Many trainers prefer the EZ curl bar because it takes stress off the forearm muscles when doing curls. People who do straight bar curls often end up with lower arm strains that feel a lot like shin splints of the forearms. Truman State University researchers, led by Dr. J. Lafrenz, measured muscle activation of the biceps and brachioradialis muscles using electromyography (EMG). EMG measures the electrical activity of muscles – greater EMG activity means greater muscle activation. The biceps were activated most with the straight bar during the positive and negative phases of the lift. The brachioradialis muscle was activated equally with both bars. The results show that the straight bar activates the biceps better than the EZ curl bar. However, use the EZ curl bar if you have forearm strain.
Is it Safe to Lock Out Joints? Trainers often employ a non-locking technique to facilitate the muscle pump. This is especially common in elbow extension movements, such as training biceps and triceps. Some experts warn weight trainers not to lock out joints when doing squats, leg presses, bench presses or curls because of an increased injury risk. Dr. Lee Brown from the University of Arkansas questioned this recommendation. In the knee, for example, minimal contact occurs between the kneecap and femur (large leg bone) during full extension. Brown argues that there is little if any research to indicate that locking out the knee or elbow will cause damage to normal joints with properly performed exercises. And in the normal, uninjured knee or elbow, full extension is the strongest weight-bearing position during axial loading. And fatigue will set in more rapidly if a trainer does not lock out the knee or elbow during some exercises. You will get tired in a hurry if you do squats or military presses with your knees bent.
Brown concluded that most exercises should be performed through the individual’s available range of motion while maintaining proper mechanics. And individual differences and health status may affect the choice of ranges for some exercises. If you feel pain, stop the exercise and evaluate your exercise form and whether you are going to full extension. Weight training is very much an individual endeavor, and no one plan works for everyone. For example, some people are mechanically designed to squat, while others are not and they do the leg press instead. And while some trainers might be able to tolerate locking out during reps, others might find it too uncomfortable. Regardless of your body mechanics, there are definitely situations where going to full extension is not a good idea. Avoid landing on fully extended joints when doing plyometric exercises. Also, avoid doing full knee extensions during the early stages of recovery from anterior cruciate ligament surgery. (NSCA Conference Abstracts; Strength Cond J, published online)