Clinical Context

Aerobic exercise has received more attention and promotion as a means to improve health and longevity among adults compared with muscle-strengthening exercise (MSE). A review by Bennie and colleagues, which was published in the August 26, 2020 issue of Sports Medicine Open,^[1] offered a summary of the health benefits of MSE and advocacy for a public health campaign to promote more MSE.

The authors pointed to multiple studies that demonstrate that MSE can improve bone mineral density and alleviate depression and anxiety among adults. Muscle-strengthening exercise is also associated with improvements in cardiometabolic health and the ability to perform activities of daily living. These benefits are in addition to similar benefits conferred by regular aerobic exercise.

Do these positive health effects result in improved mortality outcomes? The current study by Gorzelitz and colleagues addresses this question.

Study Synopsis and Perspective

Older adults who take part in regular weightlifting -- either with or without moderate to vigorous aerobic activity -- show significant reductions in all-cause and cardiovascular disease (CVD) mortality, with the strongest effects observed when the 2 types of exercise are combined, new research shows.

"The novel finding from our study is that weightlifting is independently associated with lower all-cause and CVD-specific mortality, regardless of aerobic activity," first author Jessica Gorzelitz, PhD, told Medscape Medical News.

"What's less surprising -- but consistent and nonetheless noteworthy -- is that weightlifting in combination with aerobic exercise provides the lowest... risk for mortality in older adults," added Gorzelitz, an assistant professor of health promotion in the department of health and human physiology at the University of Iowa in Iowa City, Iowa.

Persons who undertook weightlifting and aerobic exercise in combination had around a 40% lower risk for death than persons who reported no moderate to vigorous aerobic activity or weightlifting. The findings were recently published online in the British Journal of Sports Medicine.^[2]

Physical activity guidelines generally recommend regular moderate to vigorous aerobic physical activity, in addition to at least 2 days per week of muscle-strengthening exercise for all major muscle groups for adults to improve health and boost longevity.

Still, few observational studies have examined the association between muscle strengthening and mortality, and even fewer have looked specifically at the benefits of weightlifting, Gorzelitz said.

To investigate, Gorzelitz and coauthors evaluated data on participants in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, which initiated in 1993 and involved adults aged 55 to 74 years at 10 US cancer centers.

Thirteen years into the trial, in 2006, participants completed follow-up questionnaires that included an assessment of weightlifting (not included in a baseline survey).

Among 99,713 participants involved in the current analysis, the mean age at the time of the follow-up questionnaire was 71.3 years. Participants had a mean body mass index (BMI) of 27.8 kg/m², and 52.6% were women.

Only about a quarter of adults (23%) reported any weightlifting activity within the previous 12 months, with fewer, at 16%, reporting regular weightlifting of between 1 and 6 times per week.

Participants' physical aerobic activity was also assessed. Physical activity guidelines (2018) recommend at least 150 to 300 minutes per week of moderate-intensity aerobic physical activity or 75 to 150 minutes per week of vigorous intensity aerobic activity or an equal combination of the two. Overall, 23.6% of participants reported activity that met the guideline for moderate to vigorous physical activity, and 8% exceeded it.

Over a median follow-up of about 9 years, 28,477 deaths occurred.

Persons reporting weightlifting had a 9% lower risk for combined all-cause mortality and CVD mortality, after adjustment for any moderate to vigorous physical activity (each HR, 0.91).

Adults who met aerobic activity recommendations but did not weightlift had a 32% lower risk for all-cause mortality (HR 0.68), while adults who also reported weightlifting 1 to 2 times per week in addition to the aerobic activity had as much as a 41% lower risk for death (HR 0.59) compared with adults reporting no moderate to vigorous aerobic activity or weightlifting.

The benefit of weightlifting in terms of cancer mortality was only observed without adjustment for moderate to vigorous physical activity and was therefore considered null, which Gorzelitz noted was somewhat surprising.

"We will examine this association further because there could still be a signal there," she said, noting other studies have shown that muscle-strengthening activity is associated with lower cancer-specific mortality.

Of note, the benefit of weightlifting appeared stronger in women vs men, Gorzelitz said.

