Load Changes Bench Press Muscle Activation

What’s your best bench? It’s a question often asked in the weight room, and an ongoing goal pursued by many. An interesting study published in the Journal of Strength and Conditioning Research shows how muscle activation patterns can change when lifting close to your one rep max (1RM).
 
Twenty healthy men with a least a year of weight training experience performed single reps with the load increasing from 70% of 1RM, to 80%, 90% and finally 100% of 1RM. At the heaviest load, the pectoralis major becomes a supportive prime mover with the deltoideus anterior taking over as prime mover. The triceps brachii also show greater involvement at 100% of 1RM.