WRIST POSITION AFFECTS HAND-GRIP STRENGTH IN TENNIS PLAYERS

In tennis the wrist is required to be in different degrees of orientation at ball impact depending on the stroke and type of shot being hit. To date, little is known about the interplay between wrist position and grip strength, despite the fact that hitting the ball and firmly holding the racket when the wrist is flexed has been suggested as factor predisposing tennis players to lateral epicondylitis. The aim of this study was to investigate the effect of different wrist positions on isometric grip strength at self-selected grip size. Thirty-seven tennis players performed three isometric contractions at each of the following wrist positions: neutral, extension, flexion, ulnar deviation and radial deviation. Maximal isometric grip force was measured at each wrist position with the use of a hand-held grip dynamometer and then the highest value at each position selected for analysis. Our results are as follows: at neutral the force exerted was 80.2 ± 22.07 (mean ± sd) kg, at wrist extension 56.99 ± 18.40 kg, at wrist flexion 33.96 ± 9.47 kg, at radial deviation 56.26 ± 19.39 kg and at ulnar deviation 56.64 ± 17.60 kg. Our findings show that, compare to the position defined as neutral, the maximum isometric force exerted by the fingers’ flexor muscles is significantly affected (lowered) by wrist position (

The effects of β1-adrenergic blockade on cardiovascular oxygen flow in normoxic and hypoxic humans at exercise

Patients:6 healthy subjects mean age 25.5 years were studied.TypeofStudy:This study determined the effects of selective beta-adrenergic blockade with Lopresor on the oxygen flow in arterial blood (Q̇aO2) and oxygen flow in mixed venous blood (oxygen return, Q̇v̄O2) in humans exercising in normoxia and in acute normobaric hypoxia.DosageDuration:Initially 7.5 mg iv bolus; additional doses up to 30-40 mg until a quasi-complete receptor blockade was achieved.Results:Without Lopresor, PaO2 and PaCO2 were lower in hypoxia than in normoxia. In both hypoxia and normoxia conditions, Lopresor did not induce significant differences in PaO2 and PaCO2 with respect to control condition. Arterialized blood pH was higher in hypoxia than in normoxia and was unaffected by Lopresor. [La]b was higher in hypoxia than in normoxia and was unaffected by Lopresor. The highest [La]b values were observed at 150 W in hypoxia. Without Lopresor the fH, SV, Q̇ and Q̇aO2 increased significantly at exercise in both normoxia and in hypoxia. fH was systematically and significantly higher in hypoxia than in normoxia at each workload. SaO2 and CaO2 were lower in hypoxia than in normoxia. In hypoxia, they also decreased with increasing workload. As a result of this, and despite the lower arterial-venous O2 differences in hypoxia, the O2 extraction coefficient was greater in hypoxia than in normoxia. In normoxia the difference between Q̇aO2 and V̇02 (=Q̇V̄O2) did not change with increasing workload. In hypoxia, Q̇V̄O2 decreased as a function of workload. The resting Q̇v̄O2 value in normoxia was significantly lower than the corresponding invariant values at exercise. In hypoxia the resting Q̇V̄O2 value did not differ significantly from the corresponding value in normoxia. However, the Q̇V̄O2 values at 100 and 150 power (W) in C were significantly lower than the corresponding values in normoxia. With Lopresor, the fH, SV, Q̇, and Q̇aO2 increased significantly during exercised in both normoxia and hypoxia conditions. At rest and at each workload, Lopresor systematically and significantly decreased fH, both in normoxia and in hypoxia. The lower fH at any given V̇O2 implied a significant increase in the oxygen pulse with Lopresor. Q̇ values were found significantly higher at each fH level under Lopresor in hypoxia than in normoxia as a consequence of increased SV. SV values were significantly higher under Lopresor than in control condition in both normoxia and hypoxia. In normoxia, Q̇ was significantly decreased by Lopresor at 100 power (W) exercise and above, and in hypoxia at rest and at 50 W. As in control condition, SaO2 and CaO2 were lower in hypoxia than in normoxia. In hypoxia they also decreased with increasing workload. In both conditions the values observed under Lopresor were not significantly different from those found in control condition. The Q̇v̄O2 decrease as a function of workload in hypoxia paralleled an analogous decrease in SaO2.AdverseEffects:No adverse events were mentionedAuthorsConclusions:The results of the present study are in agreement with the tested hypothesis, as this study showed that selective blockade of beta1-adrenergic receptors decreased Q̇aO2 and Q̇v̄O2 significantly during exercise in normoxia as well as during rest and light exercise in hypoxia.FreeText:Experiments were performed in normoxia and in acute normobaric hypoxia. In both conditions the subjects performed two incremental exercise tests, one without Lopresor and one after having induced quasi-complete beta-adrenergic blockade with Lopresor. Tests: oxygen consumption (V̇O2), carbon dioxide output (V̇CO2), expired ventilation (V̇E), heart rate (fH, electrocardiography), SaO2 (oximetry), hemoglobin (Hb), blood lactate concentration ([La]b), cardiac output (Q̇), stroke volume (SV), arterialized blood carbon dioxide partial pressure (PaCO2), and arterialized blood oxygen partial pressure (PaO2)

