In healthy young men, performing intense weight training with or without restricted blood flow to the leg leads to measurable thickening of the connective tissue surrounding the main thigh muscle...

In healthy young men, both intense weight training and intense weight training with restricted blood flow lead to measurable thickening of the connective tissue surrounding the thigh muscle, suggesting this thickening is a common feature of muscle growth under these conditions.

People who start working out with thinner thigh muscles tend to grow them bigger faster than those who start with thicker thighs—but how thick your muscles are at the beginning doesn’t tell you much about how much they’ll grow overall.

In healthy young men, two different resistance training methods—training until muscle failure or using blood flow restriction with mixed intensities—produce similar increases in thigh muscle size after six weeks, suggesting that reaching muscle failure may matter more for muscle growth than how heavy the weights are or how much total work is done.

In healthy young men, two different types of weight training programs—high-intensity lifting and high-intensity lifting with blood flow restriction—produce similar increases in thigh muscle size after six weeks, suggesting that pushing muscles to fatigue with the same number of sets each week matters more for growth than how heavy the weights are.

If you're someone who's been lifting weights for a while, doing the same amount of heavy training over 9 weeks will make your thigh muscles grow by about half a centimeter — whether you spread your workouts over 2 or 4 days a week.