Optojump System Research Articles

Comparison of vertical jump heights in a Czech women's top-league volleyball team

Vertical jumps (vj) are a crucial component of performance in volleyball, with different playing positions demanding varying jump heights. The objective of this study was to analyze the differences in vj height among players from various positions in a czech women’s top-league team. Players (n = 20) underwent testing over three seasons. Vertical jump was assessed using the optojump system across different jump tests: squat jump (sj), countermovement jump (cmj), and cmj with arm swing (cmjfa). Players were categorized by positions: blockers (n = 5), attackers (n = 8), setters (n = 4), and liberos (n = 3). (average jump heights in the order of cmj; cmjfa; sj). Blockers (28.4 ± 4.8; 32.4 ± 4.8; 25.6 ± 3.7 cm), attackers (29.2 ± 5.9; 32 ± 9 cm; 31.5 ± 2.4 cm), setters (25.7 ± 3.2 cm; 27.7 ± 5.8; 26.6 cm) and liberos (27.6 ± 1.6; 32.4 ± 3.3; 26.2 ± 2.8 cm). Blockers and attackers displayed higher vj values compared to setters and liberos, however, the results from the two-way anova across individual tests did not show statistically significant differences in average jump heights among the positions. The findings of this study could assist in optimizing training plans and personalizing conditioning preparation for volleyball players.

Cognitive and Motor Capacities Are Poorly Correlated with Agility in Early Pubertal Children: Gender-Stratified Analysis

This research aimed to identify relations of cognitive and power capacities with reactive agility in pubescent boys (n = 55) and girls (n = 46). Cognitive abilities were evaluated by the Stroop test, while the BlazePod system was used to evaluate agility performance conducting 20 yard shuttle and triangle tests of non-reactive (TCODS) and reactive agility (TRAG), respectively. Performance in jumping power was assessed through the squat jump (SJ), countermovement jump (CMJ), and drop jump (DHJ) utilising the Opto Jump system (Microgate, Bolzano, Italy), while sprinting ability over distances of 10 and 20 m was measured using a photocells system. A principal component was extracted from the four Stroop test variables using factor analysis. Forward stepwise multiple regression analysis was conducted separately for boys and girls to evaluate the multivariate relationships among the predictors and the criterion. Among boys, 80% of the TRAG variance was explained (MultipleR = 0.9), with TCODS and SJ as significant predictors (β = 0.53 and −1.01, respectively). For girls, the TCODS was the significant predictor (β = 0.65), explaining 43% of the variance (MultipleR = 0.65). These results show that (i) cognitive abilities measured with the Stroop test were not a reliable tool for predicting TRAG, (ii) jumping power was a significant predictor of TRAG in boys, and (iii) TCODS was a significant predictor of TRAG in girls. The findings indicated that cognitive abilities do not significantly influence reactive agility in pubescent children. It seems that power features have a greater influence on reactive agility, particularly in boys who have more developed motor skills at this age compared to girls.

ENHANCING STRENGTH CAPACITY FOR TRIATHLON COMPETITORS

Triathlon is a sport that combines three different disciplines: swimming, cycling and running. Athletes have to cover varying distances in each discipline and move quickly from one to the next, making triathlon an extremely demanding sport. This research aims to develop and implement a training program with athletic means in order to optimize the strength capacity of triathletes. This paper sought to identify statistically significant differences between the results recorded by the participants, i.e. the performance of athletes at the beginning and end of the study, following an experimental intervention. The present research was carried out with the participation of 3 male athletes, aged between 20 and 36 years (m = 26), from the triathlon sports branch, with over 4 years of competitive experience, competitor in the National Championship. Strength evaluation was conducted using the Optojump system in the case of the participants who performed one test: Left and Right Leg Jumps (5 jumps). Statistical analysis using the Wilcoxon signed-rank test showed significant differences between the initial and final results for explosive strength, indicating that the improvements were not random but were due to the experimental intervention. The training program had a significantly positive impact on the participants' strength capacity and overall performance.

