Biomedical subjects
Publications and source records attributed to R Stretch.
Two first class cricket bowlers presented with costoiliac pain secondary to rib impingement. In both patients, conservative management of the injury had failed to improve symptoms. Surgical resection of the affected rib was undertaken. At follow up, both patients had made a good recovery and had returned to competitive cricket.
BACKGROUND: The varying methods of cricket injury surveillance projects have made direct comparison of published studies in this field impossible. METHODS: A consensus regarding definitions and methods to calculate injury rates in cricket was sought between researchers in this field. This was arrived at through a variety of face-to-face meetings, email communication and draft reviews between researchers from six of the major cricket-playing nations. RESULTS: It is recommended that a cricket injury is defined as any injury or other medical condition that either: (a) prevents a player from being fully available for selection for a major match or (b) during a major match, causes a player to be unable to bat, bowl or keep wicket when required by either the rules or the team's captain. Recommended definitions for injury incidence (for matches, training sessions and seasons) and injury prevalence are also provided. It is proposed that match injury incidence is calculated using a denominator based on a standard time estimated for player exposure in matches, for the purposes of simplicity. This will allow all injury surveillance systems, including those with limited resources, to make calculations according to a standard definition. CONCLUSION: The consensus statement presented provides a standard which, if followed, allows meaningful comparison of injury surveillance data from different countries and time periods, which will assist in the possible identification of risk factors for injury in cricket.
BACKGROUND: The varying methods of cricket injury surveillance have made direct comparison of published studies in this field impossible. METHODS: A consensus regarding definitions and methods to calculate injury rates in cricket was sought between researchers in this field. This was arrived at through a variety of face to face meetings, email communication, and draft reviews between researchers from six of the major cricket playing nations. RESULTS: It is recommended that a cricket injury is defined as any injury or other medical condition that either (a) prevents a player from being fully available for selection for a major match or (b) during a major match, causes a player to be unable to bat, bowl, or keep wicket when required by either the rules or the team's captain. Recommended definitions for injury incidence (for matches, training sessions, and seasons) and injury prevalence are also provided. It is proposed that match injury incidence is calculated using a denominator based on a standard time estimated for player exposure in matches, for the purposes of simplicity. This will allow all injury surveillance systems, including those with limited resources, to make calculations according to a standard definition. CONCLUSION: The consensus statement presented provides a standard which, if followed, allows meaningful comparison of injury surveillance data from different countries and time periods, which will assist in the possible identification of risk factors for injury in cricket.
A cinematographic analysis of the drive off the front foot (D) and the forward defensive stroke (FD) was undertaken to establish the kinematic and kinetic factors involved in playing these strokes against medium-fast bowling. Fourteen provincial cricket batsmen were filmed at 100 Hz while batting on a turf pitch with a specially instrumented bat. Results for the drive off the front foot revealed that the movement and stroke pattern were generally supportive of the coaching literature, with the forward defensive stroke forming the basis of the drive. Certain mechanical differences, although non-significant, were evident to facilitate the attacking nature of the front foot drive and included a higher backlift (FD = 0.65 m; D = 0.74 m), later commencement of the stride (FD = 0.64 s pre-impact; D = 0.58 s pre-impact) and downswing of the bat (FD = 0.38 s pre-impact; D = 0.36 s pre-impact), a shorter front foot stride (FD = 0.72 m; D = 0.68 m) with the front foot placement taking place later (FD = 0.14 s pre-impact; D = 0.06 s pre-impact), and the back foot dragging further