High frequency performance analysis of professional soccer goalkeepers: a pilot study

AIM

High-speed video analysis was performed during ten official-matches, to assess the performance of ten goalkeepers (GK) from Italian third/fourth divisions (C-D).

METHODS

The variables studied were: number (N.) of frontal and lateral actions with distance covered (speed during first-last meter) and total distance covered during match.

RESULTS

Match analysis showed that N. of lateral (right/left) changes of direction in GK-C was 48% (P<0.005) lower, and forward changes of action 53% greater (P<0.001) compared to GK-D. N. of forward and lateral actions in GK-C was 49% and 67% (P<0.001 and P<0.0001) greater than GK-D, respectively. Particularly, in GK-C the covered average distance, frontal and lateral, was 27% and 58% (P<0.005 and P<0.001) greater than in GK-D, respectively. Velocity of first meter of forward and lateral actions for GK-C were 9% and 27% lower (P>0.05 and P>0.05) than GK-D, respectively. Last meter of forward and lateral actions for GK-C was 57% greater and 43% lower (P<0.001 and P<0.005) than GK-D, respectively. Finally, total covered distance, considering all actions, was 60% greater for GK-C compared to GK-D (P<0.001).

CONCLUSION

The work presented in this paper identifies the relevant aspects of the goalkeeper game that are valuable for a coach in terms of team and individual performance analysis.

Validity of the MarkWiiR for kinematic analysis during walking and running gaits

The aim of this study was to validate the MarkWiiR (MW) captured by the Nintendo Wii-Remote (100-Hz) to assess active marker displacement by comparison with 2D video analysis. Ten participants were tested on a treadmill at different walking (1<6 km · h⁻¹) and running (10<13 km · h⁻¹) speeds. During the test, the active marker for MW and a passive marker for video analysis were recorded simultaneously with the two devices. The displacement of the marker on the two axes (x-y) was computed using two different programs, Kinovea 0.8.15 and CoreMeter, for the camera and MW, respectively. Pearson correlation was acceptable (x-axis r≥0.734 and y-axis r≥0.684), and Bland–Altman plots of the walking speeds showed an average error of 0.24±0.52% and 1.5±0.91% for the x- and y-axis, respectively. The difference of running speeds showed average errors of 0.67±0.33% and 1.26±0.33% for the x- and y-axes, respectively. These results demonstrate that the two measures are similar from both the x- and the y-axis perspective. In conclusion, these findings suggest that the MarkWiiR is a valid and reliable tool to assess the kinematics of an active marker during walking and running gaits.

Sprint vs. intermittent training in young female basketball players

AIM

This study aimed at comparing the effects of intermittent and repeated sprint ability training on physiological variables.

METHODS

Sixteen young female basketball players were randomly allocated to intermittent training (IT=8) or repeated sprint ability training (RST=8) groups. The following outcomes were measured at baseline and after 6 weeks of training: Yo-Yo intermittent recovery (Yo-Yo) and repeated sprint ability (RSA) tests.

RESULTS

For all the variables investigated the effect of training type showed a different trend respect at current knowledge. In the RSA, best time (BT) was a significant main effect of training time (pre- vs. post-) (P<0.0001), and of the interaction training type/time (P=0.03). The RST showed a decrease in BT of 3.1% (P=0.005) while the IT showed a decrease of 6.2% (P<0.0001). In the IT there was a significant main effect of time for the total distance with an increment of 26.9%, and a significant main effect of time in the final speed with an increment of 1.23%.

CONCLUSION

These findings suggest that the two training methods used in this study can be an effective training strategy for inducing anaerobic and basketball-specific training schedules. Besides, even when IT training is not done at very high speed, it can increase the maximum speed of the RSA.

