Alycia Fong Yan

Impact attenuation during weight bearing activities in barefoot vs. shod conditions: A systematic review

Although it could be perceived that there is extensive research on the impact attenuation characteristics of shoes, the approach and findings of researchers in this area are varied. This review aimed to clarify the effect of shoes on impact attenuation to the foot and lower leg and was limited to those studies that compared the shoe condition(s) with barefoot. A systematic search of the literature yielded 26 studies that investigated vertical ground reaction force, axial tibial acceleration, loading rate and local plantar pressures. Meta-analyses of the effect of shoes on each variable during walking and running were performed using the inverse variance technique. Variables were collected at their peak or at the impact transient, but when grouped together as previous comparisons have done, shoes reduced local plantar pressure and tibial acceleration, but did not affect vertical force or loading rate for walking. During running, shoes reduced tibial acceleration but did not affect loading rate or vertical force. Further meta-analyses were performed, isolating shoe type and when the measurements were collected. Athletic shoes reduced peak vertical force during walking, but increased vertical force at the impact transient and no change occurred for the other variables. During running, athletic shoes reduced loading rate but did not affect vertical force. The range of variables examined and variety of measurements used appears to be a reason for the discrepancies across the literature. The impact attenuating effect of shoes has potentially both adverse and beneficial effects depending on the variable and activity under investigation.

Shock attenuation in shoes compared to barefoot: a systematic review

Background The debate over the advantages and disadvantages of barefoot versus shod running has gained momentum recently [1,2] with the retail market aiming to mimic the motion of the foot during barefoot gait[3]. The aim of this study was to conduct a systematic review of articles that compared shock attenuation in the shod condition to barefoot during weight bearing activity in healthy individuals.

Comparison of lower limb stiffness between male and female dancers and athletes during drop jump landings

Repetition of jumps in dance and sport training poses a potential injury risk; however, non‐contact landing injuries are more common in athletes than dancers. This study aimed to compare the lower limb stiffness characteristics of dancers and athletes during drop landings to investigate possible mechanisms of impact‐related injuries. Kinematics and kinetics were recorded as 39 elite modern and ballet dancers (19 men and 20 women) and 40 college‐level team sport athletes (20 men and 20 women) performed single‐legged drop landings from a 30‐cm platform. Vertical leg stiffness and joint stiffness of the hip, knee, and ankle were calculated using a spring‐mass model. Stiffness data, joint kinematics, and moments were compared with a group‐by‐sex 2‐way analysis of variance. Multiple linear regression was used to assess the relative contribution of hip and knee and ankle joint stiffness to variance in overall vertical leg stiffness for dancers and athletes. Dancers had lower leg (P < 0.001), knee joint (P = 0.034), and ankle joint stiffness (P = 0.043) than athletes. This was facilitated by lower knee joint moments (P = 0.012) and greater knee (P = 0.029) and ankle joint (P = 0.048) range of motion in dancers. Males had higher leg (P < 0.001) and ankle joint stiffness (P < 0.001) than females. This occurred through lower ankle range of motion (P < 0.001) and greater ankle moment (P = 0.022) compared to females. Male and female dancers demonstrated reduced lower limb stiffness compared to athletes, indicating a more pliable landing technique. Dance training techniques could potentially inform approaches to injury prevention in athletes.

Correlates of Perceived Ankle Instability in Healthy Individuals Aged 8 to 101 Years

OBJECTIVES To provide reference data for the Cumberland Ankle Instability Tool (CAIT) and to investigate the prevalence and correlates of perceived ankle instability in a large healthy population. DESIGN Cross-sectional observational study. SETTING University laboratory. PARTICIPANTS Self-reported healthy individuals (N=900; age range, 8-101y, stratified by age and sex) from the 1000 Norms Project. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Participants completed the CAIT (age range, 18-101y) or CAIT-Youth (age range, 8-17y). Sociodemographic factors, anthropometric measures, hypermobility, foot alignment, toes strength, lower limb alignment, and ankle strength and range of motion were analyzed. RESULTS Of the 900 individuals aged 8 to 101 years, 203 (23%) had bilateral and 73 (8%) had unilateral perceived ankle instability. The odds of bilateral ankle instability were 2.6 (95% confidence interval [CI], 1.7-3.8; P<.001) times higher for female individuals, decreased by 2% (95% CI, 1%-3%; P=.001) for each year of increasing age, increased by 3% (95% CI, 0%-6%; P=.041) for each degree of ankle dorsiflexion tightness, and increased by 4% (95% CI, 2%-6%, P<.001) for each centimeter of increased waist circumference. CONCLUSIONS Perceived ankle instability was common, with almost a quarter of the sample reporting bilateral instability. Female sex, younger age, increased abdominal adiposity, and decreased ankle dorsiflexion range of motion were independently associated with perceived ankle instability.

