Evaluation of book backpack load during walking

This investigation evaluated accumulated mean and peak impact forces per st ride and per metre associated with two book backpack loads and two cadences during single and double support phases of walking. Thirty college partici pants randomly performed three trials while either walking a self-selected cadence or fixed cadence without (empty pack) or with a load (15% body mass ) carried in a bookbag. The fixed cadence (55.5 steps/min) was regulated by a metronome. A computerized Kistler force platform system (phase-locked ti ming device) recorded (200 Hz) three-dimensional reaction forces, impulses, and time in single and double support phases. A Panasonic video camera AG- 450 was set perpendicular to the plane of walking motion to film (60 Hz) th e walking pattern from which stride length and selected kinematic data were determined. Repeated measure ANOVA (p<0.05) determined differences of load s and cadences in walking. Accumulated force was evaluated as impulses per stride and impulses per metre (stress index). When carrying the 15% load. t here was a decrease in speed, a decrease in single support time (SST), and an increase in double support time (DST). The impulses per stride significa ntly increased in DST, and significantly decrease in SST. When impulses wer e analysed per metre, the stress index signficantly increased in DST, but n ot during SST. These differences in SST may be important when load stress i s applied to the single support leg/foot in any given distance of walking. While stride analysis identifies accumulative forces resulting from varying stride lengths, the stress index provides a standardized measure per metre of the accumulative forces that negate the variances of individual stride lengths, and the index measure can easily represent data for any given dist ance traversed.