Reliability and validity of sprint performance using the Alex7 motorizeddevice.

Advancements in technology have recently made it possible to implement effective training solutions across different environmental conditions. This study evaluated the reliability and validity of measures obtained from the innovative motorized device, Alex7 (Inosportas, Lithuania), and differences in speed and kinematic characteristics between resisted and assisted sprinting in young football players. Twenty-seven male athletes (mean age: 16.5 ± 0.8 years; height: 179.5 ± 6.9 cm; body weight: 67.7 ± 8.3 kg) each performed 30-m sprints twice under three different conditions: regular, resisted, and assisted sprinting. The Alex7 device provided the assistance and resistance during sprints. Results were compared with those from Witty timing gates. Ground contact time, flight time, stride length, and pace were measured using the OptoJump system. Reliability was assessed using two-way mixed intraclass correlation coefficients (ICCs) for single measures, the standard error of the mean (SEM), and the coefficient of variation (CV). Pearson's correlation coefficient determined the associations between Alex7 and Witty timing systems. Criterion-referenced validity was based on the mean difference and CV. Systematic bias was determined by limits of agreement using Bland-Altman analysis. Running times obtained using the Alex7 equipment exhibited good to excellent test-retest reliability between sessions (ICC, 0.83-0.94) and good to excellent correlation (Pearson's r = 0.88-0.98) between the Alex7 and Witty systems in both assisted and resisted running conditions. However, the Alex7 device consistently produced longer running times than the Witty device (up to 0.16 s difference, p < 0.001). The different running conditions produced substantial variations in kinematic variables, such as stride length, ground contact time, and running speed (p < 0.001 for all), but the effects on flight time and running pace were smaller. The Alex7 device shows high reliability for creating resisted and assisted running conditions for young football players. However, it tends to overestimate running time, necessitating caution when assessing the time parameters.

THE RELATIONSHIP BETWEEN PES PLANUS SEVERITY AND LOWER EXTREMITY FUNCTIONAL PERFORMANCE IN YOUNG ADULTS

Purpose: To examine the relationship between pes planus severity and lower extremity functional performance in young adults with pes planus. Methods: Volunteers with asymptomatic flexible pes planus aged between 18-25 years were included, and 53 (32 Females) individuals with a mean age of 20.19±1.93 years were evaluated in this study. Navicular drop (ND) test was used to decide the presence and severity of pes planus. Balance and jump tests were used for assessing lower extremity functional performance. Balance performance was evaluated with the Y balance test and jump performance was evaluated with the single leg jump test (SLJ) using the Opto Jump system (Microgate, Bolzano, Italy). Results: On the dominant side, a negative and weak correlation was found between ND values and balance results in anterior and posteromedial directions (p=0.014; r=-0.336, p=0.046; r=-0.276, respectively). On the non-dominant side, a negative and weak correlation was found between ND values and balance results in the anterior direction (p=0.040; r=-0.284). There was no correlation between ND values and SLJ heights in both extremities (p&gt;0.05). Conclusions: In young adults with asymptomatic flexible pes planus, insufficient dynamic balance performance was observed as the severity of pes planus increased, but the severity of pes planus did not affect vertical jump distance. This result suggests that interventions for pes planus severity may also have an effect on balance performance.

Biomechanics and subjective measures of recreational male runners in three shoes running outdoors: a randomised crossover study

