The most important factor in producing clubhead speed in golf

Substantial experiential research into x-factor, and to a lesser extent crunch-factor has been undertaken with the aim of increasing clubhead speed. However, a direct comparison of the golf swing kinematics associated with each ‘factor’ has not, and possible differences when using a driver compared to an iron. Fifteen low handicap male golfers who displayed a modern swing had their golf swing kinematic data measured when hitting their own driver and five-iron, using a 10-camera motion analysis system operating at 250 Hz. Clubhead speed was collected using a validated launch monitor. No between-club differences in x-factor and crunch-factor existed. Correlation analyses revealed within-club segment (trunk and lower trunk) interaction was different for the driver, compared to the five-iron, and that a greater number of kinematic variables associated with x-factor, compared to crunch-factor were shown to be correlated with faster clubhead speeds. This was further explained in the five-iron regression model, where a significant amount of variance in clubhead speed was associated with increased lower trunk x-factor stretch, and reduced trunk lateral bending. Given that greens in regulation was shown to be the strongest correlated variable with PGA Tour earnings (1990-2004), the findings suggests a link to player performance for approach shots. These findings support other empiric research into the importance of x-factor as well as anecdotal evidence on how crunch-factor can negatively affect clubhead speed

The impact of tool selection on back and wrist injury risk in tying steel reinforcement bars: a single case experiment

The paper explores the risk of work-related musculoskeletal injury in tying steel reinforcement bars. Three tools are compared to determine the extent to which ergonomic tools can reduce the risk of injury to the back and wrist in steel-tying. A whole body system of wearable sensors was used to measure biomechanical risk in tying. Three tools were assessed to determine their impact on the risk of work-related musculoskeletal injury when used at different heights. These were: a conventional pincer-cutting tool; a power-driven tying tool, and a long handled stapler tool. No tool was found to work best in all situations. The long handled stapler tool significantly reduced trunk inclination when used from ground to shoulder height, but produced higher trunk extension (backward bending) when used above shoulder height. The power tying tool did not reduce the need to bend when working at lower work heights. The power-tying tool produced significantly lower peak wrist flexion values compared to the conventional pincer-cutter tool at all work heights except overhead. The power tying tool involved significantly lower levels of wrist rotation than the conventional pincer-cutter tool at all work heights above knee level. Many assessments of ergonomic risk factors in construction rely on observational methods. The use of small, lightweight wearable sensors permits the objective measurement of biomechanical risk factors for work-related musculoskeletal injury, as well as providing objective performance data that can be used in the design and selection of task-specific tools. Our analysis of work by height also provides insight into the way in which risk factors and reduction opportunities afforded by different tools vary depending on the height at which work is to be performed

The impact of tool selection on back and wrist injury risk in tying steel reinforcement bars: a single case experiment

The paper explores the risk of work-related musculoskeletal injury in tying steel reinforcement bars. Three tools are compared to determine the extent to which ergonomic tools can reduce the risk of injury to the back and wrist in steel-tying. A whole body system of wearable sensors was used to measure biomechanical risk in tying. Three tools were assessed to determine their impact on the risk of work-related musculoskeletal injury when used at different heights. These were: a conventional pincer-cutting tool; a power-driven tying tool, and a long handled stapler tool. No tool was found to work best in all situations. The long handled stapler tool significantly reduced trunk inclination when used from ground to shoulder height, but produced higher trunk extension (backward bending) when used above shoulder height. The power tying tool did not reduce the need to bend when working at lower work heights. The power-tying tool produced significantly lower peak wrist flexion values compared to the conventional pincer-cutter tool at all work heights except overhead. The power tying tool involved significantly lower levels of wrist rotation than the conventional pincer-cutter tool at all work heights above knee level. Many assessments of ergonomic risk factors in construction rely on observational methods. The use of small, lightweight wearable sensors permits the objective measurement of biomechanical risk factors for work-related musculoskeletal injury, as well as providing objective performance data that can be used in the design and selection of task-specific tools. Our analysis of work by height also provides insight into the way in which risk factors and reduction opportunities afforded by different tools vary depending on the height at which work is to be performed

Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

Effects of Slips and Trips on Resultant Lumbar Kinematics, Lumbar Muscle Activity and Low-Back Loads

