Smith, S.L., Comparisons of Selected with the Flat and Slice Serves of Male Varsity Tennis Players in Proceedings of the Na- THE RACE DOWN FROM
tional Symposium on Racquet Sports, J.L. Groppel, (ed.), University of Illinois, Champaign, 17,1979. "Impact Absorption in Extended Downhill
Trabert, T., The Slice Serve, Tennis Strokes and Strategies, Simon and Schuster, New York, 1975. Van Gheluwe, B., and M. Hebbelinck, The Kinematics of the Service Movement in Tennis: A Three Dimensional Cinematographic Ap- . R.N. Marshall, Paterson and P. Glendining proach, Biomechanics IX-B, D.A. Winter, R.W. Norman, R.P. Wells, K.C. Hayes and A.E. Palta (eds.), Human Kinetics Pubs., Champaign, The University of Western Australia, Illinois, 521-526, 1985. University of Oxford, Van Gheluwe, B., I. De Ruysscher and J. Craenhals, Pronation and dorotation of the Racquet Arm in a Tennis Serve. Biomechanics X-B B. Jonsson (ed.) Kinetics Pub., Champaign, Illinois, 667-672, a.m. on November 27,1987 forty five runners from eight countries started the world's highest marathon. The Marathon began at Gorak Shep (at an altitude of 5184 metres, just below the Camp), and finished at Namche Bazaar (altitude 3446 m). In addition to being the world's highest marathon, it also involved the most downhill run- ning. Total descent was approximately 2138 m, including the effect of two major uphill portions (see Figure 1). Competitors trekked into Namche Bazaar, and then on to Gorak Shep over a 2.5 week period. This allowed enough time for acclimatisation, and for them to become acquainted with Marathon was held for several reasons. Apart from provid- ing a spectacular athletic event, the organisers raised money for charities
working in Nepal, and promoted awareness of conservation problems in the Sagarmatha (Everest) National Park. It also provided a unique oppor- tunity for biomechanical and physiological research. The race was run on mountain trails, which frequently provided uncer- tain footing due to loose rocks and gravel. In addition, runners had to con- tend with the normal traffic on the trails (including yak trains), as it was impossible to clear the route for the race. Contrary to many opinions ex- pressed before the race, no serious injuries were sustained. Forty two run- ners finished the race, and three stopped after completing 32.2 km. Al- though several competitors had previously recorded times, the race was won in and only nine runners finished in under RELATED LITERATURE
(1988) has recently reviewed the general literature on eccentric muscle actions and their relationship to delayed on set muscle pain. He notes that the pain is particularly associated with unfamiliar and high force le work, and that the pain is usually noticed after about eight hours, s maximal 24 to 48 hours later. With specific reference to running, and Cavanagh (1987) reported high levels of muscle soreness 24 to 48 hours after 40 minute downhill run on a -10% grade. Running on the level involves eccentric action of the knee extensors for ashort period after impact. This occurs while the quadriceps are activated, but the knee joint is flexing. Buczek and Cavanagh (1987) found maximum knee flexion to average 0.77 radians (44 degrees) and occur at 34% of the stance phase. They contrasted this to running on a -10% slope, where a greater and later maximum knee flexion was seen (0.84 radians, 41% of stance). In both of these situations, the knee joint typically flexes on im- pact, and then extends for the remainder of stance. Buczek and Cavanagh also reported knee angles at impact for level and negative slope running, and found a decrease in average knee angle at impact from 0.44 radians to 0.30 radians for downhill running. A qualitative analysis of running, such as that outlined by Hay and Reid Marathon Altitude by (1982, pp. 310) allows evaluation of running style. A model of this sort should also permit an assessment of the effects of external variables on the significant mechanical factors involved. Thus, one might predict the Preparations for the race by the organisers were necessarily thorough gesmost likely to occur as a result of altering the slope of theterrain. Chan- and intensive. One of the major concerns was that runners might develop ges found in running downhill are likely to be in body position at foot strike high altitude pulmonary (mountain sickness). Eight doctors ac- and toe-off, and in the different height of take off and landing. All three companied the runners during the trek in, and in conjunction with two of these factors affect stride length, and only one (relative height at fors in the region set up ten well-equipped medical posts along the race off) affects stride frequency. One would expect, therefore, to see more route. Runners were advised of the benefits of acetazolamide (Diamox), a noticeable changes in frequency during drug which has been shown to enhance acclimatisation to altitude, and it downhill running. was available under supervision from the doctors in the group. Virtually Another factor expected in running on a negative slope would be in- all the runners used the drug, and only a few cases of mild mountain sick- creased energy absorption demands being placed on the body at impact ness were recorded. with the ground. This could be catered for by those joints normally as- One of the main interests in the race from a biomechanical point of view sociated with negative work at heel strike, namely the ankle and knee joints. was the opportunity to study the runners' to the effects of There are at least two possible approaches to altering the energy absorp- such a long period of downhill running. Specifically, we were interested in tion potential of a joint: change the joint angle at impact to permit a greater their responses to the problem of energy absorption at impact, and the ef- range of movement over which to perform negative work; or increase the fects of prolonged eccentric work by the knee extensors. stiffness of the eccentrically acting muscles. Thus we might expect to see either changes to the ankle and kneejoint angles at heel strike, or enhanced electromyographic activity of the eccentric muscles prior to heel strike. could be used by runners to reduce energy absorp- tion