title: Kinematics of recreational male runners in "super", minimalist and habitual shoes

authors: Hébert-Losier, Kim

subjects: Science & Technology

abstract: We conducted an exploratory analysis to compare running kinematics of 16 male recreational runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin racing flat (FLAT), and their habitual (OWN) footwear. We also explored potential relationships between kinematic and physiological changes. Runners (age: 33 ± 12 y, V _O2peak: 55.2 ± 4.3 ml · kg−1·min−1) attended 3 sessions after completing an V _ O2peak test in which sagittal plane 3D kinematics at submaximal running speeds (60%, 70% and 80% ʋ V _ O2peak) were collected alongside economy measures. Kinematics were compared using notched boxplots, and between-shoe kinematic differences were plotted against between-shoe economy differences. Across intensities, VP4 involved longer flight times (6.7 to 10.0 ms) and lower stance hip range of motion (~3°), and greater vertical pelvis displacement than FLAT (~0.4 cm). Peak dorsiflexion angles (~2°), ankle range of motion (1.0° to 3.9°), and plantarflexion velocities (11.3 to 89.0 deg · sec−1) were greatest in FLAT and lowest in VP4. Foot-ground angles were smaller in FLAT (2.5° to 3.6°). Select kinematic variables were moderately related to economy, with higher step frequencies and longer step lengths in VP4 and FLAT associated with improved economy versus OWN. Footwear changes from OWN altered running kinematics. The most pronounced differences were observed in ankle, spatiotemporal, and foot-ground angle variables.

text: Kinematics of recreational male runners in "super", minimalist and habitual shoes We conducted an exploratory analysis to compare running kinematics of 16 male recreational runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin racing flat (FLAT), and their habitual (OWN) footwear. We also explored potential relationships between kinematic and physiological changes. Runners (age: 33 ± 12 y, V _O2peak: 55.2 ± 4.3 ml · kg−1·min−1) attended 3 sessions after completing an V _ O2peak test in which sagittal plane 3D kinematics at submaximal running speeds (60%, 70% and 80% ʋ V _ O2peak) were collected alongside economy measures. Kinematics were compared using notched boxplots, and between-shoe kinematic differences were plotted against between-shoe economy differences. Across intensities, VP4 involved longer flight times (6.7 to 10.0 ms) and lower stance hip range of motion (~3°), and greater vertical pelvis displacement than FLAT (~0.4 cm). Peak dorsiflexion angles (~2°), ankle range of motion (1.0° to 3.9°), and plantarflexion velocities (11.3 to 89.0 deg · sec−1) were greatest in FLAT and lowest in VP4. Foot-ground angles were smaller in FLAT (2.5° to 3.6°). Select kinematic variables were moderately related to economy, with higher step frequencies and longer step lengths in VP4 and FLAT associated with improved economy versus OWN. Footwear changes from OWN altered running kinematics. The most pronounced differences were observed in ankle, spatiotemporal, and foot-ground angle variables.

year: 2022-06-15

title: Ecological monitoring of artificial destratification effects in Lake Rotoehu: 2014-2015

