title: The effects of pubertal maturation and sex on biomechanics associated with risk of anterior cruciate ligament injury

authors: Butcher, Anna J.

subjects: ACL

abstract: Background: Anterior cruciate ligament (ACL) injuries account for 45% of internal knee injuries and are burdensome to society due to prolonged recovery times, substantial costs of care, functional movement impairments, and an increased risk of early-onset posttraumatic osteoarthritis. Non-contact ACL injury occurrence rates are increasing in young athletes; however, post-pubertal females are more susceptible to non-contact ACL injuries than their male counterparts or pre-pubertal individuals. Considerable growth and development occur during pubertal maturation, including to the musculoskeletal and neuromuscular systems, which contribute to changes in movement patterns during dynamic manoeuvres. These changes in movement patterns may be linked to non-contact ACL injuries, however, there remain gaps in our understanding of the potential changes in biomechanics associated with ACL injury risk across maturational phases and between sexes. It is possible that the greater non-contact ACL injury risk in post-pubertal females is linked with their biomechanical movement patterns during dynamic tasks. Using injury risk screening tasks that reflect sport and ACL injury risk manoeuvres could assist in informing preventative strategies.
Aim: The main aim of this PhD thesis was to investigate the effect of sex and maturation on biomechanics associated with risk of ACL injury in a series of dynamic tasks suitable for clinical use.
Methods: This thesis comprises two parts: first, a systematic literature review and pilot study; and second, the main experimental study. The systematic review identified studies examining ACL-related biomechanics during defined maturational phases in dynamic tasks. The pilot study tested 26 court and field sport athletes using 2D video analysis completing a maximal and normalised land-cut task and informed the methods for the main experimental study. For the main experimental study, test-retest reliability and cross-sectional experiments were conducted that involved four different single-leg drop-landing tasks: single-leg drop-land, single-leg drop-land and cut, single-leg rotating drop and hop, and single-leg drop and vertical hop. The reliability portion establishes the test-retest reliability of the biomechanical measures collected using 3D motion capture and force plates from 15 young individuals, whereas the cross-sectional portion compared the biomechanical and performance metrics of the four investigated single-leg tasks between males and females across three specific maturation stages from 69 individuals. 
Results: The systematic review included 18 studies examining 400 males, 1377 females, and 315 participants of undefined sex across various maturation stages. The methodological quality of most studies (n = 16) was considered good, and satisfactory for two. The most reported variables were knee abduction angle, knee abduction moment, knee flexion angle, and vertical ground reaction force (GRF). Knee abduction angles and moments and knee flexion angles were greater in late- and post-pubertal females than males and pre-pubertal females during both landing and cutting tasks. When normalised for body mass, ground reaction forces were generally greater in males compared to females overall and for less mature participants for both sexes. Overall quality of evidence was low or medium across the four biomechanical measures and findings were inconsistent between studies. Leap distances in the pilot study of the single-leg drop-land and cut task were significantly larger under a maximal than normalised to 150% of leg length condition (p < 0.001, ηp2 ≥ 0.417), with the maximal mean being 154.5 ± 24.7 cm (175.1 ± 18.6% leg length) and the normalised mean being 140.7 ± 19.7 cm (159.0 ± 5.8% of leg length). Regarding the reliability portion of the experimental study, all tasks demonstrated adequate [intraclass correlation coefficient (ICC) values > 0.50] levels of reliability for kinematic angles and moments aside from the metrics of peak extension moment, moment ranges, anterior/posterior GRF, and medial/lateral GRF; however, large coefficient of variation values were commonly observed, likely due to the small magnitude of measures. In the cross-sectional experiment, few significant differences were found between males and females within the ages of 7 and 20 years when not accounting for maturation stage, including at the knee. Most of the observed significant differences were found between maturation stages. In general, the pre-pubertal participants demonstrated higher relative vertical GRFs, more extended knee positions, and greater variability in coronal and transverse plane knee angles and moments. Post-pubertal males also occasionally exhibited some mechanics typically associated with increased risk of ACL injury. 
Discussion: The significant difference in single-leg drop-land and cut landing distances found in the pilot study between normalised and maximalised conditions imply that methods matter, whereby the normalised task may be better suited for heterogenous samples, but maximal for homogenous samples or pre-post study designs. Regarding the experimental study, it is possible that the movement pattern changes observed in the males were associated with improved performance or movement competence and not directly associated with an increased ACL injury risk. Additionally, although the results suggest that pre-pubertal participants exhibit biomechanics associated with ACL injury risk, it is relatively rare that ACL injuries occur in this population. A lack of exposure to more challenging sport and ACL injury specific manoeuvres, like the tasks used in the current research, likely contribute to their biomechanics differing from the more mature groups. Few differences in biomechanics were identified to indicate a decreased ACL injury risk with maturation, particularly in females. Hence, this lack of change combined with more frequent exposure to potentially injurious situations and greater sporting demand could contribute to the increased ACL injury occurrence in the late- to post-pubertal female population reported in the literature.
Conclusion: Overall, the lack of significant biomechanical differences found between sexes suggests there is no need to make screening tools or training interventions sex specific. As biomechanical factors associated with greater ACL injury risk were observed in the pre-pubertal groups, implementing screening and injury prevention in younger athletes (starting pre-puberty) could assist in development of safer landing strategies, proprioception, and neuromuscular control that significantly reduces the risk of ACL injuries as they mature.

