Resistance training

ACSM lists resistance machines, free weights, resistance bands and body weight exercises as the main types of resistance training.^{1Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 682.} Strength is the first and most obvious change, usually within the first month.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 83.} Visible changes in muscle can follow one to two months into a regular program.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 83.}

Much of the early strength gain comes from neural adaptations, as the brain learns to produce more force from the same muscle.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 46.} Over the long term, the main adaptation is hypertrophy, larger muscle fibers that can produce more force and power.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 91.}

The benefits reach past muscle. Regular resistance training improves body composition, blood glucose, insulin sensitivity and blood pressure in people with mild or moderate hypertension.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 95.} ACSM reports it is as effective as endurance training for managing type 2 diabetes.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 95.} It also increases bone mineral density.^{6Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 28.} The risk of injury is low compared with other sports and conditioning activities.^{7Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 53.}

In practice

• Beginners can train the whole body two or three days a week, on nonconsecutive days.^{8Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 412.}
• Heavier loads for fewer repetitions build strength; lighter loads for many repetitions build muscular endurance.^{9Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 418.}
• To gain muscle, pair progressive resistance training with diet.^{10Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.}
• Resistance training matters more with age, and older adults’ first sessions on machines or free weights should be supervised.^{11Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 444.}
• There is no minimum age for youth resistance training, but participants need enough emotional maturity to take part.^{12Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 511.}