Effects of beta-blockers on archery performance, body sway and aiming behaviour.

OBJECTIVES: This study aimed to determine the effect of selective (bisoprolol-5 mg) and non-selective (propranolol-40 mg) beta-blockers on archery performance, body sway and aiming behaviour. METHODS: Fifteen male archers participated in a randomised, double-blind, placebo-controlled, cross-over study and competed four times (control, placebo, selective (bisoprolol) and non-selective (propranolol) beta-blocker trials). Mechanical data related to the changes in the centre of pressure during body sway and aim point fluctuation and when shooting was collected. During the shots, heart rate was recorded continuously. RESULTS: Results indicated that, in beta-blocker trials, although shooting heart rates were lowered by 12.8% and 8.6%, respectively, for bisoprolol and propranolol, no positive effect of beta-blockers was observed on shooting scores. Also, the use of beta-blockers did not affect shooting behaviour and body sway. CONCLUSION: The use of either selective or non-selective single dose beta-blockers had no positive effect on shooting performance in archery during simulated match conditions.

Can heart rate values obtained from laboratory and field lactate tests be used interchangeably to prescribe exercise intensity for soccer players?

This study was undertaken to investigate the relationship between blood lactate concentration ([La]) and heart rate (HR) values obtained during treadmill and field tests at fixed velocities with respect to interchangeability of results to be used in exercise prescription. A total of 22 male soccer players participated in the study. Each player performed exercise tests on a motorized treadmill and in the field with 3-min runs and 30 s allowed for blood sampling. During both tests, velocities at the first, second, and third stages were 8, 10, and 12 km x hr(-1), respectively. Velocity was then increased by 1 km x hr(-1) every 3 min until exhaustion. During the field test, players ran on artificial turf on a 120-m hexagonal track marked with cones placed 20 m apart. Running velocity was controlled by means of audio signals. Blood samples were analyzed immediately with an automated lactate analyzer. HR was monitored continuously at 5-s intervals. Data were analyzed with Student's paired t tests to look for differences between treadmill and field data. Coefficients of variation and Blan-Altman plots assessed agreement of HR and blood [La] values between the 2 tests. Although running velocities corresponding to a fixed blood [La] of 4 mmol L-1 showed significant differences between treadmill and field tests (15.9+/-0.9 vs 14.1+/-0.7 km x h(-1), respectively) (P<.01), no significant difference between HR values was noted (190+/-7 vs 187+/-7, field vs laboratory, respectively). Overall, the mean intermeasurement coefficient of variation was 4.8% (+/-0.9%) for HR. Although the lowest coefficient of variation (2.4%) was found, fairly wide differences between individual field and laboratory HR values at velocities corresponding to fixed blood [La] of 4 mmol.L(-1) cast doubt on the interchangeability of tests.

Running velocities and heart rates at fixed blood lactate concentrations in young soccer players.

The purpose of this study was to examine the running velocities and heart rates at fixed lactate concentrations of young soccer players according to playing position and age. A total of 223 young male soccer players participated in this study. Each player performed incremental exercise tests on a treadmill. Running velocities and heart rates at 2 mmol/L-1, 2.5 mmol/L-1, 3 mmol/L-1, and 4 mmol/L-1 blood lactate concentrations were calculated with use of the spline function. Data were analyzed through analysis of variance to examine differences among various playing positions (ie, defenders, midfielders, and forwards) and 3 age groups (U17, under 17 y; U19, under 19 y; and U21, under 21 y). No significant differences were discerned between defenders, midfielders, and forwards in terms of running velocities and heart rates in accordance with specified lactate concentrations. Running velocities corresponding to all lactate concentrations showed no significant differences at all age groups, but heart rates in soccer players in the U21 and U19 age groups were significantly lower than in the U17 age group. Following a 3-y trial of 20 players, running velocities increased and heart rates decreased at all corresponding lactate concentrations. Results of this study suggest that (1) the endurance performance level of young soccer players is similar for all positions, and (2) heart rates are lowered with age and with training.