text: The effects of pubertal maturation and sex on biomechanics associated with risk of anterior cruciate ligament injury Background: Anterior cruciate ligament (ACL) injuries account for 45% of internal knee injuries and are burdensome to society due to prolonged recovery times, substantial costs of care, functional movement impairments, and an increased risk of early-onset posttraumatic osteoarthritis. Non-contact ACL injury occurrence rates are increasing in young athletes; however, post-pubertal females are more susceptible to non-contact ACL injuries than their male counterparts or pre-pubertal individuals. Considerable growth and development occur during pubertal maturation, including to the musculoskeletal and neuromuscular systems, which contribute to changes in movement patterns during dynamic manoeuvres. These changes in movement patterns may be linked to non-contact ACL injuries, however, there remain gaps in our understanding of the potential changes in biomechanics associated with ACL injury risk across maturational phases and between sexes. It is possible that the greater non-contact ACL injury risk in post-pubertal females is linked with their biomechanical movement patterns during dynamic tasks. Using injury risk screening tasks that reflect sport and ACL injury risk manoeuvres could assist in informing preventative strategies.
Aim: The main aim of this PhD thesis was to investigate the effect of sex and maturation on biomechanics associated with risk of ACL injury in a series of dynamic tasks suitable for clinical use.
Methods: This thesis comprises two parts: first, a systematic literature review and pilot study; and second, the main experimental study. The systematic review identified studies examining ACL-related biomechanics during defined maturational phases in dynamic tasks. The pilot study tested 26 court and field sport athletes using 2D video analysis completing a maximal and normalised land-cut task and informed the methods for the main experimental study. For the main experimental study, test-retest reliability and cross-sectional experiments were conducted that involved four different single-leg drop-landing tasks: single-leg drop-land, single-leg drop-land and cut, single-leg rotating drop and hop, and single-leg drop and vertical hop. The reliability portion establishes the test-retest reliability of the biomechanical measures collected using 3D motion capture and force plates from 15 young individuals, whereas the cross-sectional portion compared the biomechanical and performance metrics of the four investigated single-leg tasks between males and females across three specific maturation stages from 69 individuals. 
Results: The systematic review included 18 studies examining 400 males, 1377 females, and 315 participants of undefined sex across various maturation stages. The methodological quality of most studies (n = 16) was considered good, and satisfactory for two. The most reported variables were knee abduction angle, knee abduction moment, knee flexion angle, and vertical ground reaction force (GRF). Knee abduction angles and moments and knee flexion angles were greater in late- and post-pubertal females than males and pre-pubertal females during both landing and cutting tasks. When normalised for body mass, ground reaction forces were generally greater in males compared to females overall and for less mature participants for both sexes. Overall quality of evidence was low or medium across the four biomechanical measures and findings were inconsistent between studies. Leap distances in the pilot study of the single-leg drop-land and cut task were significantly larger under a maximal than normalised to 150% of leg length condition (p < 0.001, ηp2 ≥ 0.417), with the maximal mean being 154.5 ± 24.7 cm (175.1 ± 18.6% leg length) and the normalised mean being 140.7 ± 19.7 cm (159.0 ± 5.8% of leg length). Regarding the reliability portion of the experimental study, all tasks demonstrated adequate [intraclass correlation coefficient (ICC) values > 0.50] levels of reliability for kinematic angles and moments aside from the metrics of peak extension moment, moment ranges, anterior/posterior GRF, and medial/lateral GRF; however, large coefficient of variation values were commonly observed, likely due to the small magnitude of measures. In the cross-sectional experiment, few significant differences were found between males and females within the ages of 7 and 20 years when not accounting for maturation stage, including at the knee. Most of the observed significant differences were found between maturation stages. In general, the pre-pubertal participants demonstrated higher relative vertical GRFs, more extended knee positions, and greater variability in coronal and transverse plane knee angles and moments. Post-pubertal males also occasionally exhibited some mechanics typically associated with increased risk of ACL injury. 
Discussion: The significant difference in single-leg drop-land and cut landing distances found in the pilot study between normalised and maximalised conditions imply that methods matter, whereby the normalised task may be better suited for heterogenous samples, but maximal for homogenous samples or pre-post study designs. Regarding the experimental study, it is possible that the movement pattern changes observed in the males were associated with improved performance or movement competence and not directly associated with an increased ACL injury risk. Additionally, although the results suggest that pre-pubertal participants exhibit biomechanics associated with ACL injury risk, it is relatively rare that ACL injuries occur in this population. A lack of exposure to more challenging sport and ACL injury specific manoeuvres, like the tasks used in the current research, likely contribute to their biomechanics differing from the more mature groups. Few differences in biomechanics were identified to indicate a decreased ACL injury risk with maturation, particularly in females. Hence, this lack of change combined with more frequent exposure to potentially injurious situations and greater sporting demand could contribute to the increased ACL injury occurrence in the late- to post-pubertal female population reported in the literature.
Conclusion: Overall, the lack of significant biomechanical differences found between sexes suggests there is no need to make screening tools or training interventions sex specific. As biomechanical factors associated with greater ACL injury risk were observed in the pre-pubertal groups, implementing screening and injury prevention in younger athletes (starting pre-puberty) could assist in development of safer landing strategies, proprioception, and neuromuscular control that significantly reduces the risk of ACL injuries as they mature.

