Male runners consistently post faster times than women across nearly all distances. World records for women in Olympic running events, ranging from the 100-meter sprint to the marathon, are approximately 10% to 12% slower than those set by men. This performance gap is not attributable to a single cause but rather to a combination of fundamental physiological and biomechanical distinctions that emerge primarily after puberty. These reasons are rooted in differences in muscle composition, cardiovascular capacity, and skeletal structure.
Hormonal Differences and Muscle Power
The primary factor driving the difference in speed and power is the disparity in circulating sex hormones, particularly testosterone. Testosterone, present at adult male levels far exceeding those in women, is an anabolic hormone that stimulates muscle growth. This results in men having significantly greater skeletal muscle mass, often 25% to 40% more than women, and larger muscle fiber cross-sectional areas.
The larger muscle cross-sectional area directly translates to a greater capacity for force production, which limits sprinting and explosive running. Male athletes also tend to have a lower body fat percentage than female athletes, improving the strength-to-weight ratio for generating power. This hormonal environment also influences muscle fiber distribution, potentially favoring a larger relative area of fast-twitch fibers in men, optimized for powerful, short-duration anaerobic efforts.
Generating high forces against the ground is paramount for acceleration and maximum speed in short-distance events. The hormonal advantage contributes to men possessing superior anaerobic metabolic power, allowing for greater maximal force, velocity, and power output during a sprint. This difference in power output is a key determinant of the performance gap, especially where muscle strength is the main limiting factor.
Variations in Aerobic Capacity and Oxygen Delivery
Beyond muscle power, sustained speed in middle and long-distance running is limited by the body’s capacity to deliver and utilize oxygen, known as maximal oxygen uptake (VO2 max). Men typically exhibit VO2 max values that are approximately 10% to 30% higher than those of women, even when comparing elite athletes. This discrepancy is largely attributed to differences in the cardiovascular and hematological systems.
Men generally have a higher concentration of hemoglobin, the protein in red blood cells responsible for transporting oxygen, which is stimulated by testosterone. Female athletes have mean hemoglobin levels that are about 12% lower than age and race-matched men, reducing the overall oxygen-carrying capacity of the blood. Furthermore, men tend to have larger hearts and lung volumes relative to their body size. This allows for a greater cardiac output—the volume of blood pumped per minute—to supply oxygenated blood to working muscles.
These physiological differences in oxygen transport capacity directly affect sustained running velocity and endurance performance. While the difference in absolute VO2 max is substantial, the gap narrows slightly when aerobic capacity is measured relative to fat-free mass. However, the advantage remains due to the larger skeletal muscle mass in men. The greater aerobic capacity in men is a major reason why the performance gap persists across all running distances.
Skeletal Structure and Running Efficiency
Biomechanical factors related to skeletal anatomy also contribute to the performance difference, particularly in running efficiency and stride mechanics. One structural variation is the female pelvis, which is typically wider than the male pelvis. This wider structure influences the angle at which the femur meets the knee, known as the quadriceps angle, or Q-angle.
A larger Q-angle causes the thigh bone to angle more steeply inward toward the knee, creating a slight mechanical disadvantage during the running stride. This alignment can increase the lateral pull on the kneecap and potentially affect the alignment of the leg, translating to less efficient force transfer from the muscles to the ground. Running mechanics require applying force to propel the body forward, and the narrower alignment in men allows for a more direct application of force.
Beyond the Q-angle, men tend to have a higher center of gravity and longer limb lengths relative to their torso size. This anthropometric difference can result in a longer potential stride length, allowing men to cover more ground with each step. These structural and leverage differences collectively influence the overall mechanical efficiency and optimal stride pattern for running speed.