Injury Patterns and Frequency in Swimming: A Systematic Review highlights the lumbar spine as a common injury site due to degenerative changes and high training volumes, noting that regions like the knee and lower back are impacted by the biomechanical demands of the breaststroke.

The Spine is the Tree of Life: A Systematic Review and Meta-Analysis of the Radiographic Findings Related to Spinal Injuries in Athletes explicitly states that conditions like spondylolysis are common in swimmers performing breaststroke and butterfly styles due to repeated flexion and hyperextension of the lumbar spine.

The immediate effect of swimming stroke on pain in people with chronic low back pain: a crossover study demonstrates that breaststroke is associated with higher average and worst pain during swimming compared to other strokes like backstroke.