Men vs. women strength gains flip depending on how you measure them
In short
In a 12-week study of 22 men and 19 women with over a year of lifting experience training twice a week, bench press rose 32.8% in women versus 19.9% in men, but that was significant only as relative change. Hex bar deadlift rose 29.4 kg in men versus 14.4 kg in women, significant only as absolute change. Muscle thickness grew about 14% in the biceps brachii and about 10% in the vastus lateralis with no sex difference.
Studies on whether men and women adapt differently to resistance training have produced mixed results. Smith, Behan, Nolan and Egan suspected the disagreement comes from how change is calculated and analyzed the same data three ways: relative change (%), absolute change (kg), and change adjusted for baseline differences with analysis of covariance.
What was the study?
22 men (mean age 29.0, body fat 14.0%) and 19 women (mean age 30.6, body fat 26.3%), each with more than a year of resistance training experience, completed 12 weeks of twice-weekly supervised, periodized, progressive training. Strength was measured as a one-rep max in kilograms and muscle thickness with two-dimensional ultrasound.
How did the results split?
Muscle thickness rose about 14% in the biceps brachii and about 10% in the vastus lateralis, with no statistically significant difference between sexes.
Bench press rose more in women in relative terms, 32.8% versus 19.9% (p = 0.002, d = 1.07), but not in absolute terms. Hex bar deadlift rose more in men in absolute terms, 29.4 kg versus 14.4 kg (p < 0.001, d = 1.15), but not in relative terms.
Someone starting lighter shows a bigger percentage for the same kilograms; someone starting heavier shows more kilograms for the same percentage. The conclusion depends on the yardstick. The authors say physiological differences between the sexes likely contribute too, but which analytical approach was used has to be weighed carefully.
What should you use when reading your own numbers?
A relative strength score is your Big 3 total with bodyweight, age and height corrections, and leaderboards compare within each sex. What this study shows is that the comparison you pick can change the conclusion. When comparing gains with other people, look at kilograms and percent together, and read your own trend against yourself, where the starting level is identical. For the limits of another way to compute relative strength, see strength divided by muscle mass.
The sample is small, 22 men and 19 women, over 12 weeks. These are group averages and are a weak basis for predicting any one person's response.
Frequently asked questions
Do men or women gain more strength from lifting?
It depends on the analysis. In a 12-week study, bench press rose more in women in relative terms (32.8% vs 19.9%), and hex bar deadlift rose more in men in absolute terms (29.4 kg vs 14.4 kg).
Do men and women gain muscle size differently?
Not in this study. There was no statistically significant sex difference, with the biceps brachii thickening about 14% and the vastus lateralis about 10%.
What is the difference between relative and absolute change?
Relative change is the percentage increase from your starting weight; absolute change is the number of kilograms added. A lighter starting weight gives a larger percentage for the same kilograms, and a heavier one gives more kilograms for the same percentage.
Who took part in the study?
22 men and 19 women with over a year of lifting experience completed 12 weeks of twice-weekly supervised, periodized, progressive training. Strength was measured by one-rep max and muscle thickness by ultrasound.
Source: PubMed