You want bigger arms? The underhand grip requires significant work from the biceps and provides higher direct loading than any isolation exercise. Since most guys train the biceps with lighter, higher-rep sets, they're not placing the muscles under a lot of tension to spur new growth.
While metabolic stress and long-duration sets play a role in hypertrophy, it's important to stimulate fast-twitch fibers with heavy loads. The underhand bent-over row does a good job of this.
What to Do
- Grab the bar with a double underhand grip, slightly outside shoulder width.
- Hinge over by pushing your hips back with the abs braced and shoulders retracted to weld your spine. The bar should sit slightly below the knee as long as the lower back stays flat and the trunk engaged.
- Drive the elbows back until they're even with your body and the bar nears your abdomen. Remember to stick your chest out while pulling the shoulders down and back.
- Squeeze for maximal muscular contraction for a one-count, and then slowly lower the weight under control to the starting position.
Overall, it's imperative to hold position with eccentric control and stability through the trunk while the limbs are moving – a true function of a strong core.