Practical points on boat acceleration

Like many other biomechanical variables (e.g., force curve), the BA curve is a resultant indicator, and not a target itself and it is superfluous to attempt to “draw” a perfect curve directly. Instead, the focus should be on the rower’s technique: proper rhythm and timing at the catch (Catch Factor), synchronisation in a crew, body segment sequence (Rowing Style), gradients and coordination of stretcher-handle forces, etc. However, BA is a good indicator and may help to detect and improve technical problems, so here we will explain a few points of attention on the BA curve.

High magnitude of the first BA positive peak (7) is a good indicator of the “trampoline effect” (RBN 2006/2), active “connection” of the blade to the water and a steep force curve gradient (increasing) at the beginning of the drive. After the first peak, BA decreases, so BAG crosses zero downwards at this moment and becomes negative (8). This gap is the proper distribution of accelerations between the boat and rower(s) masses during the drive related to the “transition point” (RBN 2008/07).

At this moment, heels are usually placed on the footboard, which increases the stretcher force (not directly, but by means of shortening its leverage at the hips) and rower’s CM acceleration (10) but decreases the boat acceleration. Reminder: the stretcher force is internal and does not affect movement of the whole system, but only distributes emphasis between the rower’s and boat accelerations.

The magnitude of the positive BA peak reflect the distribution between accelerations of the boat and rower’s masses, but not the whole system. To achieve the highest positive BA peak, a rower should quickly cut the pressure on the foot-stretcher and even start pulling it with the feet, combined with an aggressive tug on the handle, “winding up” the body on the handle. This is commonly done when trying to remove water from the boat via the stern deck, which requires the highest positive BA, but for a short time only, by means of a transfer of rower’s kinetic energy to the boat. However, to create the continuous blade propulsive force, a pair of forces is required at the handle and stretcher-gate, so the rower must push the stretcher as long as possible to maintain the acceleration of the whole system.

©2023 Dr. Valery Kleshnev www.biorow.com