Journal of Sports Sciences

ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage:

Conference communications To cite this article: (1991) Conference communications, Journal of Sports Sciences, 9:4, 393-451, DOI: 10.1080/02640419108729899 To link to this article:

Published online: 14 Nov 2007.

Submit your article to this journal

Article views: 25

View related articles

Full Terms & Conditions of access and use can be found at Download by: [York University Libraries]

Date: 06 November 2015, At: 23:04

Journal of Sports Sciences, 1991, 9, 393-451


Downloaded by [York University Libraries] at 23:04 06 November 2015

Communications to the Sport and Science Conference Held at St Mary's College, Strawberry Hill, Twickenham, Middlesex, 4-9 September 1991


PART I: BIOMECHANICS Evaluating and reporting errors in biomechanical data and their possible effects

R.M. Bartlett and CJ. Payton Division of Sport Science, Crewe and Alsager College of Higher Education, Alsager, Stoke-on-Trent ST7 2HL, UK The objective of this study was to consider the effects of errors in biomechanical measurements on computed parameter values and ways in which such errors can best be estimated. Few reported biomechanical studies pay due attention to the existence of errors in their measurements, and even fewer consider their possible effects on computed parameter values. Thus, for example, Terauds (1978, Track and Field Quarterly Review, 78,25-8) compared the distances thrown with the theoretical ranges in vacuo (using measured speed, angle and height) for six men's discus throws at the Montreal Olympics. This showed that, at the extremes of the range, Schmidt threw 6.71 m less than the theoretical range (R), while Thiede threw 7.01 m further. Terauds attributed this to 'different effects of the air' and failed to question whether, at this elite level, such differences between throwers were likely. The calculations presented assume fairly small errors in his release parameter values of ± 1 ° in release angle (a), ± 1 m s~1 in release speed (v) and + 1 cm in release height (h). With partial derivatives of dR/da= - 4 0 . 6 m r a d " \ dR/dv = 4.S0 s and dR/dh= 1.34 m, the paper shows that these errors can accumulate to a computed range error of over + 5 m! It should be noted that the magnitudes of these assumed errors in Terauds' release variables are considerably smaller than those given in the literature for release of the javelin, as summarized by Bartlett and Best (1988, Journal of Sports Sciences, 6,1-38). It is likely that the errors in the release values for a two-dimensional study of a three-dimensional event would have considerably exceeded those assumed in the above calculation. This would imply that the in vacuo differences discussed by Terauds were probably due to measurement errors rather than to real inter-thrower differences. In conclusion, it is recommended that parameter values obtained from film/video co-ordinate digitization should not be used for calculation of other quantities unless the effects of measurement errors are carefully evaluated and reported. While repetitive digitizing remains the best way of 0264-0414/91 $03.00+ .12 © 1991 E. & F.N. Spon


Conference communications

estimating the random part of such measurement errors, the assessment of systematic errors and data reliability and objectivity should also be considered.

Pressure distributions on the plantar surface of the foot during the discus throw R.M. Barlett,1 E. Muller,2 C. Raschner2 and F. Brunner 2

Downloaded by [York University Libraries] at 23:04 06 November 2015

^Division of Sport Science, Crewe and Alsager College of Higher Education, Alsager, Stoke-on-Trent ST7 2HL, UK and 2Institutfur Sportwissenschaften der Universitdt Innsbruck, Furstenweg 185, A6020 Innsbruck, Austria The objectives of this study were to measure the pressure distributions on the plantar surface of the foot during the discus throw (a unique investigation to date) and to validate the overall vertical forces measured by an E-MED insole against those recorded simultaneously from a force platform. The study was carried out at the University of Innsbruck, with a right-handed, 23-year-old discus thrower of reasonable standard (50 m plus) and having a good technique. The methodology conformed to that for other single-subject biomechanical studies. After calibration, an E-MED pressure insole was carefully fitted into the sole of the thrower's left shoe (Adidas Universal). Following habituation and warm-up throws, pressures were recorded for three throws at the maximum possible sampling rate of 100 Hz. The throws were video-recorded and, simultaneously, a Kistler Model 928IB force platform was used to record the three components of ground reaction forces, at a sampling rate of 200 Hz, for the landing of the left foot at the front of the circle. Pressures were analysed for the push-off into the entry (single foot pivot) phase and for front foot landing at the front of the circle at the start of the delivery phase. Comparisons of the total vertical force from the E-MED insole and the force platform showed the two to follow very similar trends with identical numbers of peaks and troughs, the mean discrepancy in the times of occurrence of which was only 15 ms, close to the accuracy with which measurements could be taken from the final graphical displays. The mean discrepancy between the forces registered at these turning points (where the discrepancies were at their greatest) was 170 N; the differences are probably due mainly to the different sampling rates and the summing of forces from 85 individual transducers in the insole. The greatest peak pressures were recorded during the push-off from the rear of the circle (Table 1) on metatarsals 2-5, with a similar peak pressure on the first metatarsal (MT1) for throws 1 and 3. At landing, peak impact pressures occurred on the first metatarsal (MT1) with a later, smaller active peak concentrated on the hallux, where the greatest pressure integral was also recorded. The peak pressures measured in this study were slightly smaller than those previously reported for the triple jump (Nichol, 1977, Leistungssport, 7, 220-27) and running. Because of the insight which these measurements provide into aspects of technique and as both peak pressure and the pressure-time integral have been considered to have implications for soft tissue damage, further such studies of athletic events are recommended using larger numbers of subjects.