forward at impact (FD = 0.05 m; D = 0.10 m). The front upper limb moved as a multi-segmental series of levers, which resulted in the drive showing significantly greater (P< 0.05) peak bat horizontal velocity at 0.02 s pre-impact (FD = 3.53 +/- 3.44 m s(-1); D = 11.8 +/- 4.61 m x s(-1)) and 0.02 s post-impact (FD = 2.73 +/- 2.88 m x s(-1); D = 11.3 +/- 4.21 m x s(-1)). The drive showed a significantly greater (P < 0.05) bat-ball closing horizontal velocity (FD = 24.2 +/- 4.65 m x s(-1); D = 32.3 +/- 5.06 m x s(-1)) and post-impact ball horizontal velocity (FD = 6.85 +/- 5.12 m x s(-1); D = 19.5 +/- 2.13 m x s(-1)) than for the forward defensive stroke. The point of bat-ball contact showed nonsignificant differences, but occurred further behind the front ankle (FD = 0.09 +/- 0.17 m; D = 0.20 +/- 0.13 m), with the bat more vertical at impact (FD = 62.6 +/- 6.53 degrees ; D = 77.8 +/- 7.05 degrees). Significant differences (P< 0.01) occurred between the grip forces of the top and bottom hands for the two strokes, with the principal kinetic finding that the top hand plays the dominant role during the execution of the drive with the bottom hand reinforcing it at impact. Similar grip force patterns for the two strokes occurred during the initial part of the stroke, with the drive recording significantly greater (P < 0.05) forces at 0.02 s pre-impact (top hand: FD = 129 +/- 41.6 N; D = 199 +/- 40.9 N; bottom hand: FD = 52.2 +/- 16.9 N; D = 91.8 +/- 41.1 N), at impact (top hand: FD = 124 +/- 29.3 N; D = 158 +/- 56.2 N; bottom hand: FD = 67.1 +/- 21.5 N; D = 86.2 +/- 58.2 N) and 0.02 s post-impact (top hand: FD = 111 +/- 22.2 N; D = 126 +/- 28.5 N; bottom hand: FD = 65.5 +/- 26.9 N; D = 82.4 +/- 28.6 N).
Monkeys were trained to emit 10 responses to terminate a schedule complex consisting of a light and masking noise in the presence of which brief, intravenous injections of naloxone (0.01 mg/kg per injection), dl-cyclazocine (0.003, 0.01 mg/kg per injection), or saline were scheduled to occur over blocks of consecutive daily sessions. Completion of the fixed ratio (FR 10) response requirement terminated the schedule complex, producing a time-out of 60 s in which responses were without consequence and injections did not occur. Sessions lasted for 100 min or ended after 100 injections, whichever came first. When monkeys received an intramuscular injection of morphine (10 mg/kg) 60 min preceding each session, responding to avoid injections of naloxone or cyclazocine was well maintained, though morphine-dependent monkeys tolerated injections of saline or the vehicle in which cyclazocine was dissolved. When the morphine pretreatment regimen was discontinued, monkeys tolerated injections of naloxone and cyclazocine though, at the larger cyclazocine dose (0.01 mg/kg per injection), responding was maintained for at least 30 consecutive sessions in two postdependent animals, but not in two other monkeys treated identically. The capacity of these morphine-antagonist drugs to support responding that avoids their injection depends evidently upon whether monkeys are rendered morphine dependent or not; in the case of cyclazocine, however, an increased sensitivity to the negative-reinforcing effects of the drug appears to persist in some "postdependent" monkeys.
This study provides evidence that mother--infant separation in macaques is a useful experimental model of depression. At the age of 6--8 months, seven M.fascicularis infants underwent two consecutive separations from their mothers lasting 21 and 15 days, respectively. The frequency and duration of a set of individual and social behaviours were recorded throughout each of the following experimental conditions: baseline, separation, reunion. In response to maternal separation, the infants showed marked increased in frequency of behaviours reflecting distress, self-directed activity or anxiety (e.g. vocalization, locomotion, body play). Both individual and social play behaviours were markedly suppressed in separated infants. During the second separation, one group of subjects was given, in a 'double blind' fashion, daily doses of 5 mg/kg of an antidepressant, desmethylimipramine (DMI), i.m. Treatment with DMI markedly diminished most of the behavioural alterations induced by separation. In particular, the increases in distress and self-directed behaviours as well as the suppression of play activities were prevented or antagonized. Plasma levels of DMI after 5 days of administration were in the range of 50--150 ng/ml.