authors: Tempero, Grant Wayne

abstract: Lake Rotoehu is a shallow (mean depth 8 m), polymictic eutrophic lake in the Rotorua lakes district. Catchment land use intensification has contributed to a decline in water quality and persistent cyanobacterial algal blooms for the past 20 years and combines with a background of nutrient-rich geothermal inflows. Two artificial mixing devices were deployed in Lake Rotoehu in the spring of 2012 by the Bay of Plenty Regional Council with the aim of preventing lake thermal stratification. They were previously operated over the summer-autumn periods of 2012-13 and 2013-14 and their effects were monitored on a monthly basis until June 2014. The devices force compressed air through a diffuser near the lake bottom, and into three large vertical cylinders. Buoyancy, caused by the rising bubbles, draws water from the bottom of the lake up through the vertical cylinders and directs it horizontally into the surface mixed layer (epilimnion). This causes mixing of thermally distinct layers of the water column, and is designed to inhibit stratification and prevent hypolimnetic deoxygenation. Results from previous monitoring indicate that the mixing devices produced a limited, localised mixing effect, but had no influence on whole lake ecology. With a view to improving performance, modifications, including channelling all air through a single mixing device and increasing compressor output, were effected in preparation for the 2014-15 summer-autumn seasons. The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct a monitoring programme to ascertain the effect of these modifications.
Three sites within Lake Rotoehu were sampled monthly at similar depths from October 2014 to May 2015. Sites 1 and 3 were located approximately 30 m from a mixing device and Site 2 acted as a control site as it was considered to be unaffected by the direct effects of the mixing. Zooplankton, phytoplankton and nutrient samples (total nitrogen, total phosphorus, nitrate, ammonium and dissolved phosphorus) were collected at two different depths (0.5 m and 9.0 m), at each site. In addition, CTD (conductivity, temperature, depth) vertical profiles were also taken at each site. Temperature data were also obtained from a fixed-sensor, high-frequency monitoring buoy deployed in the lake and used to determine lake stability.
The summer of 2014-15 produced conditions favourable for the formation of prolonged lake stratification. This resulted in a marked decline in water quality during January-May 2015 in comparison to the previous three years of monitoring data. Evidence of localised homogenisation by the mixing device of the dominant phytoplankton and zooplankton taxonomic groups demonstrated notable improvement in mixing device performance. Temperature profile data were more equivocal, with no clear observations of the effects of artificial mixing over an extended area of the lake. However, supplemental profiles taken from within the discharge plumes (approximately 30 m from the mixing device) demonstrated evidence of hypolimnetic water being discharged to the epilimnion.
It is concluded that the current design and configuration of the artificial mixing devices is effective in drawing water from the hypolimnion into the epilimnion. However, it appears that the thermal mass of Lake Rotoehu is too large for a single mixing device to overcome and there appears to be no substantial ecological benefit in continuing to operate the devices without substantial modification. If significant, sustained improvements in water quality are to be achieved using these devices, further capital investment will be required. Further research investigating the efficiency and area of influence of the mixing devices may help to improve their design and operation.

text: Ecological monitoring of artificial destratification effects in Lake Rotoehu: 2014-2015 Lake Rotoehu is a shallow (mean depth 8 m), polymictic eutrophic lake in the Rotorua lakes district. Catchment land use intensification has contributed to a decline in water quality and persistent cyanobacterial algal blooms for the past 20 years and combines with a background of nutrient-rich geothermal inflows. Two artificial mixing devices were deployed in Lake Rotoehu in the spring of 2012 by the Bay of Plenty Regional Council with the aim of preventing lake thermal stratification. They were previously operated over the summer-autumn periods of 2012-13 and 2013-14 and their effects were monitored on a monthly basis until June 2014. The devices force compressed air through a diffuser near the lake bottom, and into three large vertical cylinders. Buoyancy, caused by the rising bubbles, draws water from the bottom of the lake up through the vertical cylinders and directs it horizontally into the surface mixed layer (epilimnion). This causes mixing of thermally distinct layers of the water column, and is designed to inhibit stratification and prevent hypolimnetic deoxygenation. Results from previous monitoring indicate that the mixing devices produced a limited, localised mixing effect, but had no influence on whole lake ecology. With a view to improving performance, modifications, including channelling all air through a single mixing device and increasing compressor output, were effected in preparation for the 2014-15 summer-autumn seasons. The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct a monitoring programme to ascertain the effect of these modifications.
Three sites within Lake Rotoehu were sampled monthly at similar depths from October 2014 to May 2015. Sites 1 and 3 were located approximately 30 m from a mixing device and Site 2 acted as a control site as it was considered to be unaffected by the direct effects of the mixing. Zooplankton, phytoplankton and nutrient samples (total nitrogen, total phosphorus, nitrate, ammonium and dissolved phosphorus) were collected at two different depths (0.5 m and 9.0 m), at each site. In addition, CTD (conductivity, temperature, depth) vertical profiles were also taken at each site. Temperature data were also obtained from a fixed-sensor, high-frequency monitoring buoy deployed in the lake and used to determine lake stability.
The summer of 2014-15 produced conditions favourable for the formation of prolonged lake stratification. This resulted in a marked decline in water quality during January-May 2015 in comparison to the previous three years of monitoring data. Evidence of localised homogenisation by the mixing device of the dominant phytoplankton and zooplankton taxonomic groups demonstrated notable improvement in mixing device performance. Temperature profile data were more equivocal, with no clear observations of the effects of artificial mixing over an extended area of the lake. However, supplemental profiles taken from within the discharge plumes (approximately 30 m from the mixing device) demonstrated evidence of hypolimnetic water being discharged to the epilimnion.
It is concluded that the current design and configuration of the artificial mixing devices is effective in drawing water from the hypolimnion into the epilimnion. However, it appears that the thermal mass of Lake Rotoehu is too large for a single mixing device to overcome and there appears to be no substantial ecological benefit in continuing to operate the devices without substantial modification. If significant, sustained improvements in water quality are to be achieved using these devices, further capital investment will be required. Further research investigating the efficiency and area of influence of the mixing devices may help to improve their design and operation.