The effect of jazz shoe design on impact attenuation

The findings of lower calf girth, BD (indicating tibial width) and age in TSF cases support previous literature, and suggest an inability to withstand applied load. A direct link between lower BMI and increased risk of TSF was not well established, but may have similar implications. The results for the other variables suggest that gaitrelated factors have less effect on TSF risk in this population. This may be due to the high fitness requirements for entry to RM training and, by implication, non-injurious running gait. Initial results suggest that individuals at high risk of TSF may be identifiable through simple measures of BMI, calf girth and BD taken at the start of training.

Biomechanics of footwear design

Background The aim of the workshop is to explore the effects of footwear design on lower limb motion and discuss research findings relevant to the clinic and physical activity. Delegates will be actively involved in a motion capture process where important lower limb joint stress variables will be displayed in real time. The University of Sydney researchers will raise footwear issues from a range of areas such as children physical activity, adult walking and running, specific footwear such as thongs (flip-flops), dance and experimental methodology. During or on completion of this workshop, participants will be able to: • Critically analyse footwear characteristics that are likely to influence lower limb function during physical activity. • Experience the use of state of the art technology to analyse lower limb mechanics. • Discuss the models and methods used to build knowledge about the effect of footwear on lower limb mechanics. • Recount clinical and research outcomes for the effect of footwear on lower limb biomechanics during physical activity. • Apply biomechanical principles to the effective choice of footwear for a range of physical activities.

MAXIMUM HEIGHT OF A DANCE JUMP IN DIFFERENT JAZZ SHOES

Golf is one of the world’s most popular sports, enjoyed and played by many millions of people, neither physical ability, skill level or age a barrier to participation, both the amateur and professional equally likely to succumb to the tantalizing challenges posed by the sport. Perhaps the thrill of striking that golf ball in the sweet spot of the club head and seeing it vanish into expanses of a golf course, with the green fairways surrounded by trees providing a most relaxing setting, is too pleasurable an experience to be enjoyed alone. However, there is a very demanding aspect of the sport. The act of hitting a golf ball is one that requires an inordinate amount of attention and skill from the player; a ball the size of a plum to be struck with a small club head appended to an angled implement rotating at high angular speed, places demands on the motor coordination system that seem well beyond human capacity. Golf is perhaps one of the most technically demanding and high precision sports that humans can participate in, often driving its participants to despair. Yet, there is a strong alluring aspect of the sport to counter this. The experience of hitting a golf ball to the point of mastery is most enjoyable, even to the extent that some turn to the poetical or mystical to gain further insight into the experience, the golfer in the movie ‘The Legend of Bagger Vance’ serving as a classic example. Whatever said and done, one thing is clear: golf certainly captivates the human imagination. Given then that golf is a source of fascination for so many people, and for so many different reasons, what contribution can biomechanics make to the sport? The answer to this is relatively simple. Whatever the competition level, or the purpose, satisfaction on the golf course is dependent on the golfer having attained a certain degree of proficiency in the golf swing, a task of no mean feat, the casual amateur golfer finding it difficult to break 100 on any given day. Furthermore, even more regular competitors find consistent performance elusive, experiencing large fluctuations in performance, some days scoring in the single figures, the game seeming relatively easy, the ball travelling as intended from club to target with minimal effort, contrasted with days when the game seems inordinately difficult, the club becoming as unwieldy as a shovel, the ball seeming as small as a marble, the whole task of hitting the ball impossibly hopeless. Professionals are also not immune from such slumps in performance, one week playing at levels of supreme excellence, winning a tournament with ease, several strokes ahead of the nearest competitor; to be contrasted with a performance only a short time after, when stroke making is so difficult that even making the cut seems a herculean task. More tragic is the case when professional players have significantly lost their ability to swing a golf club, something that has afflicted a number of players, sometimes after an attempt to make a swing change, other times for no conceivable reason at all, the loss of form lasting for years, or worse, permanently. All this shows that the golf swing is not a simple motion, the appearance of simplicity in the professional golf swing being a rather deceptive one, even a cursory qualitative examination of its mechanical elements revealing a surprising degree of complexity. To hit a golf ball with speed and accuracy, the golfer has to perform a number of mechanical feats, such as swinging the golf club on multiple planes, propelling the club head on time-varying trajectories, rotating the body segments on multiple planes, rotating the body segments in a particular sequential order, combining rotary motion with linear motion, all the while controlling the kinematicJumping is a key skill in dance and the effect of different dance shoes on jump performance is not known. Female pre-professional and professional dancers (n=14) were recruited to perform consecutive maximum vertical jumps in second position in four types of jazz shoes and barefoot, with and without music. An overall effect of the jazz shoes was found both with and without music (p<0.001), and music reduced jump height significantly (p<0.001), although no interaction was found between music and shoe condition. High-heeled shoes reduced maximum jump height, while the other jazz shoe styles were not significantly different to barefoot. The results of this study assist dancers, teachers and clinicians with shoe selection. Future research should examine the mechanisms of takeoff and landing in dance jumps in different shoes.