Strength Training for Female Endurance Athletes: Special Considerations for Relative Energy Deficiency and Bone Density

Why Female Endurance Athletes Need to Pay Special Attention to Strength Training

Female endurance athletes—especially those in long-distance running and long-distance cycling—face a health risk that is easy to overlook: a higher risk of low bone density and osteoporosis. Contributing factors include insufficient skeletal stimulation from chronic low-impact or non-weight-bearing sports (such as cycling and swimming), inadequate energy intake affecting hormones and bone metabolism, and the drop in estrogen that comes with menstrual dysfunction.

Strength training—particularly weight-bearing, high-intensity resistance training—is one of the few interventions that can actively stimulate bone density and counteract these risks. For female endurance athletes, strength training is not just a performance tool; it is insurance for long-term skeletal health.

The “Bone Blind Spot” of Cycling and Swimming

Pure cyclists and swimmers especially need to fill the skeletal stimulation gap through weight-bearing strength training. Research supports that high-intensity resistance training and impact activities (such as plyometrics) offer substantial benefits for increasing or maintaining bone density.

The Warning Signs of RED-S (Relative Energy Deficiency in Sport)

When energy intake chronically fails to keep up with training expenditure, the body shifts into energy-saving mode, affecting hormones, bone metabolism, immunity, and performance—this is RED-S. It does not only affect women, but menstrual status in women is an important early indicator.

Warning signs include: irregular or absent menstrual cycles, recurrent stress fractures, plateauing or declining performance, chronic fatigue, frequent infections, and low mood.

Strength training itself cannot treat RED-S—the fundamental solution is increasing energy availability (eating enough) and seeking sports medicine/nutrition professional help when necessary. But when energy availability is adequate, strength training can provide a positive bone-protective stimulus.

Prescription Principles for Female Strength Training

The training “principles” themselves have no gender difference—women should equally perform high-intensity, progressive maximal strength training and need not fear “bulking up” (female testosterone levels make significant muscle hypertrophy unlikely). The key adjustments are:

1. Emphasize weight-bearing + impact: squats, deadlifts, weighted step-ups, combined with progressive plyometrics (box jumps, bounding) to maximize skeletal stimulation
2. Sufficient intensity: bone adaptation requires relatively high mechanical loading; light weight with high reps provides limited bone density stimulus
3. Energy availability first: training hard under chronic calorie deficit will not improve bone density and instead raises fracture risk

Menstrual Cycle and Training (A Practical Perspective)

Some women feel slight differences in strength and recovery across different phases of the cycle, but individual variation is enormous. Practical recommendations:

• Adjust based on “symptoms” rather than rigid formulas—maintain intensity when you feel good, flexibly modify volume when you feel unwell
• Regularly track your cycle and training sensations to identify your personal patterns
• Do not abandon high-intensity training entirely during a particular cycle phase (no consistent scientific basis for this)

“For female endurance athletes, the most undervalued benefit of strength training is not making you run faster—it is protecting your bone health for the next few decades of your life. Especially for cyclists and swimmers—your sport gives your bones almost no stimulus at all, and the gym is the key to making up that lesson.”

Program Direction (Consistent with General Principles + Bone Strengthening)

• Maximal strength phase: squats, deadlifts 4×4–6, 80%+
• Add impact elements: progressive box jumps, bounding (when your body feels good and energy is adequate)
• In-season maintenance: 1 high-intensity, low-volume session per week
• Ensure adequate energy availability throughout; seek early medical evaluation for any menstrual irregularities

Strength training for female endurance athletes is a dual investment in performance and long-term health. With adequate energy availability, incorporating weight-bearing and impact work into your program means you are not just building race-day fitness—you are building decades of skeletal capital.

Related Reading

• Calcium and Bone Density for Female Athletes: The Unique Risks of Three Endurance Sports
• Athlete Bone Health: The Risks of RED-S and Low Energy Availability
• Relative Energy Deficiency in Sport (RED-S): Causes, Warning Signs, Effects on Bone and Endocrine Health, and How to Seek Help
• Bone Health and Bone Stress Injury Risk in Female Athletes: Low Energy, Menstruation, and the “Normal Bone Density Trap”