Resistance training triggers a hormonal response. If it didn’t your body would not respond by increasing muscle mass, strengthening tendons and reinforcing bones. The hormonal changes that occur following training are well-documented in men. Men who do resistance training show marked changes in hormones and marked changes in muscle mass. Men and women both benefit from resistance training. While many fitness sites and health writers tell women that they will not “bulk up” if they add resistance training to their fitness programs, many women are still reluctant to try. What happens to women when they start resistance training?
Womens resistance training and hormones
Men’s hormone profiles change during resistance training. Men undertaking resistance training experience:
- increases in growth hormone (GH)
- increases in insulin-like growth factor (IGF-1)
- increases in testosterone
- reduction in cortisol
But what about women? There hasn’t been as much research on what happens with women. There just aren’t as many research subjects for studies, and possibly less interest. At least in the past. That seems to be changing. A recent paper published by a research team affiliated with the US Army Research Institute of Environmental Medicine looked at changes in womens hormone profiles when they started weight training. It looks like resistance training also causes hormonal changes in women. But the changes may be different. Women showed:
- increases in growth hormone
- increases in total IGF-1
- increases in several IGF-1 binding proteins
- a decrease in free IGF-1
- no change in cortisol
- no change in testosterone
IGF-1 appears to protect or increase bone strength (Courtland 2013). Laboratory animals with low IGF-1 had “older” more fragile bones than animals with higher IGF-1. Growth hormone also maintains tissue and helps maintain strength.
Why do Growth Hormone and IGF-1 matter for women?
Women have less bone and muscle than men to start with. They are more likely to develop osteoporosis than men. Women may also notice the impact of strength loss before men. This can be a serious problem leading to frailty later in life. Frailty is a major factor in loss of independence. Most women already know they should include resistance exercise in their fitness programs. Hopefully understanding why and understanding how it works will help provide a little more motivation.
Some supplement or nutriceutical companies market IGF supplements to women telling them it will increase youthfulness and vitality. You may see claims that the supplements are “safe” and “natural.” To be honest, no one knows if they are safe or not. There simply hasn’t been enough research to know. While IGF-1 may protect bone and muscle some suggest that suppressing IGF-1 leads to a longer life-span. It is also very hard to know how much IGF-1 is in a supplement. You may be getting nothing, or you may be getting an amount that may harm your health in the long run. Supplement contents may be “natural.” But, that is no claim to safety or to effectiveness. Better to keep strong and healthy by eating well and exercising (and including resistance training) rather than trying to tweek your hormone levels. We are the product of millions and even billions of year of evolution. That deserves respect.
Niemann I, Hannemann A, Nauck M, Spielhagen C, Völzke H, Wallaschofski H, & Friedrich N (2013). The association between insulin-like growth factor I and bone turnover markers in the general adult population. Bone, 56 (1), 184-90 PMID: 23792936
Courtland HW, Kennedy OD, Wu Y, Gao Y, Sun H, Schaffler MB, & Yakar S (2013). Low levels of plasma IGF-1 inhibit intracortical bone remodeling during aging. Age (Dordrecht, Netherlands), 35 (5), 1691-703 PMID: 22976122