Table 1. Summary of plantar pressures

Throw no. 1 2 3

Drive into entry, peak pressure, kPa (site)

Landing for delivery, peak pressure, kPa (site)

Max. pressure, integral, Pa (site)

5OO(MT2-5) 620(MT2-5) 580 (MT1, MT2-5)

460 (MT1) 500 (MT1, MT2-5) 490 (MT1)

135 (hallux) 136 (hallux) 139 (hallux)

Conference communications


A three-dimensional video analysis of the kinematic differences between experienced and novice skiers performing two types of parallel ski turn H. Brierley and R.M. Bartlett

Downloaded by [York University Libraries] at 23:04 06 November 2015

Division of Sport Science, Crewe and Alsager College of Higher Education, Alsager, Stoke-on-Trent ST7 2HL, UK The objectives of the study were (a) to investigate the feasibility of using three-dimensional video analysis on sloping terrain and with a large calibration volume, and (b) to identify the differences between the techniques of a novice and an experienced skier performing two types of ski turn - the upunweighting and down-unweighting. A 6.72 x 3.03 x 2.0 m volume was defined by four specially constructed poles each with five known spherical marker positions. Two subjects were filmed performing the two turns on a dry ski slope using two gen-locked Panasonics electronically shuttered video-cameras filming at 50 fields per second. One of each type of turn per subject was chosen for analysis on the basis of the highest perceived success rating by the performer. Conversion from two-dimensional image space to three-dimensional object space co-ordinates was performed using a DLT algorithm which compensated for linear lens distortion. The reconstruction accuracy of known test points had a mean error of about 90 mm, which was judged acceptable for such a large volume and as the test points were at the extremes of the volume. Many differences were found between skill levels. The experienced skier (E) raised his mass centre more than the novice (N) at turn initiation for both types of turn, which would result in a reduction of pressure at the ski-slope interface, thus aiding turning. Displacements from the centre of rotatory movement of the skis showed similar tendencies but different ranges for forward and backward (E = 0.28 m, N = 0.20 m) and into and out of the turn (E = 0.35 m, N = 0.05 m). Hip-shoulder separation showed the novice to make insufficient use of the counter rotatory method of transmitting a moment to the skis. Whereas the experienced skier maintained a positive separation until 0.68 s into the turn, the novice had a negative separation as early as 0.13 s, for the up-unweighting turn. Hip and knee angulation differed, with the inside hip of the experienced skier having a greater maximal extension (E= 128°, N = 120°, up-unweighting). This study showed that results of acceptable accuracy can be obtained with the methodology used for this difficult example. The differences between skill levels were similar to those reported by earlier investigators.

The experimental determination of muscle model parameters in vivo J.H. Challis and D.G. Kerwin Department of Physical Education and Sports Science, Loughborough University of Technology, Loughborough LEU 3TU, UK This study reports a procedure for determining the parameters for a muscle model, and the validation of this model. Three muscles causing elbow flexion were modelled - the biceps brachii, brachialis and brachioradialis. Each muscle model consisted of a contractile component representing the muscle fibres, in series with an elastic component representing the tendon. The force produced by the contractile component was dependent on the length, velocity and degree of activation of the muscle fibres. Non-linear models of the force-length and force-velocity relationships were used. Tendon elasticity was modelled using Hooke's Law. Osteometric scaling, from dry bone specimen to experimental subject, was used to define the locations of the origins and insertions of the three elbow flexors on the experimental subject. Muscle-tendon complex lengths were determined in vivo assuming that each muscle's line of action was