We compared biomechanical and subjective data from outdoor running in: habitual (OWN), Saucony Endorphin Racer 2 minimal (FLAT) and Nike Vaporfly 4% (VP4) shoes. We also explored relationships between comfort measures and the collected data. Eighteen male recreational runners ran three 1.5-km trials outdoors, once per shoe. The first 1.1 km was run at a self-selected comfortable (slower) speed, and last 400 m at perceived 5-km race pace (faster). A GPS-enabled smartwatch, 15-m Optojump system, high-speed camera and tibial accelerometer collected biomechanical data. Subjective data on comfort, shoe properties and overall running experience were collected using visual analogue scales (VAS) and rankings. Cadence, leg stiffness and vertical stiffness were greater in FLAT than both OWN and VP4 at the slower speed (trivial to small ES). At both speeds, footstrike angles were smaller in FLAT (small to large ES), while propulsion phase was shorter in VP4 (moderate to large ES). FLAT was ranked as the least comfortable at the slower speed and most likely to cause injury, whereas OWN as the most comfortable and least likely to cause injury. Comfort was not significantly different at the faster speed between shoes. Comfort measures were more strongly correlated to subjective than biomechanical data. The two experimental shoes generally had non-significant or small effects on running biomechanics versus OWN. As VP4 are more like traditional than minimal shoes, these were perceived as more comfortable. Running speed appeared to affect subjective measures. Speed should be considered when prescribing and selecting shoes.

Relationship between Muscle Strength of Knee Stabilizers and Quality of Vertical Jump Performance in Physically Active Female Population

High relationships between muscle strength and various forms of jumps are usually based on the research samples of professional athletes or students of sports and physical education. However such studies are less known in the case of recreational women. This study aimed to determine the relationship between isokinetic parameters of knee joint muscle strength with the efficiency of performing vertical jumps. The sample represents a group of 16 healthy and physically active women (age=31.04±3.71; height 168.13±8.34; weight 59.80±9.80). Knee extensors and flexors were evaluated by using an isokinetic dynamometer, while the two-foot vertical jump performance was measured using the Opto Jump System. Pearson's correlation coefficient was used to determine correlation magnitude (p&lt;.05). The obtained results indicated high correlations of the knee extension peak torque dominant leg (KEPT D), knee extension peak torque non-dominant leg (KEPT ND) and knee flexion peak torque non-dominant leg (KFPT ND) with counter movement jump free arms (CMJFA) (r=.525; r=.511; r=.594; p&lt;.05). High correlations was also indicated between KFPT ND with counter movement jump (CMJ) (r=.514; p&lt;.05). Given that these are recreational women, we can assume that the countermovement free arm jump type was the most natural form of expressing their explosive potential. It is certainly important that future studies further examine the relationships between muscle strength and performance of primary and specific motor tasks in recreational women.

The Response to the Training Load in the Aquatic Environment in Terms of the Stimulation of the Reflective Capabilities of Elite Synchronized Swimmers

Summary The youngest swimming sport included in the Summer Olympic Games since 1984 is synchronized swimming. Since the synchronized swimming is still growing popularity and professionalization, it is important to search for ways to improve sports performance. There are few scientific studies focusing also on the biological and motor indicators of top athletes. The present study examined biological and motor variables of elite synchronized swimmers (SYN, N = 13) in ages of 16.5 ± 3.23 years and compare the frequency of Angiotensin Converting Enzyme (ACE) gene genotypes among elite female synchronized swimmers and the non-athletic control group (CON, N = 30) in ages of 16.0 ± 0.6 years. The motor variables were measured using Optojump system before and after water training session. All measurements were collected by trained data collection staff. The ACE I/D variation differences between groups were identified by Chi-Square test. The results of motor variables obtained were evaluated statistically using the Wilcoxon Signed-Rank Test. The strength of association between selected biological and motor variables was measured by Spearman’s correlation. We provided evidence for significant differences of variation of the ACE I/D polymorphism between observed groups. A significant correlation among biological and motor parameters of SYN was demonstrated among the percentage of fat and the time of reflection (p = 0.042), the basal resting heart rate and the jump height (p = 0.006) and among the basal resting heart rate and the power (p = 0.012). The SYN significantly increased only their contact time in jumping (p &lt; 0.016) after the training session. Based on the results we state that the effect of intervention in the stimulation of the reflective capabilities due to the training session in the aquatic environment was not confirmed in the study.

