Shoulders
Although throwing an effective punch requires full-body muscle coordination, your arms and SHOULDERS are the most obvious muscles that you work during a bag session. Crosses and JABS provide a particularly effective workout for your SHOULDER muscles, since straight punches primarily transfer force via rotation of the punching shoulder, which is controlled by your subscapularis, supraspinatus, infraspinatus and teres minor muscles. Wider punches like hooks and uppercuts rely less on core strength, as power is generated by rotational momentum from the triceps and biceps muscles. The constant stream of arm punches that you throw when using a speed bag is particularly effective for working and toning the triceps and biceps