Slips, trips, and falls (STFs) represent one of the leading causes of occupational injuries and fatalities. In particular, many prior reports have linked STFs with the onset of low-back disorders, which, depending on the severity of the incident, can leave the worker physically limited both in the workplace and at home. In contrast, the incidence and outcomes of loads acting on the low back due to a slip and trip that does not lead to a fall (i.e., slip/trip without fall: STWF) remain only marginally investigated to date. To address this research deficit, this quantitative study was designed to explore selected physiological outcomes of STWFs. In terms of methodology, participants completed several walking trials during which two unexpected perturbations involving a slip and trip were introduced (a harness prevented a fall). A biomechanical model developed using the AnyBody modeling software yielded trunk kinematics and muscle geometry. These outputs - along with the electromyography of fourteen lumbar flexor and extensor muscles - were employed as input data for our 3D, dynamic, EMG-based lumbar spine model. Results of (a) lumbar kinematics (range of the motion of the trunk relative to the pelvis), (b) lumbar muscle activity, (c) lumbosacral reaction forces, and (d) moments all indicated more than a two-fold increase during the slip and trip trials compared to normal walking. Specifically, reported values for the slip trial were (a) 45°, (b) 0.694, (c) 2939 N, and (d) 52 Nm; Reported values for the trip trial were (a) 42°, (b) 0.691, (c) 2898 N, and (d) 50 Nm; and the analogous figures for normal walking were (a) 19°,(b) 0.195, (c) 1174 N, and (d) 16 Nm. Findings from this study can be used to develop interventions to avoid such incidents; for example, to determine specific training parameters (e.g., frequency, duration, and intensity) to optimize a developed intervention’s effectiveness. Such approaches may lead to the control of specific mechanisms involved with lowback disorders consequent to a slip or trip, and potentially reduce the risk for slip- and trip-related injuries

LOWER BACK BIOMECHANICS AT NON-CHRONIC STAGE OF LOW BACK PAIN

Prior studies have reported differences in lower back biomechanics during activities of daily living between individuals with and without chronic low back pain (LBP). Nevertheless, the literature on lower back biomechanics of patients with non-chronic LBP is scant. Therefore, the objective of this study, as the first step towards future prospective studies, was to investigate the lower back biomechanics in patients with non-chronic LBP. Case-control studies were conducted wherein measures of lumbo-pelvic coordination during bending and return tasks as well as measures of mechanical demand on the lower back during lifting tasks in the sagittal plane were investigated between patients with non-chronic LBP and matched asymptomatic individuals. Patients were enrolled into the study at the non-chronic stage of their LBP. We found distinct difference in measures of lumbo-pelvic coordination as well as mechanical demands on the lower back between patients with non-chronic LBP and controls. Reduced lumbar range of flexion and slower task pace as well as the more in-phase and less variable lumbo-pelvic coordination observed in patients with non-chronic low back pain, may be the result of a neuromuscular adaptation to reduce the forces and deformation in the lower back tissues and avoid pain aggravation. Such a neuromuscular adaptation, however, resulted in a larger shearing demand on the lower back. Persistent abnormal lumbo-pelvic coordination might play a role in transition to chronic stage or recurrence of LBP. However, such inferences need to be further investigated using prospective studies as well as clinical trials involving a combination of physical and psychological treatments aimed at correction of lumbo-pelvic coordination

Spine Lifting Biomechanics Between Varying Occupational Activity Levels And Recreational Physical Activity Levels

