The key to 360-degree muscle: 90-degree eccentric isometrics . It might seem like weāre throwing a lot of geometry at you, but the concept behind time under tension (TUT) is simple, says Joel Seedman, PhD, owner of Advanced Human Performance : āPerform the lowering phase of a movement in a slow, controlled fashion, usually 3 to 5 seconds; pause in the stretched position, typically around 90 degrees; then perform the lifting phase in a powerful yet controlled fashion.ā Believe us, a time-under-tension workout can humble even seasoned liftersā¦Eccentric isometrics are like the pressure cooker of training. āRather than mindlessly performing slow-tempo reps, youāre using the increased time under tension as a means to fine-tune your body mechanics and alignment, which requires more mental engagement and focus,ā Seedman adds. If you want to forge functional muscle mass and strength while simultaneously bulletproofing the joints and connective tissue, give this 10-move, full-body eccentric i...