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Papers by Michael Lafiandra
Medicine and Science in Sports and Exercise, Mar 1, 2004
INTRODUCTION/PURPOSE: To determine the effects of backpack mass on the forces exerted by the back... more INTRODUCTION/PURPOSE: To determine the effects of backpack mass on the forces exerted by the backpack on the carrier and on the distribution of these forces between the upper back (including shoulders) and lower back (sacrum and iliac crest).METHODS: Eleven male volunteers (mean age 22.7 SEM 1.1 yr) walked on a level treadmill at 1.34 m.s(-1) carrying a backpack loaded to three different masses (13.6, 27.2, and 40.8 kg). The backpack's hip belt was connected to force transducers that measured the forces exerted on the lower back. The total force between the subject and backpack was determined from the backpack's mass and acceleration. Forces on the upper back were calculated as total force minus the forces exerted on the lower back.RESULTS: There was a significant effect of backpack mass on the vertical and anterior/posterior forces exerted on the upper and lower back, and on the total force exerted on the backpack center of mass. Regardless of mass, approximately 30% of the vertical force was borne by the lower back; the upper back and shoulders supported the remaining 70%; this is based on data averaged across the stride. Dimensionless analysis revealed peak forces on the upper and lower back increased proportionately to backpack mass whereas the peak forces exerted on the backpack COM increased disproportionately.CONCLUSIONS: The backpack exerts consistent anterior force on the lower back, which likely contributes to the occurrence of low-back pain associated with load carriage. Approximately 30% of the vertical force generated by the backpack can be transferred to the lower back by using an external frame backpack with a hip belt.
Medicine & Science in Sports & Exercise, 2004
To determine the effects of backpack mass on the forces exerted by the backpack on the carrier an... more To determine the effects of backpack mass on the forces exerted by the backpack on the carrier and on the distribution of these forces between the upper back (including shoulders) and lower back (sacrum and iliac crest). Eleven male volunteers (mean age 22.7 SEM 1.1 yr) walked on a level treadmill at 1.34 m.s(-1) carrying a backpack loaded to three different masses (13.6, 27.2, and 40.8 kg). The backpack's hip belt was connected to force transducers that measured the forces exerted on the lower back. The total force between the subject and backpack was determined from the backpack's mass and acceleration. Forces on the upper back were calculated as total force minus the forces exerted on the lower back. There was a significant effect of backpack mass on the vertical and anterior/posterior forces exerted on the upper and lower back, and on the total force exerted on the backpack center of mass. Regardless of mass, approximately 30% of the vertical force was borne by the lower back; the upper back and shoulders supported the remaining 70%; this is based on data averaged across the stride. Dimensionless analysis revealed peak forces on the upper and lower back increased proportionately to backpack mass whereas the peak forces exerted on the backpack COM increased disproportionately. The backpack exerts consistent anterior force on the lower back, which likely contributes to the occurrence of low-back pain associated with load carriage. Approximately 30% of the vertical force generated by the backpack can be transferred to the lower back by using an external frame backpack with a hip belt.
Medicine & Science in Sports & Exercise, 2004
Journal of Motor Behavior, 1999
An experiment was conducted in which volume of used oxygen per stride time and the total segmenta... more An experiment was conducted in which volume of used oxygen per stride time and the total segmental changes in kinetic energy generated per stride time, DeltaEk s-1, of 11 participants were determined on Day 1 for 7 treadmill running speeds. Gait transition speeds were determined on Day 2. Running metabolism and transition speed were predicted from the Day 1 mechanics of running expressed in Speed x DeltaEk s-1 coordinates. Predictions followed from the relation between 2 generalized quality ratios Qmetab, and Qmech, with numerator DeltaEk s-1. In Qmetab, the denominator was the volume of used oxygen per stride time; in Qmech, the denominator was the absolute regression constant from the linear dependency of DeltaEk s-1 on speed.
