The Effect of Intensity on 3-Dimensional Kinematics and Coordination in Front-Crawl Swimming

Background: Coaches are often challenged to optimize swimmers' technique at different training and competition intensities, but 3-dimensional (3D) analysis has not been conducted for a wide range of training zones. Purpose: To analyze front-crawl 3D kinematics and interlimb coordination from low to severe swimming intensities. Methods: Ten male swimmers performed a 200-m front crawl at 7 incrementally increasing paces until exhaustion (0.05-m/s increments and 30-s intervals), with images from 2 cycles in each step (at the 25- and 175-m laps) being recorded by 2 surface and 4 underwater video cameras. Metabolic anaerobic threshold (AnT) was also assessed using the lactate-concentration velocity curve-modeling method. Results: Stroke frequency increased, stroke length decreased, hand and foot speed increased, and the index of interlimb coordination increased (within a catch-up mode) from low to severe intensities (P <=.05) and within the 200-m steps performed above the AnT (at or closer to the 4th step; P <= .05). Concurrently, intracyclic velocity variations and propelling efficiency remained similar between and within swimming intensities (P >.05). Conclusions: Swimming intensity has a significant impact on swimmers' segmental kinematics and interlimb coordination, with modifications being more evident after the point when AnT is reached. As competitive swimming events are conducted at high intensities (in which anaerobic metabolism becomes more prevalent), coaches should implement specific training series that lead swimmers to adapt their technique to the task constraints that exist in nonhomeostatic race conditions.