Background: Moderate to vigorous physical activity as the optimum movement patterns for health have continued to be the dominant focus of health and fitness research. Yet, emerging evidence of deleterious, adverse health effects of prolonged inactivity, independent of regular physical activity, presents a new element to establishing the ideal model of movement patterns for health. The musculoskeletal trunk of the body becomes unbalanced as a result of prolonged inactivity, and a biomechanical analysis can help to identify high-risk loading behavior associated with these unbalances. Moreover, poor spine biomechanics can indicate a need for adjustment to present recommendations for optimum movement patterns. Some research of spine biomechanics associated with sedentary occupation or lifestyle exists. However, up to the author’s knowledge, no research exists on sedentary lifestyle independent of recreational physical fitness in respect to spine biomechanics. Purpose: The purpose of this study was to identify biomechanical patterns and significant differences in lifting biomechanics among individuals who are occupationally inactive and active, as well as recreationally active and inactive. Methods: Participants were divided into four groups using the Cambridge EPIC (European Prospective Investigation into Cancer and Nutrition)-Norfolk Physical Activity Questionnaire (EPAQ2): inactive, moderately inactive, moderately active, and active. A total of 23 participants completed the protocol. Spine kinematics of lifting was collected through VICON motion capture system. Additionally, ground reaction forces (GRF) and ground reaction moments (GRM) were collected by forceplate. Kinematic dependent variables were calculated from joint angle curves of trunk segments; included was maximum angular displacement of the middle trunk and lower trunk. Kinetic dependent variables were calculated from the GRF and GRM data, including maximum anterior excursion, maximum anterior velocity, and sway area of the center of pressure (COP) trajectories. Difference of each dependent variable between groups was detected by 1-way ANOVA. When difference existed, post-hoc pair-wise comparisons were conducted and Bonferroni correction was applied to minimize family-wise errors. The significance level was set at α = 0.05. Hypothesis: Participants who maintain an inactive lifestyle, regardless of recreational physical activity, will exhibit significantly different lifting biomechanics when compared to the lifting biomechanics of an active population performing the same lifting tasks. Results: Results indicated a statistically significant difference in flexion range of motion for the inactive group compared to all other groups (p=0.014). The inactive group had a significantly lower degree of flexion range of motion. Joint kinematic data indicated little difference between groups for the reaching phase and lift up phase of straight leg lifts. For bent leg lifts, the active population had significantly greater middle trunk flexion displacement during the reaching phase (p=0.005) and lifting phase (p=0.023) of bent leg lifts. No other significant differences existed between the other groups. Analysis of force platform data produced no significant differences between groups. Percent flexion range of motion was significantly different for the active population during the bent leg reaching phase and lifting phase compared with all other groups. The active population used a much larger degree of their total flexion range of motion to reach and lift up the box from the ground. Discussion: The current study aimed to investigate the effect of a largely inactive lifestyle, independent of regular participation in planned physical exercise, on spine kinematics, center of pressure, and range of motion. Results show evidence of a tendency for greater range of motion and greater flexion displacement of the active sample. Although not statistically significant, the inactive sample findings unexpectedly indicated a tendency for increased flexion displacement compared with the moderately active and moderately inactive groups. The moderately inactive group did not have any significant differences when compare to the moderately active group, which did not support the original hypothesis. However, the inactive group had poorer range of motion compared with all other groups, which supports the initial predictions. In summary, the inactive group presented some evidence of poor biomechanics. The active group shosigns of increased range of motion and flexibility. Finally, the moderately active and moderately inactive groups were very similar among all calculated variables. These findings support previous evidence of regular activity improving range of motion and flexibility. Occupational inactivity coupled with regular recreational activity appears to reduce the risk of developing poor lifting biomechanics

Biomechanics of Leaning and Downward Reaching Tasks in Young and Older Women.

Stooping crouching or kneeling (SCK) difficulty is prevalent among older adults yet few studies have explored the mechanisms underlying downward reaching and pick-up difficulty. During targeted movements tradeoffs are expected between the speed and accuracy of center of pressure (COP) movements as balance is maintained. Thus, this research focused on how age-related changes in COP control strategies affect the performance of tasks with a large range of truncal motion and momenta. It was hypothesized that while performing leaning and downward reaching movements, older women, compared to younger women, would exhibit slower but more frequent COP submovements in order to accomplish the task and regain the upright posture. First, we investigated the limiting factors in downward reach and pick-up movements. Using an age-adjusted proportional odds model, increased SCK difficulty was found to be independently associated with balance confidence, leg joint limitations, and knee extension strength. Secondly, we explored the age-related changes in COP control in healthy women. Despite being 27% slower, older women rely on nearly twice as many submovements to maintain a similar level of endpoint accuracy in volitional COP movements, particularly when moving posteriorly. Furthermore, older women used slower primary submovements that more often undershot their target, in comparison to young women, particularly as movement amplitude increased. Lastly, healthy older women were found to lose their balance more often than young women in downward reaching tasks, but rely on similar COP control strategies when successful. Modeling results suggest that a simple forward dynamic model that accounts for changes in musculoskeletal factors may distinguish between healthy young and healthy older women with and without SCK difficulty. We conclude that biomechanical factors can distinguish between older women with and without SCK difficulty. Given the significance of the rate of torque development in arresting downward reaching movements, changes in COP control may be effective tools in evaluating early signs of physical impairment. Undershooting primary submovements and increased secondary submovements are indicative of an increasingly conservative strategy used by older adults near the limits of the base of support that may explain their slower speeds during whole body movements to maintain balance.Ph.D.Biomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91565/1/manueleh_1.pd