Human Movement Science, 2000
Journal of Biomechanics, Jan 4, 2003
The primary objective of this research was to determine changes in body and joint stiffness param... more The primary objective of this research was to determine changes in body and joint stiffness parameters and kinematics of the knee and body center of mass (COM), that result from wearing a backpack (BP) with a 40% body weight load at increasing speeds of walking. It was hypothesized that there would be speed and load-related increases in stiffness that would prevent significant deviations in the COM trajectory and in lower-extremity joint angles. Three independent biomechanical models employing kinematic data were used to estimate global lower-extremity stiffness, vertical stiffness and knee joint rotational stiffness in the sagittal plane during walking on a treadmill at speeds of 0.6-1.6 ms(-1) in 0.2 ms(-1) increments in BP and no backpack conditions. Kinematic data were collected using an Optotrak, three-dimensional motion analysis system. Knee angles and vertical excursion of the COM during the compression (loading phase) increased as a function of speed but not load. All three estimates of stiffness showed significant increases as a function of both speed and load. Significant interaction effects indicated a convergence of load-related stiffness values at lower speeds. Results suggested that increases in muscle-mediated stiffness are used to maintain a constant vertical excursion of the COM under load across the speeds tested, and thereby limit increases in metabolic cost that would occur if the COM would travel through greater vertical range of motion.
The purpose of this experiment was to determine the effects of walking speed and wearing a backpa... more The purpose of this experiment was to determine the effects of walking speed and wearing a backpack on trunk coordination and upper and lower body angular momentum, Twelve subjects (5 male, 7 female, mean age, yr: mean +/- SD = 26 +/- 7.1) walked on a treadmill at increasing speeds from 0.6 m(exp s-1) to 1.6 m(exp s-1) in 0.2 m(exp s-1) increments. Subjects walked wit a backpack (BP) containing 40% of their body mass and with no backpack (NBP). Peak pelvic and thoracic angular velocities were measured, and peak upper body and lower body angular momentum and the relative phase between the pelvis and thorax were calculated. A Repeated Measures ANOVA with two within-subject factors (load and speed) was used to compare the dependant variables, A significant main effect of BP condition was found in pelvic (p < 0.0001) and thoracic (p < 0.0001) angular velocity, upper (p < 0.0003) and lower (p < 0.0001) body angular momentum, and relative phase (p < 0.0014). In addition, a ...
To determine the effects of load carriage and walking speed on stride parameters and the coordina... more To determine the effects of load carriage and walking speed on stride parameters and the coordination of trunk movements, twelve subjects walked on a level treadmill at a range of walking speeds (0.6 m/s - 1.6 m/s) with and without a backpack containing 40% of their body mass. It was hypothesized that compared to unloaded walking load carriage decreases transverse pelvic and thoracic rotation, the mean relative phase between pelvic and thoracic rotations, and increases hip excursion. In addition, it was hypothesized that these changes would coincide with a decreased stride length and increase stride frequency. The findings supported the hypotheses. It was additionally hypothesized that the increased MOI of the upper body caused by the added mass of the backpack would result in an increase in upper body torque, an increase in lower body torque, and an increase in net body torque. Higher levels of upper body torque were observed in the backpack condition compared to the no backpack co...
The experiment evaluated the physiological, biomechanical, and maximal performance responses of 1... more The experiment evaluated the physiological, biomechanical, and maximal performance responses of 14 male soldiers wearing 2 current Army boots, 5 prototype Army boots, and 5 commercial hiking boots. Physiological evaluation determined the rate of oxygen consumption for carrying a 60-Ib backpack load while walking in each type of boot. Biomechanical analysis quantified gait, posture, and lower-extremity joint forces and torque. Maximal-speed runs with and without a 60-lb backpack were timed on both straight and zigzag 400 m grass courses. Comfort and functionality questionnaires were administered to the volunteers after they walked 6 miles at 3 mph over pavement and wooded trail in each boot-type; blisters and other foot trauma were assessed post-march. Based on their overall performance, the boots were ranked from best to worst as follows: (1) Salomon Adventure 9 Ultralight, (2) Raichle Highline,- (Tie for 3,4,5) Prototype 3, Prototype 4, Asolo Meridian, (6) Asolo AFX 535, (7) Protot...
