It has been suggested that the uniquely large gluteus maximus (GMAX) muscles were an important adaptation during hominin evolution based on numerous anatomical differences between humans and extant apes. GMAX electromyographic (EMG) signals have been quantified for numerous individual movements, but not across the range of locomotor gaits and speeds for the same subjects. Thus, comparing relative EMG amplitudes between these activities has not been possible. We assessed the EMG activity of the gluteal muscles during walking, running, sprinting, and climbing. To gain further insight into the function of the gluteal muscles during locomotion, we measured muscle activity during walking and running with external devices that increased or decreased the need to control either forward or backward trunk pitch. We hypothesized that 1) GMAX EMG activity would be greatest during sprinting and climbing and 2) GMAX EMG activity would be modulated in response to altered forward trunk pitch demands during running. We found that GMAX activity in running was greater than walking and similar to climbing. However, the activity during sprinting was much greater than during running. Further, only the inferior portion of the GMAX had a significant change with altered trunk pitch demands, suggesting that the hip extensors have a limited contribution to the control of trunk pitch movements during running. Overall, our data suggest that the large size of the GMAX reflects its multifaceted role during rapid and powerful movements rather than as a specific adaptation for a single submaximal task such as endurance running.

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Traditionally total knee arthroplasty (TKA) design has been based on theories of the movement of the healthy knee joint. Currently, there are two competing theories on the flexion/extension axis of rotation of the knee with disparate radii of rotation, and thus differing movement patterns. The purpose of our study was to compare stair ascent kinematics and kinetics of single-radius (SR) and multiradius (MR) TKA subjects. We hypothesized that the knee kinematics and kinetics of SR TKA patients would more closely replicate healthy age matched controls during stair ascent than MR TKA patients, 1 year after TKA. Both patient groups had large improvements in biomechanical and clinical outcome measures following surgical intervention. However, the SR knee design performs closer to healthy controls than MR knees during stair ascent, supporting results that have been previously obtained for level walking. SR TKA subjects demonstrated reduced power production and sagittal moment compared with controls, albeit more than MR TKA subjects. This study demonstrates that patients who receive SR TKA have kinematics more closely aligned to normal patterns postoperatively than those who received an MR TKA. The power production and sagittal moment of the healthy controls most closely match previously published values of younger adults, SR TKA group most closely matches older adults, while the MR TKA group has lower power production and sagittal moments than either previously published age group. This strongly suggests that the biomechanical differences found in this study are evidence of functional deficiencies. Further research is needed to determine how these deficiencies progress with patient aging.

Results: 86 of the 91 patients randomized into the FAITH-2 pilot study were deemed eligible. There were no significant differences in patient-reported function or HRQL between the treatment groups at 12 months post-fracture. At the 6-and 9-month assessments, a potential benefit in hip function was seen in the cancellous screw group. In all treatment groups, participants reported lower function and HRQL at 12 months post-fracture as compared to their pre-injury assessment.Conclusions: Few differences were found in function and HRQL among the treatment groups in the FAITH-2 pilot study. Despite modern implants and vitamin D supplementation, neither function nor HRQL returns to baseline in this population. Additional effort s to improve the outcomes of these challenging injuries are still needed.