrease in VO₂ peak at 1 year. For comparison, 1 MET is equal to 3.5 mL/kg/min of oxygen consumption.

CRF is a strong predictor of all-cause mortality. For example, increasing one’s CRF by just 1 MET has been associated with a 13%–19% decrease in the risk for all-cause and CVD mortality.^[1][2] Muscle strength also predicts long-term health outcomes. A reduction of 5 kg in handgrip strength (an indicator of upper body strength) has been associated with an elevated risk for cardiovascular morbidity and mortality, implying that maintaining or improving strength could reduce the risk for these outcomes.^[3]

The logical conclusion from this study is to choose both aerobic and resistance exercise when designing a training program — neither exercise mode alone provides comprehensive benefits for the heart and muscles. Only the combined training group experienced improvements in CRF (VO₂peak) that were greater than those in the resistance training group and improvements in muscle strength that were greater than those in the aerobic exercise group. This occurred despite the fact that the participants in the combined group only spent half of the time engaged in aerobic and resistance exercise as the single-mode exercise groups.

Additional analyses were conducted to estimate changes in 10-year coronary artery disease risk score from baseline to the end of the study. This was accomplished by calculating the participants’ Framingham risk score comprising their age, diabetes status, smoking status, blood pressure, LDL cholesterol, and HDL cholesterol.^[4] By the end of the study, 10-year coronary artery disease risk decreased by 1.1% in the combined exercise group and did not change in the aerobic exercise group or the resistance exercise group.

When HDL cholesterol was added to the original composite CVD risk score, the change slightly improved in the resistance exercise group compared to the control group, though the difference was still not statistically significant.

When the composite CVD risk score was further amended to include central systolic blood pressure, waist circumference, CRF, and muscular strength (the average of upper and lower body strength), this newer composite score was found to improve in the resistance exercise group compared to the control group and was further improved in the aerobic and combined exercise groups compared to the control group.

Which of the individual components of the composite score contributed the most to the change in CVD risk? The largest reduction occurred in percentage body fat, followed by LDL cholesterol, systolic blood pressure, and finally blood glucose.

It’s important to note that lifestyle factors remained similar within and between groups during the year-long study: daily step count, participation in muscle-strengthening activity, total daily energy intake, protein and fat intake, and DASH diet score did not change. However, the participants in the control group did tend to have a higher average daily step count and reported participating in more muscle-strengthening activity outside of their prescribed 3 weekly sessions than the participants in the other exercise groups. This may have influenced the magnitude of the difference between groups in some outcomes, like cardiorespiratory fitness and muscle strength, even though differences were not statistically significant.

Most of the participants in this study were white (a term used by the study authors) and well educated — 49% had a college degree and 42% had completed graduate school. Thus, these results may not be generalizable to other populations.