title: Kinematics of Usain Bolt’s maximal sprint velocity

authors: Čoh, Milan

subjects: Science & Technology

abstract: This study investigated the maximal sprint velocity kinematics of the fastest 100 m sprinter, Usain Bolt. Two high-speed video cameras recorded kinematics from 60 to 90 m during the men 100 m final at the IAAF World Challenge Zagreb 2011, Croatia. Despite a relatively slow reaction time (194 ms), Bolt won in 9.85 s (mean velocity:10.15 m/s). His fastest 20-m section velocity was 12.14 m/s, reached between 70 and 90 m, by 2.70-m long strides and 4.36 strides/s frequency. At the maximal velocity, his contact and flight times were 86 and 145 ms, respectively, and vertical ground reaction force generated equalled 4.2 times his body weight (3932 N). The braking and propulsion phase represented 37% and 63% of ground contact, respectively, with his centre of mass (CoM) exhibiting minor reductions in horizontal velocity (2.7%) and minimal vertical displacement (4.9 cm). Emerged Bolt’s maximal sprint velocity and international predominance from coordinated motor abilities, power generation capacities, and effective technique. This study confirms that his maximal velocity was achieved by means of relatively long strides, minimal braking phase, high vertical ground reaction force, and minimal vertical displacement of CoM. This study is the first in-depth biomechanical analysis of Bolt’s maximal sprinting velocity with the segmental reconstruction.

text: Kinematics of Usain Bolt’s maximal sprint velocity This study investigated the maximal sprint velocity kinematics of the fastest 100 m sprinter, Usain Bolt. Two high-speed video cameras recorded kinematics from 60 to 90 m during the men 100 m final at the IAAF World Challenge Zagreb 2011, Croatia. Despite a relatively slow reaction time (194 ms), Bolt won in 9.85 s (mean velocity:10.15 m/s). His fastest 20-m section velocity was 12.14 m/s, reached between 70 and 90 m, by 2.70-m long strides and 4.36 strides/s frequency. At the maximal velocity, his contact and flight times were 86 and 145 ms, respectively, and vertical ground reaction force generated equalled 4.2 times his body weight (3932 N). The braking and propulsion phase represented 37% and 63% of ground contact, respectively, with his centre of mass (CoM) exhibiting minor reductions in horizontal velocity (2.7%) and minimal vertical displacement (4.9 cm). Emerged Bolt’s maximal sprint velocity and international predominance from coordinated motor abilities, power generation capacities, and effective technique. This study confirms that his maximal velocity was achieved by means of relatively long strides, minimal braking phase, high vertical ground reaction force, and minimal vertical displacement of CoM. This study is the first in-depth biomechanical analysis of Bolt’s maximal sprinting velocity with the segmental reconstruction.

year: 2018

title: Tree species sorting along temperature gradients: How do frost-resistant traits influence competitive ability in the forest environment?

authors: FitzPatrick, Dominic Luke

subjects: forest ecology

abstract: To thrive in the forest environment a species must be able to pass each of three filters: first it must reach a site (the historical filter), then it must be able to tolerate the physical environment (the physiological filter) and finally it must be able to cope with biotic interactions at the site (the biotic filter). This thesis comprises of two complementary studies that explore the role temperature gradients play in determining a species ability to pass the physiological and biotic filters of a temperate rainforest. These studies were conducted using the seedlings of New Zealand warm- and cool- temperate tree species. The first study addresses how the trade-off in shade tolerance vs. growth rate found throughout closed-canopy forests changes from warm-temperate to cool-temperate environments using a transplant experiment. The second study aims to determine the implications of climate-related variation in xylem anatomy for morphological and physiological traits related to competitive ability. Warm-temperate species were found to be both faster-growing and more shade-tolerant than the cool-temperate species, indicating that cold resistant traits reduce competitive ability in warmer environments. This was supported by findings that the warm-temperate species had more conductive xylem and correspondingly higher levels of leaf area deployed than the cool species, indicating that cold resistance indirectly reduces the leafiness of a species. These cool-temperate species with less leaf surface area are less effective at intercepting light, resulting in lower growth rates and reduced shade tolerance which are important components of competitive ability in tree species. This may explain their absence from warmer forest environments, and their restriction to colder environments.

text: Tree species sorting along temperature gradients: How do frost-resistant traits influence competitive ability in the forest environment? To thrive in the forest environment a species must be able to pass each of three filters: first it must reach a site (the historical filter), then it must be able to tolerate the physical environment (the physiological filter) and finally it must be able to cope with biotic interactions at the site (the biotic filter). This thesis comprises of two complementary studies that explore the role temperature gradients play in determining a species ability to pass the physiological and biotic filters of a temperate rainforest. These studies were conducted using the seedlings of New Zealand warm- and cool- temperate tree species. The first study addresses how the trade-off in shade tolerance vs. growth rate found throughout closed-canopy forests changes from warm-temperate to cool-temperate environments using a transplant experiment. The second study aims to determine the implications of climate-related variation in xylem anatomy for morphological and physiological traits related to competitive ability. Warm-temperate species were found to be both faster-growing and more shade-tolerant than the cool-temperate species, indicating that cold resistant traits reduce competitive ability in warmer environments. This was supported by findings that the warm-temperate species had more conductive xylem and correspondingly higher levels of leaf area deployed than the cool species, indicating that cold resistance indirectly reduces the leafiness of a species. These cool-temperate species with less leaf surface area are less effective at intercepting light, resulting in lower growth rates and reduced shade tolerance which are important components of competitive ability in tree species. This may explain their absence from warmer forest environments, and their restriction to colder environments.

year: 2015

title: Hei Āwhina Mātua: A kaupapa Māori response to behaviour

authors: Berryman, Mere

abstract: Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

text: Hei Āwhina Mātua: A kaupapa Māori response to behaviour Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

year: 2015