Humans, standing up about seven million years ago, have evolved independently by freeing their hands. However, many physical inconveniences, called negative legacies, are caused by the physical structure of modern humans. This review focuses on the structural causes of dystocia and how people respond to it.

Our previous cohort study used national data, and found a relationship between non-permanent employment and mental health deterioration during the COVID-19 induced state of emergency in Japan. However, non-response (approximately 22%) was a problem. Importantly, this non-response bias may limit the interpretability of our survey results. This study aimed to reveal the factors associated with non-response utilizing a follow-up survey based on our baseline data. We conducted a web-based survey of the working-age population in Japan carried once from March 26 to April 6, 2020, and again from June 26 to July 2, 2020. From a cohort of 3,001 Japanese workers, 650 and 2,351 did and did not drop out from the follow-up survey, respectively. We find that non-respondents had higher Center for Epidemiological Studies Depression Scale (CES-D) (non-respondents versus respondents: 18 [12-27] versus 15 [11-25], p < 0.001), lower sense of coherence (SOC) (non-respondents versus respondents: 51 [45-56] versus 52 [47-58], p < 0.001), and lower health-related quality of life (HRQOL) (non-respondents versus respondents: 0.867 [0.799-1.000] versus 0.895 [0.823-1.000], p < 0.001) scores. Logistic regression analyses revealed that the risk factors associated with causing non-response were younger age (odds ratio [OR] = 8.358), low level income (OR = 1.997), being single (OR = 1.435), not being head of household (OR = 1.377), and low SOC (OR = 1.310). Higher HRQOL scores were inversely associated with non-response (OR = 0.453). Thus, our findings raise the concern that non-response bias may underestimate mental health deterioration in non-permanent employees during our follow-up surveys. A repeated cross-sectional study may complement the assessment of prevalence of adverse mental health symptoms in Japan at a given time point during the COVID-19 pandemic.

Background and Purposes: When carrying a heavy load, people present compensatory postures with increased flexion angles of the head-neck, trunk joint, knee joint, and ankle joint and altered gait features. Adjusting the alignment of the prosthesis may reduce the impact of carrying a load on the gait of above-knee amputees; however, relevant studies have not been undertaken yet. This study investigated the gait differences in above-knee amputees when carrying weight on the trunk and carrying no weight. Materials and Methods: Eleven adults with above-knee amputation were enrolled. The alignment adjustment of the prosthetic knee joint in the sagittal plane was determined on the basis of the feelings of comfort and safety of each participant when walking with no load and with a load of 6, 11, and 16 kg on the front and back torso. Results: Changes in the gait variables when walking with no load and with different loads were analyzed. On the sound side, compared with the step length at the unloading condition, a shorter step length was observed only at the 11-kg front loading condition (p < 0.05). Moreover, compared with the stride length at the unloading condition, a shorter stride length was observed with a front load of 6, 11, and 16 kg (all p < 0.05). On the affected side, a shorter stride length was observed with a front load of 11 and 16 kg than with no load (both p < 0.05); moreover, a shorter stride length was observed with a front load of 11 and 16 kg than with no load and with a bilateral load of 6 kg (all p < 0.05). The alignment adjustments of the prosthetic knee joint highly correlated with the weight on the front (r = 0.85) and back (r = 0.91) trunk (both p < 0.05). Conclusion: Even after adjustment of the alignment of the prosthetic knee in the above-knee amputees, differences in several spatiotemporal gait variables were observed between the loading and unloading conditions. The currently available prosthetic knee does not allow for quick alignment adjustment to meet task demands; therefore, the results of this study can be used for developing lower limb prosthetic products that will enable users to handle heavy objects with ease in the future.