The purpose of this study was to assess the difference in maximal physiological responses between an acute bout of deep-water running (DWR) and treadmill running (TMR) in young and older adults. Participants were 9 young and 9 older women who performed maximal DWR and TMR tests. Maximal measures included oxygen consumption (VO2max), heart rate (HRmax), ventilation (VE), respiratory-exchange ratio (RER), and blood lactate (BLac). The young women exhibited higher VO2max, HRmax, VE, and BLac than did the older women for both exercise conditions (p < .05). Lower VO2max and HRmax values were observed with DWR for both age groups (p < .05). No significant differences were found for VE, RER, and BLac in either group between exercise conditions, nor a significant interaction between exercise conditions or ages for any of the variables measured. The data suggest that although older adults exhibit lower maximal metabolic responses, differences between DWR and TMR responses occur irrespective of age.
Kelly S. Chu, Edward C. Rhodes, Jack E. Taunton and Alan D. Martin
Christopher Napier, Christopher L. MacLean, Jessica Maurer, Jack E. Taunton and Michael A. Hunt
High magnitudes and rates of loading have been implicated in the etiology of running-related injuries. Knowledge of kinematic variables that are predictive of kinetic outcomes could inform clinic-based gait retraining programs. Healthy novice female runners ran on a treadmill while 3-dimensional biomechanical data were collected. Kinetic outcomes consisted of vertical impact transient, average vertical loading rate, instantaneous vertical loading rate, and peak braking force. Kinematic outcomes included step length), hip flexion angle at initial contact, horizontal distance from heel to center of mass at initial contact, shank angle at initial contact, and foot strike angle. Stepwise multiple linear regression was used to evaluate the amount of variance in kinetic outcomes explained by kinematic outcomes. A moderate amount of variance in kinetic outcomes (vertical impact transient = 46%, average vertical loading rate = 37%, instantaneous vertical loading rate = 49%, peak braking force = 54%) was explained by several discrete kinematic variables—predominantly speed, horizontal distance from heel to center of mass, foot strike angle, and step length. Hip flexion angle and shank angle did not contribute to any models. Decreasing step length and transitioning from a rearfoot strike may reduce kinetic risk factors for running-related injuries. In contrast, clinical strategies such as modifying shank angle and hip flexion angle would not appear to contribute significantly to the variance of kinetic outcomes after accounting for other variables.