Concurrent training

Concurrent training combines resistance training and aerobic exercise in one program, usually to speed fat loss, improve sport performance or both.^{1Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 164.} Adding endurance work can blunt strength and power gains, an outcome called the interference effect.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 121.} This happens mainly when endurance training is high in intensity, volume or frequency.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 121.} Most studies show heavy lifting doesn’t hurt aerobic power.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 121.}

The chronic interference hypothesis holds that muscle can’t adapt optimally to both kinds of training at once, but its effect in humans on traditional programs is unclear.^{1Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 164.} Aerobic work can also leave residual fatigue that lowers the quality of the next lifting session.^{1Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 164.}

In practice

• Separate the sessions when possible: the closer together they are, the more they interfere, and same-day training interferes more than alternate days.^{3Zatsiorsky, Kraemer and Fry, Science and Practice of Strength Training, 3rd ed., p. 245.}
• If both sessions have to happen on the same day, a long recovery period between them helps.^{4Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 173.}