year: 2025

title: Human,climatic and oceanographic influences on the marine environment of Pohnpei, Federated States of Micronesia

authors: Phillip, Naiten Bradley, Jr.

subjects: coral reefs

abstract: Coral reefs and marine resources are culturally, as well as economically, vital to Pohnpei, situated in the Federated States of Micronesia (FSM). Farming and fishing are the main sources of livelihood for most Pohnpeian communities.  Pohnpei has eleven Marine Protected Areas (MPAs) where nine are situated in the Pohnpei Island Lagoon and two MPAs on the outer low-lying atolls.  Like many other Pacific Island countries Pohnpei is on the verge of creating more MPAs.  However, the marine environment continues to be significantly threatened by human and natural influences.  The recognised threats are yet to be methodically investigated.

This thesis used a combination of sediment, coral, fish, climatic, and oceanographic data, and focused on the Pohnpei Lagoon, examining a range of natural and human issues in the marine environment both at the local level (focusing on that within the Pohnpei Lagoon) and regional level (focusing on the western Pacific region).

Evidence from historical, archaeological, and modern experience has influenced various marine impacts that have altered the coastline and the marine environment of the Pohnpei Lagoon.  Humans have greatly impacted on the coral diversity and fish populations in the Pohnpei Lagoon by over-fishing and contributing to accelerated sediment inputs. My study findings shows that that increased sea surface temperature (SST) caused by El Ni o events is not the only cause of coral bleaching, but also cooling of SST, and other human factors.  However, when corals bleach they recover by  symbiont shuffling .  This is an ingenious way in which corals host one or more varieties of their zooxanthelle (Symbiodinium symbiont clades) that are more tolerant of the stress caused by increased SST and human factors.