Kevlar helmets provide the soldier with basic ballistic and impact protection. However, the helme... more Kevlar helmets provide the soldier with basic ballistic and impact protection. However, the helmet has recently become a mounting platform for devices such as night-vision goggles, drop down displays, weapon-aiming systems, etc. Although designed to enhance soldier performance, these systems increase the mass of the helmet and typically shift the position of the helmet's center of mass forward. The effects of changing the mass properties of the helmet on head and neck forces and moment on neck muscle activity and fatigue are well documented for aviators and soldiers in vehicles. No research to date has been focused on the effects of helmets of varying mass and mass distribution on head and neck forces and moments during a combat foot soldier's physical activities. Physical demands on the combat foot soldier are substantially different from those on aviator or soldiers in vehicles. Therefore, changing the mass properties of the helmet likely has different effects on combat fo...
The Board on Army Science and Technology has commissioned a committee on “Making the Soldier Deci... more The Board on Army Science and Technology has commissioned a committee on “Making the Soldier Decisive on Future Battlefields” with the overarching goal of identifying areas where our dismounted Soldiers have the potential for overmatch capability, particularly when operating in small units, and the technologies that will aide in realizing an overmatch. To supplement this effort, this report discusses five high-potential areas of technology from the realm of the human dimension, considering the integrative nature between the Soldier and the systems with which they interact. We first discuss technologies that show promise within the realm of training, by helping to better prepare the individual Soldier for potentially volatile situations, followed by a description of technologies for predicting a user’s intent via physiological assessment techniques. Then we discuss improved human-robot interactions gained through recent advances in control design, yielding increased throughput of the...
Previously, an external-frame backpack device (35 kg) was fabricated allowing for the placement o... more Previously, an external-frame backpack device (35 kg) was fabricated allowing for the placement of a 24.9-kg lead brick load in nine different positions. The purpose of this report was to determine the moment of inertia (MOI) of the backpack for the nine load positions relative to: the backpack's center of mass (COM); reference axes originating on the backpack frame; the COM for the human torso and backpack combined; and the COM for the human body and backpack combined. For the backpack about its COM, the lowest MOI values were found when the COM was located intermediate/central and intermediate/close relative to the load-carrier's trunk. For the backpack relative to the reference axes, the lowest MOI values were found when the COM was located low/central and low/close to the trunk. For the torso and backpack system and for the body and backpack system, the lowest MOI values were found when the COM relative to the trunk was in the intermediate/close or high/close position an...
Medicine and Science in Sports and Exercise, Mar 1, 2004
INTRODUCTION/PURPOSE: To determine the effects of backpack mass on the forces exerted by the back... more INTRODUCTION/PURPOSE: To determine the effects of backpack mass on the forces exerted by the backpack on the carrier and on the distribution of these forces between the upper back (including shoulders) and lower back (sacrum and iliac crest).METHODS: Eleven male volunteers (mean age 22.7 SEM 1.1 yr) walked on a level treadmill at 1.34 m.s(-1) carrying a backpack loaded to three different masses (13.6, 27.2, and 40.8 kg). The backpack's hip belt was connected to force transducers that measured the forces exerted on the lower back. The total force between the subject and backpack was determined from the backpack's mass and acceleration. Forces on the upper back were calculated as total force minus the forces exerted on the lower back.RESULTS: There was a significant effect of backpack mass on the vertical and anterior/posterior forces exerted on the upper and lower back, and on the total force exerted on the backpack center of mass. Regardless of mass, approximately 30% of the vertical force was borne by the lower back; the upper back and shoulders supported the remaining 70%; this is based on data averaged across the stride. Dimensionless analysis revealed peak forces on the upper and lower back increased proportionately to backpack mass whereas the peak forces exerted on the backpack COM increased disproportionately.CONCLUSIONS: The backpack exerts consistent anterior force on the lower back, which likely contributes to the occurrence of low-back pain associated with load carriage. Approximately 30% of the vertical force generated by the backpack can be transferred to the lower back by using an external frame backpack with a hip belt.
