In sculling, each hand controls an oar. In sweep rowing, both hands hold one oar on one side of the boat. Sliding up to the catch, a rower rotates the pelvis and trunk toward the oar while bending sideways to create length. A motion-analysis study found that sweep rowing produced greater trunk lateral bending throughout the stroke and greater pelvic rotation at the catch than sculling (Strahan et al., 2011). Repeating this pattern for hundreds of strokes a practice places different demands on the obliques, erector spinae, multifidus, latissimus dorsi, and shoulder stabilizers on each side.
The asymmetry shows up in the legs and feet too, because power travels from the foot stretchers through the foot, knees, hips, trunk, and shoulders into the handle. In a study of 32 high-performance junior sweep rowers, the outside leg produced more stretcher force than the inside leg, and the difference increased with fatigue during a 2,000-meter race (Mattes and Wolff, 2019). Even though rowers push with both legs, they may not load them equally — especially late in a hard piece, once technique starts to break down.
This imbalance can persist even when a sweep rower trains on an ergometer. Researchers who measured six elite sweep rowers found different left- and right-side activation patterns in the lumbar spine, despite the rowers using less than five degrees of lateral lean (Readi et al., 2015). Another study found no significant left-right difference in rowers’ knee and trunk area, suggesting a stroke can appear symmetrical even when the underlying muscle activation is not (Parkin et al., 2001).
A “muscular imbalance” doesn’t necessarily mean one muscle looks visibly larger — it can also be neuromuscular. A sweep rower’s body learns to recruit one side differently after thousands of one-sided strokes. Ultrasound research actually found symmetrical abdominal-muscle thickness in collegiate single-sided rowers, showing that sweep rowing doesn’t create the same structural changes in every athlete (Gill et al., 2012).
Some asymmetry is a normal, sport-specific adaptation. It becomes a problem once it causes persistent pain, limits range of motion, or ruins technique. Rowers can manage it through single-leg and single-arm strength work, anti-rotation core exercises, balance and mobility training, and more attention to form under fatigue. The goal isn’t perfect symmetry — it’s having enough control on both sides of the body to tolerate the asymmetrical load.