The effect of treadmill and overground walking on preferred walking speed and gait kinematics in healthy, physically active older adults

Preferred walking speed (PWS) represents a performance measure of mobility in older individuals. PWS is usually assessed during overground (via a 2-40 m walkway) or treadmill walking in older adults. The aim of this study was to compare the effect of treadmill and overground walking on preferred walking speed, spatiotemporal parameters and foot kinematics in healthy, physically active older and young adults after adequate treadmill familiarization. PWS and spatiotemporal parameters were assessed during overground (PWSO) and treadmill (PWST) walking using two wearable inertial sensor systems and were compared between 25 older (72.2 +/- 4.0, range 66-80 years) and 20 young (24.4 +/- 2.1, range 20-30 years) adults. In the two groups, PWSO (older: 1.45 +/- 0.17 m.s(-1); young: 1.37 +/- 0.16 m.s(-1)) was significantly faster than PWST (older: 1.31 +/- 0.15 m.s(-1); young: 1.25 +/- 0.17 m.s(-1); P < 0.001), with no significant difference between the groups in either walking condition (P = 0.11). The older adults walked with a significantly greater stride frequency (+8%; P 0.001) and lower plantarflexion angle (-5%; P 0.001) than the young participants under both walking conditions. In both groups, treadmill walking was characterized by significantly increased stance (+1%; P = 0.02) and double support (+1%; P = 0.04) duration, as well as reduced swing duration (-1%; P = 0.02) and heel-strike pitch angle (-8%; P < 0.001). Our findings showed that healthy and physically active older and young adults who were adequately familiarized to the treadmill selected a slower PWS on the treadmill than during overground walking with small "safety-related" gait kinematic adaptations. Therefore, treadmill can be used for assessing PWS and gait kinematics in physically active older adults.