An Investigation Into the Electrical Activity of Tender, Resting Paraspinal Muscles Using Surface Electromyography: A Pilot Study

Abnormal resting paraspinal muscle activity has been claimed to be responsible for changes in spinal tissue texture which are detectible by manual palpation. This pilot study investigated whether there was significant electrical activity in paraspinal musculature that was tender and that appeared to have altered tissue texture on palpation. Sixteen healthy volunteers between 18 and 35 years of age had their thoracic erector spinae mass palpated bilaterally from spinal levels T3 to T10 to identify paraspinal regions exhibiting altered tissue texture relative to the contralateral muscle mass. Surface electromyography (sEMG) was used to measure electrical activity in the muscle mass at the selected levels. No significant differences in electrical activity were observed between the tender and non-tender muscle masses, although a large difference existed in the one symptomatic subject. All muscle sites displayed EMG activity at rest, although the source of activity is not clear. A number of methodological problems with the EMG recording were encountered and are discussed. Future research is recommended using symptomatic participants

CENTRE OF MASS MOTION DURING THE PUNT KICK

Centre of mass (COM) motion has been linked to performance in kicking and cricket bowling. The aim of this study was to examine COM motion during the punt kick. Five elite Australia Footballers performed maximal and sub-maximal punt kicks. Optotrak Certus (200Hz) collected kinematic data and COM and foot speed were calculated. Greater COM deceleration was linked to faster foot speeds. Large effects existed between maximal and sub-maximal kicks for change in COM velocity and average impulse as well as for correlations between these parameters and foot speed within the maximal kick. Approach speed was significantly larger for maximal kicks but the relationship was unclear with a negative correlation with foot speed existing within maximal kicks. More work with larger N examining COM deceleration is recommended

KICK IMPACT FORCES FOR DIFFERENT RUGBY BALL SIZES, IMPACT POINTS AND INFLATIONS

The purpose of this study was to evaluate force characteristics of impact during kicking rugby balls of different size and inflation pressures and with different foot-ball contact positions. A mechanical kicking limb struck rugby balls of sizes 3 (smallest), 4 and 5 (used in senior competition). Foot and ball speed, contact time and distance and impact forces were calculated from 2D high speed video (4000 Hz). Overall, average contact force decreased as the ball size decreased. Decreasing inflation pressure also decreased average contact force. Finally, contacting the ball in the middle section produced lower forces than for similar kicks contacting the point of the ball. Manipulating ball size, inflation and contact position provides a platform for progressive kick-specific conditioning

The Probability of Choosing Primitive Sets

We generalize a theorem of Nymann that the density of points in Z^d that are visible from the origin is 1/zeta(d), where zeta(a) is the Riemann zeta function 1/1^a + 1/2^a + 1/3^a + ... A subset S of Z^d is called primitive if it is a Z-basis for the lattice composed of the integer points in the R-span of S, or, equivalently, if S can be completed to a Z-basis of Z^d. We prove that if m points in Z^d are chosen uniformly and independently at random from a large box, then as the size of the box goes to infinity, the probability that the points form a primitive set approaches 1/[\zeta(d)\zeta(d-1)...zeta(d-m+1)].Comment: 11 page

SHOT SUCCESS AND KINEMATIC DIFFERENCES WITH ALTERING KICKING POSITION ON GOALSHOOTING TECHNIQUE IN AUSTRALIAN FOOTBALL

In Australian Football, goalshots are taken from a range of distances and angles to the goal. The aim of this study was to evaluate if performance and technique differed for goalshots from different sides of the posts. Seventeen players performed 10 goalshots from two different positions (45° to the left (L45) and 45° to the right (R45) of goals) on an Australian Football ground. Kicking kinematics were measured using the Xsens MVN link inertial measurement system (240Hz). Shot success was slightly better for kicks from the left (62 v 59%). Technical differences were limited with small effects evident for knee and shank angular velocity. Individual differences were evident that indicate that individual-based analysis is necessary for future goalshooting work

MAINTAINING A FIRM ANKLE: AN EFFECTIVE COACHING CUE FOR IMPROVING FOOTBALL KICKING?

Kicking with high ball speed is important across football codes. Maintaining a firm ankle during impact has been used as a coaching cue to improve kick performance. However, biomechanical studies of human kickers have identified conflicting results, questioning its effectiveness. Recent mechanical modelling has identified reduced ankle plantarflexion was associated with increased impact efficiency, and the aim of this paper was to determine if reduced ankle plantarflexion was associated with increased impact efficiency in human kickers. An intra-individual analysis of human players was performed. Foot-ball impact characteristics were recorded at 4,000 Hz. Impact efficiency was highest when ankle plantarflexion during impact was minimised

THE ASSOCIATION BETWEEN UNILATERAL BALANCE AND KICKING

Balance is a common coaching cue and technical factor associated with kicking in the football codes. The aim of this study was to compare balance ability and maximal kick performance for the punt kick. Fifteen elite junior Australian Football players performed maximal punt kicks with their preferred and non-preferred legs with foot and ball speed calculated using VICON. Balance ability was assessed unilaterally during three 20 s standing tasks on a force plate using centre of pressure range and medio-lateral force standard deviation. No relationship was found between balance ability and kick performance, similar to soccer kicking. Future work should explore balance in more kick-specific tasks

THE IMPACT PHASE OF DROP PUNT KICKING: VALIDATION AND EXPERIMENTAL DATA OF A MECHANICAL KICKING LIMB

The purpose of this study was to validate a mechanical kicking limb and analyse changes in foot speed on impact characteristics of drop punt kicking. Foot speed was recorded as 9.1 - 21.2 mls, and covered a range of kick distances. Ball speed (13.0 - 29.7 m/s), contact distance (10.7 - 20.2 cm) and contact time (14.75 - 11.75 ms) were comparable to drop punt kicking. lmpact efficiency (F:B ratio = 1.37 - I .48, coefficient of restitution = 0.66 - 0.79) were high, caused by near perfect rigidity in the design of the limb. Overall, the limb was found to be a valid representation of a human performer. Foot speed displayed significant relationships with ball speed (r = 0.998), contact time (r = -0.89), contact distance (r = 0.99) and F:B ratio (r = -0.694). The relationship between foot speed and COR (-0.347) was not significant

THE RELATIONSHIP BETWEEN IMPACT CHARACTERSITICS AND FORCED PLANTAR-FLEXION DURING FOOTBALL KICKING

Reducing the forced plantar-flexion during impact of kicking is beneficial to kick performance. The aim of the present study was to identify the relationship between three impact characteristics with plantar-flexion; ankle stiffness, impact location and foot speed. By using a mechanical kicking machine to control impact characteristics, three separate data sets for each impact characteristics were created from high-speed-video camera (4,000 Hz). Relationships were determined from 1st, 2nd or 3rd order bivariate regressions. A linear relationship existed for joint stiffness, meaning a players’ strength can reduce plantar-flexion. A 2nd order relationship was identified for impact location and impacting the ball closer to the ankle decreased plantar-flexion. A 3rd order relationship was identified for foot speed and dorsi-flexing at the start of impact reduced plantar-flexion