Kinematic analysis of soccer players in shuttle running

The intermittent shuttle running test is mainly used within soccer to assess aerobic power. For this reason we studied kinematic parameters and heart rate at both an increasing speed, [Yo-Yo Endurance Lv 1 (Y₁)] and at constant velocity [95% maximal aerobic velocity (MAV(95%))]. 12 soccer players were selected for this study. A high-speed digital camera (210 Hz) was used to record motion; Dartfish5.5Pro was used to perform 2D video analysis and heart rate was also recorded and computed during the test. The parameters considered (baseline measures with respect to the end of each test) in this study were: step length (SL), contact time (CT) and heart rate (HR). SL: 40% in Y1 and -22% in MAV(95%). CT: -31% in Y1 and 29% in MAV(95%). HR: increased 96% in Y1 and 17% in MAV(95%). These results highlight 2 different neuromechanical strategies adopted under fatigued conditions. In light of the clear changes of the CT in MAV(95%) (29%) and with respect to the moderate changes in HR (17%) it is clear that the CT is the most important parameter, as it experiences greater adaptations associated with neuromuscular patterns, under a fatigued condition as opposed to HR.

[Efficacy and safety of ambulatory electric cardioversion of atrial fibrillation with monophasic and biphasic shock]

BACKGROUND

The aim of this study was to evaluate the safety and efficacy of ambulatory external cardioversion (EC) by means of monophasic and biphasic shock in patients with persistent atrial fibrillation (AF).

METHODS

One hundred and twenty-seven consecutive patients with AF were submitted to EC, preceded by short general anesthesia with propofol, after pretreatment with oral anticoagulants for at least 3 weeks and, if not contraindicated, with amiodarone. In 87 of these patients we used monophasic shock and in 40 patients we used biphasic shock. Our protocol provided for up to 3 shocks delivered at an energy level ranging between 200 and 360 J for monophasic and from 70 to 175 J for biphasic shock. The patients were discharged after 4 hours of ECG monitoring and following a determination of serum CK-MB at the fourth hour.

RESULTS

The mean age of the patients submitted to EC with monophasic and biphasic shock (65 +/- 9 vs 67 +/- 7 years) and the duration of AF (34 +/- 22 vs 32 +/- 25 days) were similar. The efficacy of EC with monophasic shock was 85% and the mean energy delivered was 266 +/- 81.5 J. The efficacy of the EC with biphasic shock was 98% and the mean energy delivered was 127 +/- 40 J. The difference between the percentage of efficacy and the number of joules delivered was statistically significant (p < 0.05). The mean value of the CK-MB after 4 hours following delivery of the shock was not significantly different: 2.5 ng/ml for monophasic vs 1.7 ng/ml for biphasic shock (p = NS).

CONCLUSIONS

In our patients, ambulatory EC of persistent AF is safe and feasible; biphasic shock is more efficacious and requires less energy with respect to monophasic shock.

Chemiluminescent choline biosensor using histidine-modified peroxidase immobilised on metal-chelate substituted beads and choline oxidase immobilised on anion-exchanger beads co-entrapped in a photocrosslinkable polymer

A novel sensing layer design is presented based on the non-covalent immobilisation of enzymes on derivatized Sepharose beads subsequently entrapped in PVA-SbQ photopolymer. Two different modified Sepharose beads were used, IDA- and DEAE-Sepharose, for the immobilisation, respectively, of horseradish peroxidase (HRP) modified with histidine, and choline oxidase (Chx). The HRP-IDA-Sepharose-based sensing layer was used in a flow injection analysis chemiluminescent system as the basis of an H2O2 biosensor. It was shown that the pre-immobilisation on IDA-Sepharose beads enhanced the sensing layer stability and enabled the immobilisation of a larger amount of enzyme. A 1.8 mg charge of HRP-IDA-Sepharose beads in the sensing layer produced the most sensitive H2O2 biosensor. Such an analytical system exhibited very good performances, with a cycle time of 2 min and a detection limit of 15 pmol (detection ranging over four decades at least), and an unusual long operational stability of 200 measurements (CV, 3.5%). The HRP-IDA-Sepharose beads were then combined with Chx-DEAE-Sepharose. With this modified Sepharose-based biosensor the limit of detection for choline (S/N, 3) was equal to 0.5 pmol and the working range was 0.35 pmol-10 nmol. Moreover, the cycle time was only 2.5 min with the new sensing layer, and a long operational stability of 150 successive assays was found, with a variation coefficient of 2.6%.