Phase Level Assessment of Ergonomic Intervention Effectiveness in Reducing Knee Musculoskeletal Disorder Risks during Residential Roof Shingle Installation

The prevalence of knee musculoskeletal disorders (MSDs) among roofers due to ergonomically unfavorable kneeling postures during shingle installation is a well-recognized concern. While knee-saving interventions like knee savers (KSs) and knee pads (KPs) have shown potential to reduce MSD risks, their effectiveness across different phases of shingle installation remains unknown. The objective of this study is to assess how interventions of KSs and KPs alleviate risks of MSDs in the knees during various phases of shingle installation. These phases encompass (1) reaching for shingles, (2) placing shingles, (3) grabbing a nail gun, (4) moving to the first nailing position, (5) nailing shingles, (6) replacing the nail gun, and (7) returning to an upright position. To collect data, nine male participants simulated the shingle installation task on a slope-adjustable roof platform (0°, 15°, and 30° slopes) under four intervention conditions: no intervention (NO), with KPs only (KP), with KSs only (KS), and with both KPs and KSs (BO) in a laboratory setting. Knee parameters including maximum flexion, abduction, adduction, and internal/external rotations were measured at all phases to assess intervention impacts through statistical analysis.