Downloaded by [York University Libraries] at 23:04 06 November 2015


Conference communications

straight from origin to insertion. Parameters for the force-length model for each muscle were determined using a non-linear optimization algorithm. The model parameters were systematically varied until a best fit was obtained to a number of experimentally determined joint torques measured during maximal isometric contractions, at different degrees of elbow flexion. Parameters for the force-velocity relationship were obtained from the literature. Solution of a first-order differential equation, relating the rate of change of muscle force to the rate of change of tendon length, permitted the muscle model to estimate muscle forces during a maximal dumb-bell curl. The sum of the moments caused by the three muscles gave an estimate of the net muscle moment about the elbow joint during this activity. The muscle moments were also computed using inverse dynamics. Comparison of these two sets of muscle moment values indicated the validity of the muscle model and its parameters. The mean difference between the two muscle moment data sets was 0.37 (±2.15) Nm, indicating that in this case the accuracy of the model provided an acceptable representation of the muscles causing elbow flexion.

A biomechanical and physiological analysis of two sport knee braces/supports during running

E.L. Debbage and N.F. Mullan Division of Sport Science, Crewe and Alsager College of Higher Education, Alsager, Stoke-on-Trent ST7 2HL, UK The objective of this study was to examine the effect of knee brace application during running on certain biomechanical and physiological parameters. Eight subjects (four females and four males) completed two experimental tasks. The first task was a 12-min endurance run on a motorized treadmill at a set speed (2.69 m s" 1 for females, 3.58 m s" 1 for males). Pre- and post-exercise fingertip blood samples were taken in order to measure lactate concentrations. The second task involved running across a force platform at a constant pace (5.0 m s " 1 ) . Ground reaction forces and knee joint movement parameters (via video analysis) were recorded. One trial was carried out in each of three conditions: (1) a hinged brace with medial and lateral hinges; (2) an unhinged brace/support; (3) no brace application. The data were analysed using repeated t-tests for correlated means. The results revealed no significant differences (P>0.05) across any of the conditions for post-exercise lactate concentrations, maximum knee flexion angle and vertical, medial-lateral and anterior-posterior (accelerating) ground reaction force variables (Table 1). There was a significant difference between the unhinged and no-brace condition for anteriorposterior active force (decelerating) and between braced conditions for anterior-posterior impulse (decelerating). The unhinged brace was noted to have reduced horizontal braking. Although only two statistically significant differences were found, the raw data revealed the following Table 1. Group mean ( ± S . D . ) values for measured parameters Conditions Parameter Lactate (HIM) Max. knee flexion (") Peak vertical impulse (BW) Peak vertical loading rate (BW s"') Anterior-posterior active force (Ace) (BW) Anterior-posterior active force (Dec) (BW) Vertical impulse (N.s) Medial-lateral impulse (N.s) Anterior-posterior impulse (Ace) (N.s) Anterior-posterior impulse (Dec) (N.s)



No brace

4.39±1.19 130 ±6.60 2.76 ±0.54 263 ±160 0.48 ±0.08 0.50 + 0.11 89.5±27.1 9.04 + 9.54 15.1 + 1.95 18.8 ±8.42

4.15 + 1.11 131 ±7.21 2.17 + 0.68 171 ±47.1 O.5O±O.O9 0.45 + 0.14 80.8 + 19.1

3.96 ±1.22 131 + 5.19 2.34±0.37 197 ±67.4 0.47 ±0.08 0.50 ±0.13 88.6±31.6 8.11±8.67 13.91±1.34 18.2+11.5

6.68 ±6.83 15.4±3.53 15.8±8.16

Conference communications


trends for the majority of subjects. Lactate concentrations appeared to increase, knee angles decrease and there were associated increased impact forces, loading rates, medial-lateral stablility and reduced horizontal braking forces with brace application. This study revealed differences in certain biomechanical and physiological parameters when knee braces were worn in running, although the majority of these were not statistically significant. The potential benefits of wearing a brace for knee stability or prevention from injury may be dependent on brace fit and come at the expense of impaired performance.