Validity and Reliability of a Photoelectric Cells System for the Evaluation of Change of Direction and Lateral Jumping Abilities in Collegiate Basketball Athletes.

The validity and reliability of the Optojump system were investigated for jumping height and flight time in vertical jump tests. Conversely, the purpose of the present study was to investigate the validity and reliability of the Optojump system for measuring contact time and lateral displacement in change of direction and lateral jump tests. Thirty basketball collegiate athletes were tested on two 10 m sprints with a 60° (COD60) or 180° (COD180) change of direction, lateral controlled (CLRJ) and maximal (MLRJ) rebound jump, and lateral countermovement (LCMJ) and squat (LSJ) jump with the concomitant use of two force plates and the Optojump system for the measurement of contact time in COD60, COD180, CLRJ, MLRJ, and lateral jumping distance in all the lateral jump tests. Almost perfect coefficients (r ≥ 0.95) emerged for contact time in COD60, COD180, CLRJ, MLRJ, although a systematic bias was found for COD60 (−0.01 s). Good-to-excellent reliability was found for almost all the measurements of contact time and lateral jumping distance for change of direction and lateral jump tests. Therefore, the use of Optojump system for testing change of direction and lateral jumping abilities should be executed with caution, avoiding misinterpretation of data.

Effect of 12 Week Neuromuscular Weighted Rope Jump Training on Lower Extremity Reaction Time

The purposes of this study were to determine the influence of a jumping training protocol, using the weighted rope, on lower extremity visual and auditory reaction time performance in adolescent taekwondo (TKD) athletes. Twenty-two elite taekwondo athletes were randomly divided into two groups: the weigthed rope-trained (WRT) group (n = 11) and the control group (n = 11). Subjects in WRT group had jumping training 3 times a week for 12 weeks in addition to the routine taekwondo training program. The control group had no any training protocol in addition to the routine taekwondo training program. The visual and auditory reaction time performances of the subjects, both dominant and non-dominant legs were assessed with the Optojump System. The results of Paired Simple T test showed that the WRT decreased both the visual and the audiotory reaction time of non-dominant leg from pre to post-training (p=0,00, p=0,01 respectively). Although the pre-training audiotory and visual reaction times of dominant were similar between the groups (p>0,05), the post-training visual reaction time of dominant leg was significantly lower in the WRT group compared to control group (p=0,01). This study demonstrates that the weighted rope training program is effective in decreasing the reaction time in dominant and non-dominant leg. It is suggested that the WRT can be applied as an effective exercise program for enhancing visual and auditory reaction time performance.

Effects of volleyball plyometric intervention program on vertical jumping ability in male volleyball players.

This study aimed to investigate the effect of a 6-week plyometric exercise training program on the development of lower limb explosive power in terms of vertical jumping ability in university level volleyball players. The study involved 9 male volleyball players from the AWF Wroclaw University Sports Club, with a minimum of 5 years of training and competition experience. The program consisted of various bounds, hops, and jumps in vertical, horizontal, and mixed directions. During the program, a progressive overload of plyometric intervention was applied. Lower limb explosive power in the form of vertical jumping ability was developed and tested. The jumping ability was evaluated via 5 types of maximum-effort vertical jumps, using the Opto Jump system. In addition, once each week, the heart rate was recorded using a heart rate monitor (Polar RS300X GPS). The only significant correlation was found between squat jump and number of jumps and between counter movement jump and heart rate. From a practical standpoint, the improvement, which was noticed after 3 and 6 weeks, seems to optimal period for volleyball players adaptation to significant increased training load.