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The separate effects of graded doses of morphine, naloxone, d,l-cyclazocine, and d-amphetamine on responding maintained by a differential reinforcement of low rate schedule of food presentation were examined in rats. Morphine did not alter response rates at doses of 1--5.6 mg/kg; at 10 mg/kg a 57% decrease in responding was observed and behaviour was even more severely depressed by 30 mg of morphine per kilogram. Naloxone did not affect responding at doses ranging from 0.1 to 10 mg/kg. d,l-Cyclazocine at doses of 3 and 5.6 mg/kg induced substantial increases in responding not observed when the dose was increased to 10 mg/kg. Cyclazocine, as well as morphine, produced dose-dependent decreases in the number of reinforcements per session. d-Amphetamine exerted a biphasic effect on responding; small doses increased response rates (0.3--3 mg/kg) and responding was suppressed by the drug at a dose of 10 mg/kg. Behaviourally active doses of d-amphetamine caused a dose-dependent reduction in the number of reinforcements per session. Naloxone at otherwise inactive doses (1--10 mg/kg) was found, in separate experiments, to antagonize the rate-decreasing effects of morphine, and to reduce the rate-increasing effects of d-amphetamine. The latter effect is not easily interpreted but confirms and extends other research employing rats in which naloxone was found to reduce the rate-increasing effects of small doses of d-amphetamine upon locomotor activity and responding maintained by a continuous electric-shock postponement procedure. In additional experiments morphine was given daily for 25 consecutive sessions at a dose of 30 mg/kg, 5 min preceding each test session. Responding was suppressed throughout this period and the dose of morphine given before each session was reduced to 10 mg/kg for 35 further sessions. Tolerance to the rate-decreasing effects of morphine was demonstrated; naloxone given in conjunction with morphine (10 mg/kg) in morphine-tolerant rats restored to control values the number of reinforcements per session without causing significant change in overall rates of responding. Few experiments have dealt previously with the development of tolerance to the behavioural effects of morphine under comparable dose regimens, time-course relationships, or behavioural testing procedures. Systematic analyses of these interrelated variables are needed since it is now evident that the schedule employed to maintain responding itself exerts significant effects.
Responding for intravenous injections of morphine was studied using a discrete-trials procedure in squirrel monkeys. For one group, each session consisted of 10 trials at an inter-trial interval of 15 min; for the second group, each session consisted of 100 trials at an inter-trial interval of 1.5 min. When different injection doses of morphine (1-1000 mug/kg per injection), including saline as a control procedure, were substituted at random for blocks of five consecutive sessions, the frequency of morphine self-administration was found to be an inverted U-shaped function of the injection dose. This relationship was observed in each group of monkeys, despite a 10-fold difference in the total amount of the drug which was available for self-administration per session when a given injection dose was substituted for both groups. The results show that the injection dose of morphine acted as a primary determinant of response probability, even under circumstances in which trial spacing imposed a significant delay between consecutive opportunities for drug self-administration,
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Rates of lever pressing, maintained either by response-dependent intravenous injections of cocaine (250 mug/kg per injection) or by food-pellet presentation, were compared and found to vary systematically as a function of the delay (5-100 s) imposed between the response(s) and the occurrence of reinforcement. The control of responding by two schedules of delayed reinforcement was studied. The first scedule permitted responses to occur during the delay period without any programmed consequence; the second schedule required a response, and then the elapse of x seconds without any additional response(s). At imposed delays of 50 and 100 s, response rates were reduced significantly when the second schedule was in effect by comparison with the first. The effect was observed when responding was maintained either by intravenous cocaine injections or by food-pellet presentation. Across all comparable conditions, response rates were higher when maintained by scheduled cocaine injections than by food pellets. Rate enhancement, generally induced by drugs of the psychomotor stimulant type, could account for the observed difference.
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After stabilization of response rates engendered by a free-operant avoidance contingency, the lever-pressing of two squirrel monkeys was maintained for several months by a fixed-interval schedule of electric shock presentation. Initially, response-contingent shocks produced substantial increases in response rates. Continued exposure to the schedule resulted in a reduced overall rate accompanied by a change in the temporal patterning of responses. There was a pause in responding after most shock deliveries; the rate of responding then increased during the interval to reach a terminal value preceding shock presentation. Omission of shocks for part of the daily session led to higher rates of responding; the reintroduction of response-contingent shocks produced a lower overall rate and reinstated the temporal patterning of responding characteristic of the fixed-interval schedule.