In his 1985 book “The New Encyclopedia of Modern Bodybuilding”, Arnold Schwarzenegger made one off-hand comment that then became the basis for training women differently from men: “[A woman] is probably more interested in shaping and tightening her body than in building big muscles”, therefore women should perform sets of higher repetitions than men. This comment, part of a three-paragraph section on women’s bodybuilding training that primarily states that women can and should train just as hard as men, quickly morphed into the “common knowledge” that women should do higher reps and not focus on lifting heavy weights for fear that they’ll “bulk up”.
We now know that women do not have the testosterone to bulk up like men. In fact, the only way for women to gain bodybuilder-level muscle size without steroids is do precisely what “conventional wisdom” recommends: perform sets of high repetitions at lighter weights, going to absolute failure, with lots of work focusing on muscle isolation.
Women have a slightly slower rate of force production than men, but also a slower rate of fatigue. (1) While there is no need to program different rep ranges for women because of this, this physiological difference between men and women is relevant in planning how much to increase weight or reps in a program.
For example, if a program calls for increasing a weight by 10% for men when going from 10 reps to 8, women may only increase by 5%. Conversely, in an inverse pyramid, women will generally not need to decrease their weight as much when going from 8 reps to 10.
One of the simplest methods for building a comparison of weight vs reps is the Epley formula, which uses a maximal number of reps at a given weight to estimate a one-rep max:
Max = W x R x 0.0333 + W
where W is the weight used, and R is the number of reps performed.
By figuring estimated max weights, the Epley formula can be used to compare sets of different weight and repetitions.
Since women tend to have higher fatigue resistance and slightly lower force production however, the formula can be off slightly. At DEFY! in Broomfield, the training staff has found through thousands of client hours that by using a factor of 0.025 rather than 0.0333, the estimated max more closely predicts the true max.
The attached chart shows how men and women differ in reps at given percentages of their one-rep max. Note that the higher the reps go, the more individual differences - including training experience and fast-twitch vs. slow-twitch muscle fiber composition - will skew accuracy.
Women's training needs do not differ in type from men's, but it does often help to set correct expectations for manipulating sets and reps to get the best results.
(1) Designing resistance programs – Fleck and Kramer