Take-off characterisitcs of the women's long jump

Downloaded by [York University Libraries] at 23:04 06 November 2015

N. Fowler and A. Lees Centre for Sport and Exercise Sciences, Liverpool Polytechnic, Byrom Street, Liverpool L3 3AF, UK The aim of this study was to investigate the take-off characteristics of six leading British female long jumpers competing in the national AAA/WAAA championships during 1990. The touchdown and take-off for each jump was filmed in the sagittal plane at 100 Hz. The best two jumps of each performer were analysed in detail. The centre of gravity (CG) of the performer was obtained from a digitization of 18 joint centres and other body landmarks, together with appropriate segmental data. The CG velocity, height and angle of its velocity vector with respect to the horizontal were computed throughout the contact phase, as well as the touchdown velocity, loss of velocity and distance of the CG to ankle at touchdown. These data were computed using a Hanning filter applied twice to obtain smoothed co-ordinate data, and a three-point finite difference method to obtain velocity. The mean height of take-off was found to be 1.27 m, the mean speed of take-off 7.71 m s" 1 and the mean angle of take-off 20.8°. The Pearson product-moment correlation coefficient of each of these with official distance jumped was 0.86, 0.90 and —0.01 respectively. The data presented here can be compared to similar data obtained from elite performers at the 1984 Olympic Games and the 1986 World Championships. It was found that the differences in mean distance jumped between the performers of this study and those of the two international championships was 6 and 10% less respectively, which compared well with the differences in take-off speed of about 10 and 11% less respectively between the subjects of this study and the other two groups. This and the above correlations with official distance of jump confirmed that the take-off speed was a prime performance parameter, and that this is sustained as both a within-group and between-group performance parameter for elite athletes. The mean loss of horizontal velocity was 2 . 8 1 m s " 1 . The mean distance of the CG to the ankle joint at touchdown was 0.49 m, and the correlation with loss of speed was — 0.086. This suggests, contrary to the opinions of coaches, that if the distance the leading leg is placed in front of the CG at touchdown is increased, this will not accentuate the loss in horizontal speed.

Biomechanical assessment of running gait and running-induced injuries

P.N. Grimshaw and M.J. Sinclair School of Physical Education and Sport, West London Institute of Higher Education, Borough Road, Isleworth, Middlesex TW7 5DU, UK The purpose of this study was to investigate the use of biomechanical assessment of the running gait cycle in order to attempt to interpret some of the effects of, reasons for and preventions of injury. Five subjects were examined (three males, two females) who presented with a number of different problems associated with running, e.g. hip problems, shin splints, stress fractures, over-pronation and

Downloaded by [York University Libraries] at 23:04 06 November 2015


Conference communications

over-supination, plantar fasciitis and chondromalacia patellae. The subjects were filmed using video (50 Hz) while running on a treadmill, from the rear view and the side view at various camera positions. Each video sequence was then digitized, using the Biomechanics Workstation (Salford), and a number of parameters were examined during the the gait cycle: knee flexion/extension; hip oscillation; arm movement; ankle plantar/dorsifiexion; pronation and supination (with and without orthotics); time for stance and time for gait cycle. These parameters were then evaluated against normal values (Cavanagh, 1990, Biomechanics of Distance Running. Champaign, 111.: Human Kinetics) and against the subjects' history of injury and treatment. In certain cases, it was possible to identify obvious causes (Table 1) of the injury or irritation (i.e. chondromalacia patellae from prolonged and over-pronation, or hip problems from an apparent uneven leg length). However, in other cases, a number of unusual parameters presented that could have caused an injury or irritation but biomechanically did not appear to do so. It is recommended that the whole kinematic chain should be examined in this type of evaluation considering, in particular, upper-body as well as lower-body movements. However, it is also clear that biomechanical assessment of this nature can and does provide information that is not otherwise readily available. Table 1. Rear foot movement and vertical hip oscillation of subject 1 (running at 4.6 m s 1, during stance phase) who presents with chondromalacia patellae and hip problems (normal values included for comparison) Touchdown angle

Maximum pronation

Total rear foot movement

% Stance phase (max. pronation)

Vertical hip movement (cm)

Subject right left

1.2° 1.6°

7.9° 9.4°

9.1° 11.0°

64 58

19.0 21.1







Without orthotics

The kinematics of the vertical jump for boys aged 5, 6 and 7 years A.J. Harrison Centre for Health Studies, Salford College of Technology, Frederick Road, Salford M6 6PU, UK This study investigated the use of quantitative biomechanical methods to examine changes in vertical jump performance with age. Vertical jumping ability is a prerequisite for a wide variety of specialist sports activities, complex motor skills and games including volleyball, basketball and soccer. An understanding of the process of normal development is important for effective coaching and the physical education of children. Three groups of 10 boys aged 5, 6 and 7 years ( + 2 months) performed three attempts of a vertical jump on a Kistler force platform (Model 9261a). The best jump for each boy was selected for 16-mm film analysis based upon the height of the jump calculated from force trace analysis. Film was obtained using a Bolex 16-mm high-speed camera running at a nominal rate of 64 Hz. The film was analysed using a SAC sonic digitizer to obtain data on joint angles at four key points during the jump. The four key points - start, crouch, take-off and high point - were determined by visual inspection of the film. Mean joint angle positions for all joint angles at the key points were determined for each age group. Comparisons were made between the groups to determine any significant differences in mean joint angle positions using a Student's (-test, and the variance ratio between groups was determined using an F-test. The 16-mm film records of the best and worst performer in each group were selected for a more comprehensive film analysis that included a determination of joint angle-time graphs, angle-angle