Validity of the Jump-and-Reach Test in Subelite Adolescent Handball Players

Muehlbauer, T, Pabst, J, Granacher, U, and Büsch, D. Validity of the jump-and-reach test in subelite adolescent handball players. J Strength Cond Res 31(5): 1282-1289, 2017-The primary purpose of this study was to examine concurrent validity of the jump-and-reach (JaR) test using the Vertec system and a criterion device (i.e., Optojump system). In separate subanalyses, we investigated the influence of gym floor condition and athletes' sex on the validity of vertical jump height. Four hundred forty subelite adolescent female (n = 222, mean age: 14 ± 1 year, age range: 13-15 years) and male (n = 218, mean age: 15 ± 1 year, age range: 14-16 years) handball players performed the JaR test in gyms with region or point elastic floors. Maximal vertical jump height was simultaneously assessed using the Vertec and the Optojump systems. In general, significantly higher jump heights were obtained for the Vertec compared with the Optojump system (11.2 cm, Δ31%, Cohen's d = 2.58). The subanalyses revealed significantly larger jump heights for the Vertec compared with the Optojump system irrespective of gym floor condition and players' sex. The association between Optojump- and Vertec-derived vertical jump heights amounted to rP = 0.84, with a coefficient of determination (R) of 0.71. The subanalyses indicated significantly larger correlations in males (rP = 0.75, R = 0.56) than in females (rP = 0.63, R = 0.40). Yet, correlations were not significantly different between region (rP = 0.83, R = 0.69) as opposed to point elastic floor (rP = 0.87, R = 0.76). Our findings indicate that the 2 apparatuses cannot be used interchangeably. Consequently, gym floor and sex-specific regression equations were provided to estimate true (Optojump system) vertical jump height from Vertec-derived data.

Concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height in female sub-elite youth soccer players.

BackgroundThe aim of the present study was to verify concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height.MethodsNineteen female sub-elite youth soccer players (mean age: 14.7 ± 0.6 years) performed three trials of countermovement (CMJ) and squat jumps (SJ), respectively. Maximal vertical jump height was simultaneously quantified with the Gyko system, a Kistler force-plate (i.e., gold standard), and another criterion device that is frequently used in the field, the Optojump system.ResultsCompared to the force-plate, the Gyko system determined significant systematic bias for mean CMJ (−0.66 cm, p < 0.01, d = 1.41) and mean SJ (−0.91 cm, p < 0.01, d = 1.69) height. Random bias was ± 3.2 cm for CMJ and ± 4.0 cm for SJ height and intraclass correlation coefficients (ICCs) were “excellent” (ICC = 0.87 for CMJ and 0.81 for SJ). Compared to the Optojump device, the Gyko system detected a significant systematic bias for mean CMJ (0.55 cm, p < 0.05, d = 0.94) but not for mean SJ (0.39 cm) height. Random bias was ± 3.3 cm for CMJ and ± 4.2 cm for SJ height and ICC values were “excellent” (ICC = 0.86 for CMJ and 0.82 for SJ).ConclusionConsequently, apparatus specific regression equations were provided to estimate true vertical jump height for the Kistler force-plate and the Optojump device from Gyko-derived data. Our findings indicate that the Gyko system cannot be used interchangeably with a Kistler force-plate and the Optojump device in trained individuals. It is suggested that practitioners apply the correction equations to estimate vertical jump height for the force-plate and the Optojump system from Gyko-derived data.

Accuracy of PARTwear Inertial Sensor and Optojump Optical Measurement System for Measuring Ground Contact Time During Running

Ammann, R, Taube, W, and Wyss, T. Accuracy of PARTwear inertial sensor and Optojump optical measurement system for measuring ground contact time during running. J Strength Cond Res 30(7): 2057-2063, 2016-The aim of this study was to validate the detection of ground contact time (GCT) during running in 2 differently working systems: a small inertial measurement sensor, PARTwear (PW), worn on the shoe laces, and the optical measurement system, Optojump (OJ), placed on the track. Twelve well-trained subjects performed 12 runs each on an indoor track at speeds ranging from 3.0 to 9.0 m·s. GCT of one step per run (total 144) was simultaneously obtained by the PW, the OJ, and a high-speed video camera (HSC), whereby the latter served as reference system. The sampling rate was 1,000 Hz for all methods. Compared with the HSC, the PW and the OJ systems underestimated GCT by -1.3 ± 6.1% and -16.5 ± 6.7% (p-values ≤ 0.05), respectively. The intraclass correlation coefficients between PW and HSC and between OJ and HSC were 0.984 and 0.853 (p-values < 0.001), respectively. Despite the constant systematic underestimation of GCT, analyses indicated that PW successfully recorded GCT over a wide range of speeds. However, results showed only moderate validity for the OJ system, with increasing errors when speed decreased. In conclusion, the PW proved to be a highly useful and valid application, and its use can be recommended not only for laboratory settings but also for field applications. In contrast, data on GCT obtained by OJ during running must be treated with caution, specifically when running speed changes or when comparisons are made with GCT data collected by other measurement systems.