The recognised natural climatic variability, particularly the El Ni o/Southern Oscillation (ENSO), may pose a significant threat to the Pohnpei Lagoon. El Ni o events are associated with: a change in trade winds and stronger wind gusts attributed to typhoons; lower rainfall causing drought; a decrease in SST attributed to cooling of the marine environment; increase of salinity in marine estuaries affecting development and recruitment of marine species communities; and a steep fall in sea level exposing corals to other elements.  The various on-going human threats and El Ni o-like conditions have caused giant clams (Tridacna gigas) to become extinct, have endangered herbivorous fish populations, and caused coral bleaching by cooling of SST.  

Although high SSTs are normally blamed for coral bleaching, the last major bleaching event in Pohnpei (2002) was likely to be due to a reduction in salinity (freshwater runoff and lower sea level), and there has been strong recovery. However, decreasing water temperatures rather than increases of SSTs may contribute to coral bleaching in the Pohnpei Lagoon and the Micronesian region. The Micronesian region appears to have suffered relatively few episodes of regional coral bleaching events. This is due to the  Western Pacific Warm Pool  (WPWP) where sea surface temperatures exceed 29 C but also where various feedback mechanisms limit the maximum SSTs.

The management aims of Pohnpei's MPAs are to move forward, while still respecting traditional practices. However, a lack of scientific monitoring, technical support and funding restricts our understanding of human and natural influences on the existing MPAs and the Pohnpei Lagoon. With respect to our policy makers the findings of the present research have implications on the future work in Pohnpei's marine environment and for policy makers, to make more-informed decisions before establishing new MPAs.

My key recommendations were:  1.) Integrate coral and fish monitoring during and after El Ni o events to understand El Ni o effects on the Pohnpei environment.  2.)  Undertake herbivorous fish investigation into their populations inside and outside the MPAs.  3.) Do not cut down vegetation along coastline areas, as it prevents erosion 4.)  Investigate Symbiodinium coral clades in Pohnpei Lagoon and the outer low-lying atolls.

text: Human,climatic and oceanographic influences on the marine environment of Pohnpei, Federated States of Micronesia Coral reefs and marine resources are culturally, as well as economically, vital to Pohnpei, situated in the Federated States of Micronesia (FSM). Farming and fishing are the main sources of livelihood for most Pohnpeian communities.  Pohnpei has eleven Marine Protected Areas (MPAs) where nine are situated in the Pohnpei Island Lagoon and two MPAs on the outer low-lying atolls.  Like many other Pacific Island countries Pohnpei is on the verge of creating more MPAs.  However, the marine environment continues to be significantly threatened by human and natural influences.  The recognised threats are yet to be methodically investigated.

This thesis used a combination of sediment, coral, fish, climatic, and oceanographic data, and focused on the Pohnpei Lagoon, examining a range of natural and human issues in the marine environment both at the local level (focusing on that within the Pohnpei Lagoon) and regional level (focusing on the western Pacific region).

Evidence from historical, archaeological, and modern experience has influenced various marine impacts that have altered the coastline and the marine environment of the Pohnpei Lagoon.  Humans have greatly impacted on the coral diversity and fish populations in the Pohnpei Lagoon by over-fishing and contributing to accelerated sediment inputs. My study findings shows that that increased sea surface temperature (SST) caused by El Ni o events is not the only cause of coral bleaching, but also cooling of SST, and other human factors.  However, when corals bleach they recover by  symbiont shuffling .  This is an ingenious way in which corals host one or more varieties of their zooxanthelle (Symbiodinium symbiont clades) that are more tolerant of the stress caused by increased SST and human factors.

The recognised natural climatic variability, particularly the El Ni o/Southern Oscillation (ENSO), may pose a significant threat to the Pohnpei Lagoon. El Ni o events are associated with: a change in trade winds and stronger wind gusts attributed to typhoons; lower rainfall causing drought; a decrease in SST attributed to cooling of the marine environment; increase of salinity in marine estuaries affecting development and recruitment of marine species communities; and a steep fall in sea level exposing corals to other elements.  The various on-going human threats and El Ni o-like conditions have caused giant clams (Tridacna gigas) to become extinct, have endangered herbivorous fish populations, and caused coral bleaching by cooling of SST.  