Conference communications


plots for hip-knee, shoulder-knee and shoulder-hip. In addition, graphs of joint angular velocity with repect to time were determined for the foot, ankle, knee and hip joints for each group. Statistical significance testing between age groups for joint angle positions at key points during activity indicated the following significant differences: 1. Age 5 compared with age 6: • knee angle at take-off: t value and F value significant (P 130 beats min" \ while only three adults sustained their heart rate at this level for a single 20-min period. There was no significant relationship between spouses for the percentage of time spent with heart

Table 1. The percentage of time adults spend with heart rates < 110, 110-129 and S130 beats min" 1 determined over 3 weekdays and 1 weekend day of continuous heart rate monitoring Weekend

Weekdays Heart rate (beats min " ' ) 75th percentile Mother


12 11

7 6

8 5

8 10 13

5 7 7

5 4 6







8 1

5 1

3 1

"% time spent with: heart rate> 129 beats min beats min" 1 (children).

(adults); heart rate > 139

Conference communications


Downloaded by [York University Libraries] at 23:04 06 November 2015

activity, a greater number of the mother-offspring pairs had values coinciding above the 75th percentile than would be expected by chance alone (> 4 pairs). Similarly, the body mass, systolic blood pressure, triceps skinfold thickness and biceps skinfold thickness measurements of fathers and offspring coincided above the 75th percentile more frequently than would be expected by chance alone (Table 1). The subjects were placed into one of four groups, based on their family history of coronary heart disease. There was no significant difference in the risk factor values of children or parents with no family history of disease compared to the parents and children who had a history of disease on both sides of the family (Table 2 and Table 3). The results from this study suggest that some coronary heart disease risk factors are associated within family groups. Associations between mothers and offspring appear stronger than those between fathers and offspring. Table 2. Coronary heart disease risk factors of family groups with a positive family history of disease Triceps (mm) Subscapular (mm) Sum of skinfold thicknesses (mm) Body mass (kg) Total cholesterol



12.87 + 6.64 13.29±6.16

12.45 + 4.46 8.19 + 2.11

26.16 + 11.78 72.3 ±11.77

20.64 ±5.9 47.1 + 10.4


4.75 + 0.82

118 + 10

100 + 12


67 + 8


Systolic blood pressure (mmHg) Diastolic blood pressure (i.v.) (mmHg)

Table 3. Coronary heart disease risk factors of family groups without a positive family history of disease Children Parents Triceps (mm) Subscapular (mm) Sum of skinfold thicknesses (mm) Body mass (kg) Total cholesterol

14.18 + 5.46 13.27 + 3.31

15.05±5.06 10.1 ±4.02

27.45 + 6.89 71.9 + 9.98

25.15 + 8.81 51.5 + 14.24

5.88 ±1.08

5.06 ±0.77

116 + 14

105 + 12




Systolic blood pressure (mmHg) Diastolic blood pressure (i.v.) (mmHg)

Health-related behaviour modification in family groups Jayne Mitchell, Neil Armstrong and Brian Kirby Physical Education Association Research Centre, School of Education, University of Exeter, Heavitree Road, Exeter, Devon EXl 2LU, UK The importance of, and the potential for, influencing adults through interventions aimed at their children is recognized. The phenomenon has not, however, been widely studied. The present study

Downloaded by [York University Libraries] at 23:04 06 November 2015


Conference communications

examined the health concerns and perceived confidence to make health-related behaviour changes in adults (aged 30-59 years) and their children (aged 11-15 years). The subjects were asked to identify areas of health improvement for themselves and other family members. Children's perceived confidence in their ability to help parents make health-related behaviour changes, and parents' confidence in their own ability to make these changes, were also determined. Questionnaires were completed by 59 adults (25 men, and 34 women) and 42 children (19 boys, 23 girls). There was a significant (P

Communications to the sport and science conference. The Annual Conference of the British Association of Sports Sciences, Middlesex, 4-9 September 1991. Abstracts.

Journal of Sports Sciences ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage: Conference communicati...
4MB Sizes 0 Downloads 0 Views