Effects of anterior tibial displacement on the proprioceptive functions of soccer players` knee joints.

OBJECTIVE: To investigate the effects of joint laxity on proprioceptive functions of the knee joints of soccer players. METHODS: In this study, we measured anterior tibial displacements and thresholds to detect the knee joint passive motion of 20 healthy soccer players (18.1+/-1.6 years of age). We performed all the measurements in Autumn 2000 in Ankara, Turkey. We applied the Mann-Whitney U test to analyze the relationship between the anterior tibial displacement and threshold to detect the passive motion (TDPM). RESULTS: There were no statistically significant differences between the TDPM values of the knee joints with insignificant laxity differences at different angles, and direction of motion (p>0.05). At 45 degrees of knee flexion and externally directed motion, we found the TDPM of looser knees to be significantly greater (p<0.05). CONCLUSION: Increased knee laxities without any clinical pathologic findings, have negative effects on knee joint proprioception. This is possibly due to the overuse degeneration of the anterior cruciate ligaments, which are the main stabilizers of knee joints.

Running velocities and heart rates at fixed blood lactate concentrations in elite soccer players.

This study was undertaken to examine the endurance performance of elite soccer players, according to age and playing position. A total of 197 male soccer players participated in this study. Each player performed exercise tests on the treadmill that included 3-minute runs and 30-second blood sampling intervals. During these tests, running speeds at the first and second stages were 10 km/hr -1 and 12 km/hr -1, respectively. When these tests were completed, running speed was increased by 1 km/hr every 3 minutes until the runner reached exhaustion. Blood samples were analyzed immediately by means of an automated lactate analyzer. Heart rate was monitored continuously at 5-second intervals. Running velocities and heart rates at 2-mmol/L -1, 2.5-mmol/L -1, 3-mmol/L -1, and 4-mmol/L -1 blood lactate concentrations were calculated with use of the spline function. Analysis of variance was used to analyze data to determine the differences between playing positions (goalkeepers, defenders, midfielders, and forwards) and age groups (older than 30 years of age, between 25 and 29 years old, between 20 and 24 years old, and 19 years old and younger). Statistical significance was set at P<.01. No significant differences were revealed between defenders, midfielders, and forwards regarding running velocities and heart rates and their correlation with specified lactate concentrations. Goalkeepers demonstrated lower endurance performance than players in the other playing positions (P<.001). Running velocities corresponding to all lactate concentrations showed no significant differences in all age groups, but heart rates in soccer players older than 30 years of age were significantly lower than those of players in other age groups (P<.01). Results of this study suggest that the endurance performance level of professional players is similar for players in all positions, except for goalkeepers, and that endurance performance is not adversely affected when a person's age increases beyond 30 years of age.

Energy expenditure of the paraplegic gait: comparison between different walking aids and normal subjects.

The aim of this study was to investigate the energy expenditure of walking with different aids in patients with spinal cord injury (SCI) and to compare the results with normal able-bodied control subjects. The tests were performed on a 20 m indoor path in a comprehensive rehabilitation clinic of a university hospital. Nine male patients with incomplete SCI at various levels from C6 to L2 and nine age- and gender-matched normal able-bodied subjects were enrolled in the study. Two different walking aids were evaluated: walker and crutch. The main outcome parameters--walking velocity, oxygen uptake and oxygen cost--were measured during ambulation with the two different walking aids. There was a statistically significant difference between controls and SCI patients in terms of walking velocity (P<0.001), and oxygen cost (crutches P<0.01; walker P<0.001). SCI patients walked more slowly and less efficiently. When we compared SCI patients' walking with the two different aids, a statistically significant difference was observed in velocity and oxygen cost (P<0.05) in favour of crutches. We concluded that energy expenditure studies are useful tools for giving objective measures to patients at the time of discharge and to encourage them to use efficient assistive devices in their daily activities.