Is it true that men typically have more upper body strength than women?

In 2012, Naomi Kutin, a 10-year-old, could have been the strongest girl in the world. At a weightlifting competition in Corpus Christi, Texas, the 99-pound (44.9-kilogram) Kutin deadlifted an impressive 209.4 pounds (94.9 kilograms) and squatted slightly less [source: Zeveloff]. To grasp the scale of this remarkable achievement, Kutin lifted 215 percent of her body weight—equivalent to what a 180-pound (81.6-kilogram) adult man might squat [source: Cross Fit].

Despite her young age, Kutin's feat is all the more remarkable given her female physiology. Gender disparities in athletic performance have lessened in recent decades as more opportunities for women in sports have emerged and as funding and attention for female athletic training have increased, aided by initiatives like the Title IX law in the U.S. However, intrinsic physical differences between men and women remain, such as men’s superior upper body strength. While Naomi Kutin can outlift her male peers, she remains an extraordinary exception.

Women's lower body strength is generally more comparable to men's, but their upper body strength is often only about half of that of men. A 1993 study on gender differences in muscle composition found that women had 52 percent of men's upper body strength, which the researchers partly attributed to their smaller muscles and greater proportion of fatty tissue in the upper half of the female body [source: Miller et al]. A similar study in 1999 showed that women had 40 percent less upper body skeletal muscle [source: Janssen]. Even when accounting for athletic ability, men still show superior upper body strength; an experiment comparing the hand grip strength of non-athletic men to elite female athletes still revealed a muscle power advantage for men [source: Leyk et al].

Acknowledging this gender gap doesn't mean women can't defy this biological tendency and build their strength, especially in weight-lifting. However, men have an inherent advantage due to their higher levels of testosterone. This hormone has anabolic effects, which means it helps promote muscle growth. Produced by the pituitary gland, testosterone binds to skeletal muscle cells and stimulates protein growth, the building blocks of muscle [source: Roundy]. However, testosterone may also decrease men's strength in the long term.

Are women better at endurance than men?

One clear example of biological differences in strength is the pull-up. For many men, pulling themselves up to eye level with an overhead bar is effortless. However, for women, it's a different story. In fact, the U.S. Marines require male recruits to complete at least three chin-ups to pass their physical entrance test, but female candidates aren't asked to do even one [source: Parker-Pope]. This doesn't mean that women in the military are excused, but rather that the female body is not optimized for this exercise due to factors like weight distribution and lower levels of testosterone-driven muscle mass.

While short bursts of energy required for weight lifting may not be a strength of the female body, as more women participate in endurance sports like marathons, conflicting studies have sparked debate over whether women are better suited for long-distance events than men. While the fastest male runners outperform the fastest female runners, due to factors like muscle mass, higher oxygen intake, and lower resting heart rates, some research suggests that in ultradistance running (over 30 miles or 48 kilometers), women's higher body fat percentage can provide more efficient energy reserves than men's leaner, more muscular bodies. The fat stores are slower to burn, offering lasting energy [source: Maharam]. Additionally, estrogen may protect against muscle fatigue, although its effects vary depending on the athlete and race conditions [source: Crowther]. These biological advantages might explain the rise of women in grueling races like the Iditarod, the Alaskan dog sledding race, where women claimed championships four years in a row from 1985 to 1988 [source: Library of Congress].

What is indisputable, however, is that women excel at the ultimate test of endurance: life itself. Even with global improvements in public health increasing lifespans, women still live an average of five to six years longer than men [source: Kirkwood]. Evolutionary biology suggests that the female body, having evolved for childbirth, is more resilient, with enhanced cellular repair capabilities [source: Dillner]. Another factor contributing to this life expectancy gap could be testosterone, the hormone responsible for male upper body strength. In addition to its anabolic (muscle-building) properties, testosterone also has androgenic (masculinizing) effects, which might encourage riskier behaviors in men, ultimately shortening their lifespans. However, maintaining muscle mass through exercise may help mitigate the more harmful effects of testosterone.