Vertical Jump Performance of Professional Male and Female Volleyball Players

Vertical jump (VJ) performance is an important element for successful volleyball practice. The aims of the study were (a) to explore the overall VJ performance of elite volleyball players of both sexes, (b) to explore the differences in VJ performance among different competition levels and different playing positions, and (c) to evaluate the sex-related differences in the role of the arm swing and 3-step approach with arm swing on the jump height. We assessed the VJ capacity in 253 volleyball players (113 males and 140 females) from Slovenian first and second Volleyball Division. The height of squat jump (SJ), countermovement jump, block jump, and attack jump was tested using an Optojump system. We observed significant differences (p ≤ 0.05) in VJ height between different levels of play that were most pronounced in the SJ. Position-related differences in VJ performance were observed in male players between receivers and setters (p ≤ 0.05), whereas in females, VJ performance across different playing positions seems equal. Finally, we found that male players significantly better use the arm swing during VJ than females (p ≤ 0.05), whereas the use of eccentric part of the jump and approach before the spike to improve VJ performance seem to be equally mastered activity in both sexes. These results could assist coaches in the development of jumping performance in volleyball players. Furthermore, presented normative data for jump heights of elite male and female volleyball players could be useful in selection and profiling of young volleyball players.

Does Body Fat Affect Performance Indicators in Youth Soccer?

Aims: The study aimed to identify the relationship between body parameters and performance factors for different age groups. Study Design: The researchers recorded the indoor tests (height, weight, body fat, body mass index, and vertical jump) and then they recorded the outdoor tests (sprint, agility, and VO2max). The measurements took place at the beginning of the competitive season. The tests were scheduled under similar conditions of time, light, temperature, and a standardized warm-up. Methodology: 314 Greek young male players aged 7-17 years old participated in the current study. The portable device called the OptoJump System (Microgate, Bolzano, Italy) was used to measure the performance factors of each player. A weighting scale (BC1000, Tanita, Japan) and a cursor were used to measure the body parameters. Results: It was found that body fat and then body mass index were the most important predictors of performance factors. Specifically, body fat was the most important predictor of performance

Changes in temporal parameters during performance of the Step Test in older adults

The purpose of this cross-sectional study was to examine the changes in the temporal parameters measured during the performance of the Step Test, to evaluate the relationship between age and these measurements and to determine their relationships to aerobic endurance, muscular strength and mobility in a sample of older adults. Eighty-eight older adults (mean age=73.0 years, SD=5.4) participated in the study. During the Step Test, we collected measurements of the following temporal parameters using the Optojump system: step number, support time and executive time. We also evaluated the performance of the Six-Minute Walk Test, the 30-Second Chair Rise Test and the Timed Up and Go Test. We observed a significant decrease in the step number and an increase in the support time and executive time (p=.001) during each minute of the test. The results revealed that the relationship between age and Step Test performance was attenuated when we controlled for potential confounding variables. Controlling for age, gender and BMI, variance in support time during the Step Test was accounted for by variance in 30-Second Chair Rise Test performance (partial r=−.224). Moreover, variance in executive time was accounted for by variance in 30-Second Chair Rise Test (partial r=.234) and Timed Up and Go Test performance (partial r=−.259). Understanding the factors that are associated with the performance of the Step Test may provide new insights into the development of specific intervention programmes for older adults.

