Bone mineral density (BMD)

Bone mineral density (BMD) is the quantity of mineral deposited in a given area of bone.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.} Osteoporosis combines low BMD with structural changes that make fractures more likely; clinicians diagnose it using a BMD T-score at the lumbar spine or hip.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 798.} About 13% of U.S. adults aged 50 and over have osteoporosis, and 43% have low bone mass.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 798.} Bone loss causes no symptoms, so a fracture is often the first sign.^{3International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 443.}

Forces above a threshold called the minimal essential strain trigger new bone formation at the loaded site.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.} As muscles grow stronger and bigger, the bone carrying their force can adapt too.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.} Peak bone mass is typically reached before age 40, and the drop in estrogen after menopause increases osteoporosis risk.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 92.}

In practice

• Load the sites you want to strengthen with compound exercises such as squats and deadlifts, which send force through the spine and hip.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.} In one study, squats improved femur BMD more than seated leg presses.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.}
• Allow time: bone adaptation takes roughly six months or longer.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 114.}
• Before training a client with osteoporosis, get their fracture history and current BMD.^{3International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 443.}

Where sources differ

ACSM recommends some higher-impact, higher-velocity or higher-intensity resistance training in every osteoporosis program, prioritizing form over intensity for clients who’ve had fractures.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 799.} The IPTA textbook instead advises avoiding high-impact loading such as jumping, as well as spinal flexion and twisting.^{3International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 443.}