requirements would be to decrease step length and increase step articipating in an activity involving prolonged repetitive quency. This would reduce the vertical kinetic energy of the runner at le actions, this group reported no cases of severe muscle pact, yet maintain their speed. Approximately25 experienced marathon runners were filmed at the 25 and 41 kilometre points in the marathon (the villages of Tengboche and Bazaar respectively). Camera speeds, track slopes and linear scaling s were forced to include a considerable amount of eccentric factors were calculated, and leg length, step lengths, step frequencies, knee angles at impact, and angles of maximum knee flexion were determined for each runner who appeared in both films (N Data from runners who wore baggy leg coverings or who did not run on the track were techniques to minimise the magnitude of the impact shock, and to reduce from the step length and angular data analysis. Normalisation of the magnitude of the forces required at the knee joint. First of all, the step lengths and average velocities was performed in order to remove the solute values for average step lengths were slightly shorter (0.94 m and 0.96 effects of subject anthropometry. Step lengths were normalised to the m respectively vs 1.1 m) than those reported for level running at 3.0 m runner's ankle to hip length to facilitate inter-subject comparisons. Nor- 1978). Expressed as a proportion of leg length, they malised average speed was calculated from the product of normalised step were shorter than the values reported Roy (1982) for distance runners length and step frequency. Data were averaged for each subject, and the (1.07 and 1.09 vs and for downhill running (Nelson and Osterhoudt, change in each variable between the two filming points calculated. 1971; Dick and Cavanagh, although in both of those studies the runners' speeds were greater. Their step frequencies appear to be normal The slope of the track at Tengboche was -0.21 rad (-21.8%). Table 1 shows TABLE 1: Group means and standard deviations (in parentheses) for
the group means and standard deviations for the temporal, and speed and temporal, speed and angular data angular data collected. Normalised step length did not change between Tengboche and Namche Bazaar, but significant differences were seen in step frequency and normalised speed. Thus runners averaged a greater number of steps per second and were running faster at the second testing Normalised step length site. The absolute values of the runners' averaged step lengths were calcu- lated to facilitate comparison with published data, and they were 0.94 m and 0.96 m respectively for Tengboche and Namche Bazaar. No difference was seen in either knee angle at impact or maximum knee Maximum knee angle (rad) 0.90 (0.12) angle during stance between the two filming sites. However, seventeen of the twenty subjects recorded their maximum knee angle at toe-off (100% * significant at p 0.01 Although the runners were not specifically canvassed after the race From this, it appears the runners attempted to limit their kinetic about muscle soreness, not one case of pain was reported, at impact on these steeper slopes by increasing step frequency and and the general comment was that they felt no more sore than after any a relatively constant and moderately short step length. These ges would have the effect of preventing the vertical component of the impact energy from increasing significantly by reducing the vertical drop Dr. R.N. Marshall is on leave of absence from the University of Otago, and would like to acknowledge the support provided by that average, the runners' stance leg impacted the ground with a more in this project during 1987 and 1988. extended knee, and achieved a greater maximum knee flexion in stance ther information on this and future races may be obtained from Ms. when compared to either level or -10% slope running. It would appear the runners attempted to provide a greater range of movement at the knee joint over which the eccentric work would be done. This could permit lower forces to be generated while producing the same net impulse. The majority of the runners did not have a stance knee extension phase when running past the sites. This implies the quadriceps muscle ac- tivity was primarily eccentric and suggests one of the factors in producing micro-trauma in the muscle may be the change from eccentric to con- centric muscle activity in a movement. Another unique aspect of this race was the runners' use of acetazolamide to aid acclimatisation. A side effect of this drug may be to reduce the effects of eccentric muscle activity, although if the major cause of muscle pain is physical damage to muscle fibres and membranes, this is unlikely to be a factor. However, the drug may have an effect on mononuclear cell infiltration or subsequent intramuscular pressure, both of which have been suggested to play a role in the pain. This work has provided a description of some of the biomechanical vari- ables which change with prolonged downhill running. Runners appear to manipulate their step length and frequency to maintain or minimise their kinetic energy at heelstrike. They also vary their knee angle at impact and the total amount of flexion at the knee to provide a greater range of mo- tion over which to do the eccentric work required. Both of the above fac- tors would lend to reduce the magnitude of the muscle forces produced by the knee extensors. The majority of runners also eliminated any knee ex- tension during stance while running on these steep slopes. These and other factors may have interacted to limit the incidence and severity of post-race muscle pain. The authors would like to thank the runners for their cooperation, and the following organisations for their financial and other assistance: Bufo Ven- tures Ltd., England, Highland Sherpa Trekking and Mountaineering Pty., Ltd., Kathmandu, Nepal, and Shashi's Travel, Kathmandu, Nepal. REFERENCES
R.L. and Cavanagh, P.R. Knee joint action in level and downhill running (Abstract). Medicine and Science in Sports and Exer-
Dick, R.W. and Cavanagh, P.R A comparison of ground reaction forces (GRF) during level and downhill running at similar speeds (Abstract).