Behaviour of haematological parameters in athletes performing marathons and ultramarathons in altitude ('skyrunners')

We observed athletes performing marathons and ultramarathons in altitude over several years to study the behaviour of haematological parameters in order to screen eventual paraphysiological or pathological conditions (sports anaemia). We collected samples from 124 athletes participating in seven races; 23 athletes were recruited in different races: 16 for four times, four for three times, and three for two times. The pre- and post-race values of erythrocytes, haemoglobin and packed cell volume did not show statistically significant differences in the studied athletes. The erythrocytes' indices (MCV, MCH, MCHC) and red cell distribution width (RDW) also were not significantly modified by the strenuous effort. The leukocytes were significantly increased because of immunological involvement during the endurance performance. Platelets and relative indices were not significantly modified. The stability of packed cell volume and haemoglobin in athletes performing training and races in altitude is strong evidence for the use of these parameters as an index of general health status and for illustrating possible abnormal increase because of exogenous stimulation of bone marrow. The preanalytical and analytical accuracy is crucial to assure clinical validity of the collected data: we strictly observed international recommendations in this field

High power coupler for the TESLA superstructure cavities

Published online on JACoWMore and more, accelerators are built with superconducting cavities operating at cryogenic temperatures, and the probability of a ceramic window failure presents increasing problems because of the resulting contamination of the cavities' surfaces and the resulting accelerating electric field degradation. Double ceramic window couplers are required to reduce this risk. The TESLA superstructure cavity requires a new coupler for the higher power input and the coupling characteristics. A cost effective design and fabrication method for these couplers has been developed to meet these demands. This new design presents an alternative to the present TESLA cylindrical ceramic windows, uses two planar disc windows separated by a vacuum space, and is optimized for RF input power, vacuum characteristics, and thermal properties. Two couplers with this design have been fabricated and are presently being tested at DESY, Germany on the RF high power testing stand and will also be tested on a test cryomodule. The design will be discussed in this paper

Maximum anaerobic performance of childhood-onset GH-deficient adults

To date, physical capacity of adults with GH deficiency (GHD) has been studied in terms of muscle strength, contractile properties and aerobic performance. As a result, scanty data are available regarding the maximum anaerobic performance of these patients with reference to healthy controls. Therefore, the objective of this study was to evaluate maximum anaerobic power of adults with GHD and of age-matched controls by two methods, one testing lactacid power (w.;(c)) through a 15-s-maximal bout on a bicycle ergometer, the other testing alactic power (w.;(j)) through a vertical jump on a force platform. Absolute w.;(c)and w.;(j)values were both found to be 35% lower(P<0.04) in GHD patients than in controls. Similarly, peak pedalling velocity (V(peak)) was 21% lower (P<0.04) in patients. When w.;(c)and w.;(j)were respectively normalized for thigh and lower limb muscle plus bone volumes and V(peak)for muscle length, differences between patients and controls were no longer significant. Furthermore, the rate of power loss during the cycling bout was approximately 35% in both groups. This observation was in line with similar delta (peak minus baseline) lactate capillary blood concentrations, being 6.3 mM/l in patients and 7.5 mM/l in controls (NS). Lactacid capacity, which represents the energy extracted from lactate metabolism, normalized for body mass was similar in the two groups. In conclusion, the maximum anaerobic power that can be developed by short-statured childhood-onset GHD adults is significantly lower in terms of absolute values, but not different from that of controls once appropriately normalized. Therefore, the changes in maximum anaerobic power of GH deficient patients seem to be a consequence of their smaller muscle mass