Although high SSTs are normally blamed for coral bleaching, the last major bleaching event in Pohnpei (2002) was likely to be due to a reduction in salinity (freshwater runoff and lower sea level), and there has been strong recovery. However, decreasing water temperatures rather than increases of SSTs may contribute to coral bleaching in the Pohnpei Lagoon and the Micronesian region. The Micronesian region appears to have suffered relatively few episodes of regional coral bleaching events. This is due to the  Western Pacific Warm Pool  (WPWP) where sea surface temperatures exceed 29 C but also where various feedback mechanisms limit the maximum SSTs.

The management aims of Pohnpei's MPAs are to move forward, while still respecting traditional practices. However, a lack of scientific monitoring, technical support and funding restricts our understanding of human and natural influences on the existing MPAs and the Pohnpei Lagoon. With respect to our policy makers the findings of the present research have implications on the future work in Pohnpei's marine environment and for policy makers, to make more-informed decisions before establishing new MPAs.

My key recommendations were:  1.) Integrate coral and fish monitoring during and after El Ni o events to understand El Ni o effects on the Pohnpei environment.  2.)  Undertake herbivorous fish investigation into their populations inside and outside the MPAs.  3.) Do not cut down vegetation along coastline areas, as it prevents erosion 4.)  Investigate Symbiodinium coral clades in Pohnpei Lagoon and the outer low-lying atolls.

year: 2010

title: Viruses without vaccines, or valuing indigenous research? The tensions of introducing Western research assessment practices into an indigenous university

authors: Bruce Ferguson, Pip

abstract: Over my past twenty-five years of educational practice, I have striven to develop a better understanding of indigenous ways of being and doing (in New Zealand’s case, this involves the values and knowledge of Māori). I have done this by visiting and occasionally staying on marae (Māori gathering-places); by reading relevant literature; by engaging in conversations with knowledgeable scholars and by researching the impact of Western practices on indigenous peoples.

In 2003 I managed a research team for Te Wānanga o Aotearoa, a Māori tertiary institution with branches across the country. Our Tertiary Education Commission had just introduced a variation of the English RAE, called the Performance-Based Research Fund, through which government research funds would henceforth be distributed. In collaboration with Māori colleagues, we chose to enter this process, believing that Māori research would be recognised and funded by our participation.

While this proved to be the case, there were significant examples of values clashes, such as the requirement for people to ‘boast’ of their research achievements in a context where such boasting is anathema; to claim ownership of knowledge where tradition often indicates that knowledge is not the property of individuals; and worst, at one point I found myself accused by my Māori manager of introducing ‘viruses without vaccines’. By this he meant Westernised ideas and practices which appeared to be benevolent but in fact were toxic (the idea derives from white settlers who apparently gave native Americans blankets permeated with a virus, causing thousands to die).

In this paper I will explore tensions of operating cross-culturally, and whether/how we can protect people from unintended toxic consequences of intended benevolent actions.

text: Viruses without vaccines, or valuing indigenous research? The tensions of introducing Western research assessment practices into an indigenous university Over my past twenty-five years of educational practice, I have striven to develop a better understanding of indigenous ways of being and doing (in New Zealand’s case, this involves the values and knowledge of Māori). I have done this by visiting and occasionally staying on marae (Māori gathering-places); by reading relevant literature; by engaging in conversations with knowledgeable scholars and by researching the impact of Western practices on indigenous peoples.

In 2003 I managed a research team for Te Wānanga o Aotearoa, a Māori tertiary institution with branches across the country. Our Tertiary Education Commission had just introduced a variation of the English RAE, called the Performance-Based Research Fund, through which government research funds would henceforth be distributed. In collaboration with Māori colleagues, we chose to enter this process, believing that Māori research would be recognised and funded by our participation.

While this proved to be the case, there were significant examples of values clashes, such as the requirement for people to ‘boast’ of their research achievements in a context where such boasting is anathema; to claim ownership of knowledge where tradition often indicates that knowledge is not the property of individuals; and worst, at one point I found myself accused by my Māori manager of introducing ‘viruses without vaccines’. By this he meant Westernised ideas and practices which appeared to be benevolent but in fact were toxic (the idea derives from white settlers who apparently gave native Americans blankets permeated with a virus, causing thousands to die).

In this paper I will explore tensions of operating cross-culturally, and whether/how we can protect people from unintended toxic consequences of intended benevolent actions.

year: 2012