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The height achieved in a vertical jump for maximum height is dependent Motion Prentice-Hall, Englewood Cliffs, New Jersey. 1982.
on the external work done to increase the kinetic energy of vertical trans- lation of the centre of gravity (CG). In turn this work is dependent Luhtanen, P. and Komi, P.V. Mechanical factors vertical component of the ground reaction forces and the displacement speed. In Biomechanics
E. Asumussen and K. Jorgenson, eds. through which the CG is accelerated by these forces during the period of Baltimore, University Park Press, 1978, pp. 23-29. ground contact. Stretching of the elastic components, primarily the Achilles' tendon (Alexander and Bennet-Clark, 1977; van Ingen Schenau, Nelson, R.C. and Qsterhoudt, R.G. Effects of altered slope and speed on 1984; Bobbert, Huijing, and van Ingen Schenau, the biomechanics of running. Medicine and Sport, in increased ('potentiated') vertical force magnitudes (Cavagna, Sabiene, 11, pp. 220-224. Karger, and Margaria, 1965; and Bonde-Petersen, 1974; Komi and D.J. The consequences of eccentric contractions and their Bosco, 1978; Bosco and Komi, 1979; Bosco, Komi, and Ito, 1981). This relationship to delayed onset muscle pain. European Journal
prestretching of the elastic elements may be accomplished by a downward Physiology 57: 353-359,1988.
counter movement prior to the upward movement of the jump. Several re- searchers have studied the effect of elastic energy by comparing jumps per- Roy, B. Caracteriques biomecaniques de la course formed with a counter movements with jumps from a static start- Journal of Applied Sports Sciences
104-115, 1982. Cited in Wil- ing position
and have suggested that the utilisation of stored elastic liams, K. (1985). energy becomes less important at larger amplitudes of knee flexion (Bosco and Komi, 1981; Bosco, Komi, and Ito, 1981; Bosco et al, 1982). This was thought to be due to the longer time period of the jump and the associated dissipation of elastic energy. Modeling of muscle has shown that optimal timing of forces is related to the longer time period of the jump and the associated dissipation of elastic energy. Modeling of muscle has shown that optimal timing of forces is related to the interaction of the elastic and con- tractile elements of the elastic and contractile elements of the system (Denoth, 1983; Bobbert, Huijing, and van Ingen Schenau,
Equine Drugs & Medications Presented by Kathy Ott, DVM – Cleary Lake Veterinary Hospital December 13, 2010 A) Commonly Used Drugs 1) Anti-inflammatories (NSAIDs) 2) Antibiotics 3) Sedatives 4) Steroids Therapeutic Hormonal 5) Muscle Relaxants 6) Antihistamines 7) Blocking Agents 8) Reproductive Drugs 9) Anti-ulcer Drugs 10) Eye medications 11) Dewormers 12) Topicals 13) Diuretics 14) Miscellaneous
Koloskopie und Polypektomie Vorbereitung - Durchführung - Risiken Sehr geehrte Patientin, sehr geehrter Patient, bei Ihnen ist eine Spiegelung des Dickdarmes (Koloskopie) vorgesehen. Die Koloskopie ist eine der wichtigsten Methoden, um Erkrankungen des Medikamenten in der Vorbereitungszeit: unteren Verdauungstraktes frühzeitig zu erkennen