year: 2015

title: Empirical analysis of Pacific, Māori and ethnic pay gaps in New Zealand

authors: Cochrane, William

abstract: A descriptive profile of the four ethnic groups, by gender, is provided to illustrate the heterogeneities across populations in terms of a number of variables grouped into the following categories: individual characteristics, educational attainment, region, household and job-related characteristics. The main empirical analysis involves estimation of the statistical contribution of observed factors (within each of the aforementioned categories) towards explaining the ethnic pay gaps. As this research is primarily aimed as an input towards the Pacific Pay Gap Inquiry being conducted by the Human Rights Commission, we focus our summary of the key findings on the Pacific – European pay gap.
This includes variables on permanent contract status, an indicator if in part-time work, occupation, and industry. These results are therefore likely an indication of the strong role of occupational segregation in the labour market. An additional factor that had a relatively strong contribution to the pay gap, particularly for the Pacific – European female gap, was educational attainment. Overall, even after accounting for differences in job-related characteristics and educational attainment, amongst a number of other observed factors, it was still found that only 27 percent of the pay gap for Pacific males (relative to Europeans) could be explained; and the corresponding proportion for females was 39 percent. The remaining portion of the Pacific Pay Gap is likely to reflect a range of causes that cannot be quantified or disentangled in this analysis – such as not including other factors of importance as they weren’t observed in the data (for example, literacy proficiency or field of study for qualification attained); ethnic differences in preferences for non-wage components of the job; unconscious bias; and discrimination.

text: Empirical analysis of Pacific, Māori and ethnic pay gaps in New Zealand A descriptive profile of the four ethnic groups, by gender, is provided to illustrate the heterogeneities across populations in terms of a number of variables grouped into the following categories: individual characteristics, educational attainment, region, household and job-related characteristics. The main empirical analysis involves estimation of the statistical contribution of observed factors (within each of the aforementioned categories) towards explaining the ethnic pay gaps. As this research is primarily aimed as an input towards the Pacific Pay Gap Inquiry being conducted by the Human Rights Commission, we focus our summary of the key findings on the Pacific – European pay gap.
This includes variables on permanent contract status, an indicator if in part-time work, occupation, and industry. These results are therefore likely an indication of the strong role of occupational segregation in the labour market. An additional factor that had a relatively strong contribution to the pay gap, particularly for the Pacific – European female gap, was educational attainment. Overall, even after accounting for differences in job-related characteristics and educational attainment, amongst a number of other observed factors, it was still found that only 27 percent of the pay gap for Pacific males (relative to Europeans) could be explained; and the corresponding proportion for females was 39 percent. The remaining portion of the Pacific Pay Gap is likely to reflect a range of causes that cannot be quantified or disentangled in this analysis – such as not including other factors of importance as they weren’t observed in the data (for example, literacy proficiency or field of study for qualification attained); ethnic differences in preferences for non-wage components of the job; unconscious bias; and discrimination.

year: 2022-07