Medicine & Science in Sports & Exercise, 2004
To determine the effects of backpack mass on the forces exerted by the backpack on the carrier an... more To determine the effects of backpack mass on the forces exerted by the backpack on the carrier and on the distribution of these forces between the upper back (including shoulders) and lower back (sacrum and iliac crest). Eleven male volunteers (mean age 22.7 SEM 1.1 yr) walked on a level treadmill at 1.34 m.s(-1) carrying a backpack loaded to three different masses (13.6, 27.2, and 40.8 kg). The backpack&amp;#39;s hip belt was connected to force transducers that measured the forces exerted on the lower back. The total force between the subject and backpack was determined from the backpack&amp;#39;s mass and acceleration. Forces on the upper back were calculated as total force minus the forces exerted on the lower back. There was a significant effect of backpack mass on the vertical and anterior/posterior forces exerted on the upper and lower back, and on the total force exerted on the backpack center of mass. Regardless of mass, approximately 30% of the vertical force was borne by the lower back; the upper back and shoulders supported the remaining 70%; this is based on data averaged across the stride. Dimensionless analysis revealed peak forces on the upper and lower back increased proportionately to backpack mass whereas the peak forces exerted on the backpack COM increased disproportionately. The backpack exerts consistent anterior force on the lower back, which likely contributes to the occurrence of low-back pain associated with load carriage. Approximately 30% of the vertical force generated by the backpack can be transferred to the lower back by using an external frame backpack with a hip belt.
Medicine & Science in Sports & Exercise, 2004
Journal of Motor Behavior, 1999
An experiment was conducted in which volume of used oxygen per stride time and the total segmenta... more An experiment was conducted in which volume of used oxygen per stride time and the total segmental changes in kinetic energy generated per stride time, DeltaEk s-1, of 11 participants were determined on Day 1 for 7 treadmill running speeds. Gait transition speeds were determined on Day 2. Running metabolism and transition speed were predicted from the Day 1 mechanics of running expressed in Speed x DeltaEk s-1 coordinates. Predictions followed from the relation between 2 generalized quality ratios Qmetab, and Qmech, with numerator DeltaEk s-1. In Qmetab, the denominator was the volume of used oxygen per stride time; in Qmech, the denominator was the absolute regression constant from the linear dependency of DeltaEk s-1 on speed.
Human Movement Science, 2000
Journal of Biomechanics, Jan 4, 2003
The primary objective of this research was to determine changes in body and joint stiffness param... more The primary objective of this research was to determine changes in body and joint stiffness parameters and kinematics of the knee and body center of mass (COM), that result from wearing a backpack (BP) with a 40% body weight load at increasing speeds of walking. It was hypothesized that there would be speed and load-related increases in stiffness that would prevent significant deviations in the COM trajectory and in lower-extremity joint angles. Three independent biomechanical models employing kinematic data were used to estimate global lower-extremity stiffness, vertical stiffness and knee joint rotational stiffness in the sagittal plane during walking on a treadmill at speeds of 0.6-1.6 ms(-1) in 0.2 ms(-1) increments in BP and no backpack conditions. Kinematic data were collected using an Optotrak, three-dimensional motion analysis system. Knee angles and vertical excursion of the COM during the compression (loading phase) increased as a function of speed but not load. All three estimates of stiffness showed significant increases as a function of both speed and load. Significant interaction effects indicated a convergence of load-related stiffness values at lower speeds. Results suggested that increases in muscle-mediated stiffness are used to maintain a constant vertical excursion of the COM under load across the speeds tested, and thereby limit increases in metabolic cost that would occur if the COM would travel through greater vertical range of motion.
The purpose of this experiment was to determine the effects of walking speed and wearing a backpa... more The purpose of this experiment was to determine the effects of walking speed and wearing a backpack on trunk coordination and upper and lower body angular momentum, Twelve subjects (5 male, 7 female, mean age, yr: mean +/- SD = 26 +/- 7.1) walked on a treadmill at increasing speeds from 0.6 m(exp s-1) to 1.6 m(exp s-1) in 0.2 m(exp s-1) increments. Subjects walked wit a backpack (BP) containing 40% of their body mass and with no backpack (NBP). Peak pelvic and thoracic angular velocities were measured, and peak upper body and lower body angular momentum and the relative phase between the pelvis and thorax were calculated. A Repeated Measures ANOVA with two within-subject factors (load and speed) was used to compare the dependant variables, A significant main effect of BP condition was found in pelvic (p < 0.0001) and thoracic (p < 0.0001) angular velocity, upper (p < 0.0003) and lower (p < 0.0001) body angular momentum, and relative phase (p < 0.0014). In addition, a ...
