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Biomedical subjects

B C Elliott

Publications and source records attributed to B C Elliott.

31 records · Page 2Linked to original sources
PubMed1989

A biomechanical analysis of the sticking region in the bench press.

The performance of ten elite powerlifters were analyzed in a simulated competition environment using three-dimensional cinematography and surface electromyography while bench pressing approximately 80% of maximum, a maximal load, and an unsuccessful supramaximal attempt. The resultant moment arm (from the sagittal and transverse planes) of the weight about the shoulder axis decreased throughout the upward movement of the bar. The resultant moment arm of the weight about the elbow axis decreased throughout the initial portion of the ascent of the bar, recording a minimum value during the sticking region, and subsequently increased throughout the remainder of the ascent of the bar. The electromyograms produced by the prime mover muscles (sternal portion of pectoralis major, anterior deltoid, long head of triceps brachii) achieved maximal activation at the commencement of the ascent phase of the lift and maintained this level essentially unchanged throughout the upward movement of the bar. The sticking region, therefore, did not appear to be caused by an increase in the moment arm of the weight about the shoulder or elbow joints or by a minimization of muscular activity during this region. A possible mechanism which envisages the sticking region as a force-reduced transition phase between a strain energy-assisted acceleration phase and a mechanically advantageous maximum strength region is postulated.

Acceleration↗
PubMed1988

The penalty throw in water polo: a cinematographic analysis.

Three-dimensional (3-D) high-speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3-D space reconstruction from 2-D images recorded via laterally placed phase-locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M-162 degrees; F-158 degrees); the elbow angle showed significantly greater flexion for females (85 degrees) than males (107 degrees). During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158 degrees to 148 degrees at release. The wrist movement for male subjects was different from the females in that it flexed from 162 degrees to 147 degrees, 0.10 s prior to release and then extended to 159 degrees at palmar release before again flexing to 156 degrees at release. The amount of elbow extension during the forward swing was 48 degrees for both groups; however, the females actually released the ball with the forearm vertical (89 degrees) compared to the male forearm angle of 78 degrees. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F-148 degrees; M-156 degrees at wrist and F-126 degrees; M-148 degrees at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s-1 and 14.7 m s-1 for male and female subjects respectively.

Adult↗
PubMed1988

Biomechanics of the serve in tennis. A biomedical perspective.

Epidemiological studies have indicated that the serve, arguably the most important facet of the game of tennis, is also the most likely stroke to cause injury, particularly to the elbow and back. A review of the kinematic and kinetic studies on the service action fails to clearly identify the reason(s) for these injuries. Data from these studies does, however, allow possible causes of injury to be postulated. Electromyographic data from the prime mover muscles involved in the serve have shown that muscle action was greater for beginners, whose muscles were active for longer periods than those of advanced players. Ground reaction forces associated with different serving techniques were small compared to those recorded from activities involving running or jumping. The potential to cause injury seems to be related to high internal forces (combination of muscle and joint reaction forces), particularly where these forces are associated with poor technique and high segment accelerations. These situations occur when the racket moves behind the body and the vertebral column is laterally flexed and hyperextended. The pronation of the forearm and the forces associated with the swing to the ball, the impact and the early follow through are also factors that have the potential to cause injury. The action of serving induces strains and pressures upon the body. A sensible approach to the number of serves, particularly when practising (overuse), appropriate physical preparation and a technique that does not introduce excessive forces to selected body parts (misuse) will greatly reduce the potential for injury from this activity.

Athletic Injuries↗
PubMed1984

Biological characteristics of young swimmers, tennis players and non-competitors.

One hundred and twelve finalists in the State Swimming Championships aged between seven and twelve years and 65 ranked tennis players of similar age were selected on the basis of their sporting performances. A third group comprised children of similar socio-economic status who only took part in casual sport. The tests which were used in the study were those considered to be important for successful athletic performance. A multifactorial analysis of variance and post-hoc t-tests were applied to the data to determine if any statistical differences were apparent between the three groups. The results demonstrated that no size, body shape, flexibility, strength or lung function differences were evident between the competitors and non-competitors, but that the swimmers and tennis players were superior to the non-competitors in cardiovascular endurance.

Adipose Tissue↗
PubMed1982

Tennis: the influence of grip tightness on reaction impulse and rebound velocity.