Does an Abdominal Strengthening Program Influence Leg Stiffness During Hopping Tasks?

According to the spring mass model, leg stiffness (characterized by the measure of kleg) behavior is theoretically dependent on lower limb joint and trunk stiffness. Yet, the influence of the trunk as a possible regulator of kleg is unknown. This study investigated the influence of abdominal training on kleg during hopping tasks. Fourteen young male (age 18.5 ± 0.5 years, height 176.4 ± 4.3 cm, weight 69.9 ± 5.5 kg) soccer players (national level) participated in the study. Two groups (bracing B group, n = 7 vs. hollowing transversus abdominis [TrA] H group, n = 7) with identical training load followed an 8-week training program for abdominal strengthening. Contact time, flight time, jump height, and kleg were measured with an OptoJump system during a standardized hopping task (2.2 Hz) before and after the training program. Results for each group showed that only the H group increased kleg after the intervention (+15.7%) compared with the B group (+5.9%). This difference was explained by a 6.5% decrease in contact time in H group (-2.4% in B) with increased flight time (+8.8% in H vs. +2% in B). A large increase was found for jump height in H (+16.9%) compared with B group (+4.4%). This study showed that TrA strengthening improves leg stiffness in hopping tasks. Our findings suggest the potential role of abdominal muscles in controlling "lumbopelvic" stiffness as a part of the spring according to the spring mass model, and thus influencing kleg by reduced ground contact phase.

Single-Bundle Versus Double-Bundle Anterior Cruciate Ligament Reconstruction: Assessment With Vertical Jump Test

The study was designed to compare the clinical results of traditional single-bundle (SB) anterior cruciate ligament (ACL) reconstruction with those of double-bundle (DB) ACL reconstruction. This study comprised 80 patients aged 18 to 45 years with an isolated ACL lesion: 40 patients underwent SB reconstruction, and 40 patients underwent DB reconstruction. Patients were assessed preoperatively with functional assessment including the International Knee Documentation Committee 2000 knee subjective form and visual analog scale, as well as physical examination (including the pivot-shift test and instrumented knee laxity measurement). Vertical jump assessment with the Optojump system (Microgate, Bolzano, Italy) has been introduced as a method to compare functional ability between the 2 surgical techniques. The same protocol was repeated 6 months, 12 months, and 2 years after surgery. No statistically significant differences were noted between the groups concerning subjective evaluation, thigh girth difference, mean visual analog scale score, range of motion, and Lachman and anterior drawer tests (P= not significant). A statistically higher number of patients in the SB group showed a positive pivot-shift test and a higher side-to-side difference when measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA) than in the DB group (P < .001). Better mean jumping performance results were reported in the DB group compared with the SB group (P < .001). The average performance results for the injured limb were not significantly reduced compared with those of the uninjured limb in the DB group 12 months after surgery. At 2 years, a restoration of jumping ability in the ACL-reconstructed limb was achieved in both groups regardless of the technique used. DB ACL reconstruction has been proven to be superior to the SB technique with regard to knee stability and vertical jump performance. Level II, prospective comparative study.

Changes of Reaction Time and Blood Lactate Concentration of Elite Volleyball Players During a Game

The purpose of this study was to investigate changes in reaction time of elite volleyball players during a game. Fourteen volleyball players participated in the study. Reaction time was measured using the Optojump system. In addition, blood lactate concentration was assessed to monitor physiological load during the game. All measurements were performed during a pre-game test and during sets 1, 2, 3 and 4. Reaction time during set 1 decreased significantly by 13,3 % compared with pre-game values, from 600 ms during the pre-game test to 520 ms during set 1 (p<0,05). Blood lactate concentration increased significantly during set 1, 2, 3 and 4 compared with pre-game conditions (p<0,05). Reaction time stays in the first phase of its changes pattern and elite volleyball players do not reach psychomotor fatigue threshold throughout the game.