To determine the effects of load carriage and walking speed on stride parameters and the coordina... more To determine the effects of load carriage and walking speed on stride parameters and the coordination of trunk movements, twelve subjects walked on a level treadmill at a range of walking speeds (0.6 m/s - 1.6 m/s) with and without a backpack containing 40% of their body mass. It was hypothesized that compared to unloaded walking load carriage decreases transverse pelvic and thoracic rotation, the mean relative phase between pelvic and thoracic rotations, and increases hip excursion. In addition, it was hypothesized that these changes would coincide with a decreased stride length and increase stride frequency. The findings supported the hypotheses. It was additionally hypothesized that the increased MOI of the upper body caused by the added mass of the backpack would result in an increase in upper body torque, an increase in lower body torque, and an increase in net body torque. Higher levels of upper body torque were observed in the backpack condition compared to the no backpack co...
The experiment evaluated the physiological, biomechanical, and maximal performance responses of 1... more The experiment evaluated the physiological, biomechanical, and maximal performance responses of 14 male soldiers wearing 2 current Army boots, 5 prototype Army boots, and 5 commercial hiking boots. Physiological evaluation determined the rate of oxygen consumption for carrying a 60-Ib backpack load while walking in each type of boot. Biomechanical analysis quantified gait, posture, and lower-extremity joint forces and torque. Maximal-speed runs with and without a 60-lb backpack were timed on both straight and zigzag 400 m grass courses. Comfort and functionality questionnaires were administered to the volunteers after they walked 6 miles at 3 mph over pavement and wooded trail in each boot-type; blisters and other foot trauma were assessed post-march. Based on their overall performance, the boots were ranked from best to worst as follows: (1) Salomon Adventure 9 Ultralight, (2) Raichle Highline,- (Tie for 3,4,5) Prototype 3, Prototype 4, Asolo Meridian, (6) Asolo AFX 535, (7) Protot...
Kevlar helmets provide the soldier with basic ballistic and impact protection. However, the helme... more Kevlar helmets provide the soldier with basic ballistic and impact protection. However, the helmet has recently become a mounting platform for devices such as night-vision goggles, drop down displays, weapon-aiming systems, etc. Although designed to enhance soldier performance, these systems increase the mass of the helmet and typically shift the position of the helmet's center of mass forward. The effects of changing the mass properties of the helmet on head and neck forces and moment on neck muscle activity and fatigue are well documented for aviators and soldiers in vehicles. No research to date has been focused on the effects of helmets of varying mass and mass distribution on head and neck forces and moments during a combat foot soldier's physical activities. Physical demands on the combat foot soldier are substantially different from those on aviator or soldiers in vehicles. Therefore, changing the mass properties of the helmet likely has different effects on combat fo...
The Board on Army Science and Technology has commissioned a committee on “Making the Soldier Deci... more The Board on Army Science and Technology has commissioned a committee on “Making the Soldier Decisive on Future Battlefields” with the overarching goal of identifying areas where our dismounted Soldiers have the potential for overmatch capability, particularly when operating in small units, and the technologies that will aide in realizing an overmatch. To supplement this effort, this report discusses five high-potential areas of technology from the realm of the human dimension, considering the integrative nature between the Soldier and the systems with which they interact. We first discuss technologies that show promise within the realm of training, by helping to better prepare the individual Soldier for potentially volatile situations, followed by a description of technologies for predicting a user’s intent via physiological assessment techniques. Then we discuss improved human-robot interactions gained through recent advances in control design, yielding increased throughput of the...
Previously, an external-frame backpack device (35 kg) was fabricated allowing for the placement o... more Previously, an external-frame backpack device (35 kg) was fabricated allowing for the placement of a 24.9-kg lead brick load in nine different positions. The purpose of this report was to determine the moment of inertia (MOI) of the backpack for the nine load positions relative to: the backpack's center of mass (COM); reference axes originating on the backpack frame; the COM for the human torso and backpack combined; and the COM for the human body and backpack combined. For the backpack about its COM, the lowest MOI values were found when the COM was located intermediate/central and intermediate/close relative to the load-carrier's trunk. For the backpack relative to the reference axes, the lowest MOI values were found when the COM was located low/central and low/close to the trunk. For the torso and backpack system and for the body and backpack system, the lowest MOI values were found when the COM relative to the trunk was in the intermediate/close or high/close position an...