Underscoring that the results show only associations and not causation, Gorzelitz speculated that mechanisms behind a mortality benefit could include known favorable physiologic changes of weightlifting.

"If people are weightlifting [to a degree] to reap strength benefits, we generally see improvement in body composition, including reductions in fat and improvements in lean tissue, and we know that those changes are associated with mortality, so it could be that the weightlifting is driving the strength or body composition," she said.

The full-body response involved in weightlifting could also play a key role, she noted.

With weightlifting, "the muscles have to redirect more blood flow, the heart is pumping harder, the lungs breathe more and when the muscles are worked in that fashion, there could be other system-wide adaptations," she said.

Furthermore, social aspects could play a role, Gorzelitz observed.

"Unlike muscle strengthening [activities] that can be done in the home setting, weightlifting typically has to be done in recreational facilities or other community centers, and considering that this is an older adult population, that social interaction could be very key for preventing isolation."

Important limitations include that the study did not determine the nature of the weightlifting, including the duration of the weightlifting sessions or type of weight, which could feasibly range from small hand-held weights to heavier weightlifting.

The study also could not show how long participants had engaged in weightlifting in terms of months or years; hence, the duration needed to see a mortality benefit was not established.

Nevertheless, the study's finding that the group with the lowest benefits was the one reporting no aerobic or weightlifting exercise underscores the benefits of even small amounts of exercise.

"I think it's really important to promote the importance of adding muscle strengthening, but also of any physical activity," Gorzelitz said. "Start small, but something is better than nothing."

The authors have reported no relevant financial relationships.

Study Highlights

• Investigators drew study data from the Prostate, Lung, Colorectal, and Ovarian Screening Trial. This trial began enrolling 154,897 US residents between the ages of 55 and 74 years in 1993. The main outcome of this trial was the efficacy of cancer-screening interventions.
• The study included questions about participants’ levels of physical activity, including both MSE and aerobic exercise. The researchers assessed the intensity and frequency of these activities.
• The primary study outcome was all-cause mortality, and the investigators also assessed mortality due to CVD and cancer. Deaths were both reported to study staff by participants’ family members and physicians as well as through the National Death Index.
• The study result was adjusted to account for demographic, health habit (including aerobic exercise), and disease variables.
• 99,713 participants provided data for the current study. The mean age of participants was 71.3 years, and 53.2% were women. More than 90% of the cohort was White.
• 23% of participants reported any weightlifting during follow-up, and 16% of respondents lifted at least weekly on a routine basis. Meanwhile, 32% of the cohort met US national criteria for sufficient aerobic activity.
• There was a strong correlation between participation in MSE and aerobic exercise.
• The HR for overall mortality in comparing participants with any MSE vs no MSE was 0.91 (95% CI: 0.88, 0.94).
• The respective HR for cardiovascular mortality was similar (HR 0.91 [95% CI: 0.86, 0.97]). MSE was not effective in the prevention of cancer-related mortality.

Figure. Benefits of Weightlifting Related to Mortality

• MSE at a frequency of 1 to 2 times per week was associated with an even greater improvement in the risk for death (HR 0.86 [95% CI: 0.82, 0.91]), but more frequent MSE did not further improve mortality outcomes.
• The HR for mortality for adults meeting vs not meeting the national aerobic exercise threshold was 0.68 (95% CI: 0.65, 0.7).
• MSE and aerobic exercise were synergistic in preventing death vs no physical activity.
• Women experienced a greater mortality benefit associated with MSE compared with men, but age, race, BMI, educational attainment, and smoking did not affect the main study result.

Clinical Implications

• A previous review by Bennie and colleagues found that MSE can improve bone mineral density and alleviate depression and anxiety. MSE is also associated with improvements in cardiometabolic health and the ability to perform activities of daily living. These benefits are in addition to similar benefits conferred by regular aerobic exercise.
• The current study by Gorzelitz and colleagues demonstrates that MSE among older adults can reduce the risk of all-cause and cardiovascular mortality, but MSE did not affect the risk of cancer-related mortality.

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