The effect of grip firmness between a tennis racket and a mobile hitting arm on post-impact ball velocity and reaction impulse have been investigated. A pneumatically driven racket-arm was triggered by a stimulus from a photoelectric cell positioned at the exit nozzle of a ball machine so that impact occurred with the racket perpendicular to the path of the ball. Tennis balls were fired to strike each horizontally positioned racket at four locations: the geometric center of the strings, 5 cm from the center towards the distal end, 5 cm closer to the shaft from the center, and 5 cm above the center. The average horizontal velocity of the ball, both before and after impact, was determined by using stroboscope photography. Reaction impulse (the integral of the force recorded following impact over a period of 50 ms), collected using Kistler force transducers, was photographed from a storage oscilloscope and measured over the 50 ms with a digitizer. A non-significant increase in rebound coefficient and reaction impulse in the direction of the hit were recorded for central impacts with an increase in grip tension. The largest rebound coefficients, and therefore the rebounds with the highest velocity, occurred at the center of the strings with a tight grip. Decreases in rebound coefficients and increases in reaction impulses were recorded for off-center impacts when compared to the central impacts. Significant increases in rebound coefficients were recorded for an increase in grip pressure for off-center impacts.

Biophysical Phenomena↗
PubMed1980

A biomechanical evaluation of the role of fatigue in middle-distance running.

Eight college level runners were filmed using high speed photography at the 500 m, 1,300 m, 2,100 m and 2,900 m stages of a 3,000 m time trial. Kinematic and spatio-temporal data were obtained through an interfaced digitiser computer system. Mean horizontal velocities of 5.18 m/s, 5.17 m/s, 5.18 m/s and 5.16 m/s indicated that minimal variations occurred from the four stages of the trial. No significant changes in biomechanical data were apparent between the first three stages of the trial; however, changes were evident when Stage 4, the 2,900 m mark, was compared to the earlier sections of the trial. With the development of fatigue stride length decreased while stride rate increased to maintain the constant velocity. There was also a small shift to increase the period of support and correspondingly decrease the period of non-support. The leg was more angled at foot strike, the thigh was less extended at the end of the support phase, and the trunk was carried further forward during the running cycle. Success in middle-distance running requires the athlete to maintain an efficient co-ordinated movement pattern over the entire race. The coach who can identify the changes in movement patterns over a race increases the likelihood of success for his athletes.

Biomechanical Phenomena↗
PubMed1979

The synchronization of muscle activity and body segment movements during a running cycle.

Locomotor patterns of running were studied using computerization to synchronize electromyography (EMG) and cinematography (CMG). Surface electrodes monitored the muscle action potentials from rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, semimembranosus, triceps surae and tibialis anterior muscles as 10 female subjects ran on a treadmill at speeds of 2.5 m/s and 3.5 m/s. Averaged integrated electromyograms were formulated to represent action potential levels for various sub-sections of the running cycle. Beginning at foot contact, the running cycle was dominated initially by muscle activity concerned with stabilization. The co-contraction of vastus medialis, vastus lateralis, semimembranosus, tibialis anterior, biceps femoris and triceps surae were associated with clockwise rotation (running from left to right) of the thigh, leg and foot in providing a stable base during the early support phase. Lower limb stabilization then gave way to the powerful driving thrust of the mid and late support phases. This period was characterized by increases in the activity levels from triceps surae and biceps femoris. The co-ordination of inertial effects and secondary muscular activity was associated with leg flexion as the thigh changed direction and with leg extension during the swing phase of running. This conclusion was supported by both EMG and resultant muscle moment of force date. Increased activity from semimembranosus and semitendinosus occurred with cessation of thigh flexion and leg extension prior to the subsequent heel strike. Tibialis anterior also eccentrically contracted to place the foot on the treadmill under control. The increase in the running speed was related to an increase in muscle action potential (in parts of the cycle) where the particular muscle was functional. This increase was paralleled kinetically by an increase in the resultant muscle moment of force level.

Adult↗
PubMed1976

A cinematographic analysis of overground and treadmill running by males and females.

Cinematography was used to biomechanically compare individually selected overground jogging and running velocities with equated treadmill jogging and running by adult males and females. All subjects were regular joggers but not competitive track or cross-country runners. No significant differences were recorded in stride length, stride rate, support time or non-support time for males or females when jogging at velocities of between 3.33 and 4.78 m/s (x = 3.70) or 3.45 and 4.80 m/s (x=3.97) respectively. However, it was demonstrated that at velocities of 4.82 - 6.2 m/s for males (x - 5.41) and 4.85 - 5.76 m/s for females (x = 5.29) significant differences did occur between overground and treadmill running. For both males and females stride length decreased, stride rate increased, and the period of non-support was also significantly less when running on a treadmill as compared to running overground.

Adult↗