The researchers reported that body muscle mass (LBM) was related to heart and respiratory fitness among women, outside of body fat percentage.

In a study that included 30 men and 30 women in their 60s, even though women had lower cardiac capacity per unit of body surface area than men, the difference was normalized by total LBM or leg LBM, Dr. David Montero said. , University of Calgary, Alberta, Canada, at a presentation at the ObesityWeek meeting.

“Ultimately, LBM stands out as a strong and independent determinant of female cardiac and aerobic capacity, regardless of body fat percentage, in relationships that do not exist in men,” wrote Montero and colleagues. obesity, where the results of the study were published simultaneously.

“The main aim of this study was to determine the relationship of body composition according to sex.2 responses to female and male exercise intake based on age and physical condition, ”the group explained.

The women in the study presented the dimensions of the right and left heart chambers and the normalized outputs by body surface area compared to the men. Sexual differences in cardiac structure and function, however, were eliminated when normalized by total or leg LBM. Maximum oxygen uptake (VO2 peak) was similar after normalization of total and leg LBM in women and men, although women typically had a lower ability to transport blood oxygen, according to the researchers.

“These findings mean that the number of tissues that are most metabolically active explains the cardiac capacity of individuals (or at least in parallel), regardless of gender,” wrote Montero and the authors. “As a result, a percentage of women with less metabolically active percentages (i.e., body fat) can be considered an inability to bear the weight of the cardiovascular system to promote full-body aerobic work, which is essential for the vast majority of human physical activity.”

The researchers noted that a significant increase in VO (11%) was demonstrated2 peak Following the endurance training of women in the study, but not in men, despite similar increases in LBM in both groups.

“However, a systematic review of the literature indicates a shortage of research that specifically examines this interesting hypothesis,” the group wrote. “Until we understand more, the observation continues that elite female endurance athletes with the highest level of heart-breathing status are usually” heavier “(compared to body height) than their male counterparts, a gap that may not be fully explained by gender differences in body fat percentage. “.

Asked about his point of view, Dr. Mitchell Roslin, head of Bariatric Surgery at Lenox Hill Hospital in New York, said. MedPage Today: “The media has paid close attention to the benefits of things like active living and walking. But it’s probably less talk about doing resistance training – that doesn’t necessarily mean weight, but it can be used. Resistance bands, stretching, squats and muscle training other things that can help build muscle mass or prevent muscle rupture that occurs during natural aging. ”

Roslin said a large difference between men and women is that women have a higher fat distribution, which helps regulate sex hormones.

“It’s related to menopause [a] a decrease in muscle and an increase in fat as fat replaces the lost estrogen, ”Roslin said. The goal is not to lose non-muscle fat, but the truth is that with every successful weight loss program, people lose a lot of muscle. The goal of losing weight is to lose fat, but at least to break down muscle loss, ”he said.

He said more attention should be paid to endurance training. “You don’t have to be in the gym and you don’t have to use weights,” Roslin said. “Everything you need to do in resistance training can be done with some good resistance bands that cost $ 3.99 – and with a good course of instruction.”

For the study, Montero and co-authors hired 60 healthy and moderately active women and men based on age and cardiac-respiratory status. Body composition was determined by double-energy x-ray absorption, and transthoracic echocardiography and oxygen uptake were assessed during established rest and exercise with established methods.

The main cardiac and pulmonary outcomes were normalized by body surface area, total LBM, or leg LBM.

Limitations of the study composition, and 2) three of the participants were taking hormone replacement therapy (HRT), but the researchers said there was no obvious difference in the results of these people compared to others, which is also consistent with previous evidence. HRT has no effect on key cardiovascular variables during VO2 peak and exercise.

  • Ed Susman is a freelance medical writer living in Fort Pierce, Florida, USA.


Montero reported no relationship with the industry.

Roslin introduced her to Medtronics and Johnson & Johnson.