Movement adjustments in preparation for single-leg jumps in individuals with functional ankle instability

There is some evidence showing that people with functional ankle instability (FAI) can present changes in postural control during the landing phase of a jump. These studies also show preliminary results indicating possible changes during phases prior to landing. Therefore, the objective of this study was to investigate whether movement adjustments prior to a jump are different between people with and without FAI. Sixty participants with (n = 30) and without (n = 30) FAI participated in this study. The main outcome measures were the variability of range of motion in ankle inversion/eversion and dorsiflexion/plantarflexion; and variability of center of pressure for the directions anterior-posterior and medio-lateral during the pre-jump period for drop jump, vertical jump and during single-leg stance. The group with instability showed more variability of center of pressure in anterior-posterior direction (p = 0.04) and variability of range of motion in ankle dorsiflexion/plantar flexion (p = 0.04) compared to control in the single-leg stance test. For the within-group comparisons, the group with instability showed more variability of center of pressure in anterior-posterior direction in the drop jump higher than single-leg stance and vertical jump. The same pattern was seen for the control group. Thus, this study suggests that people with FAI have greater ankle range of motion variability and center of pressure variability in the anterior-posterior axis when compared to healthy individuals during single-leg stance. For those same two variables, preparation for a drop jump causes more postural instability when compared to the preparation for a vertical jump and to single-leg stance.     

Enhanced retention of drop vertical jump landing technique: A randomized controlled trial

External focus instructions have been shown to result in superior motor performance compared to internal focus instructions. Using an EF may help to optimize current anterior cruciate ligament (ACL) injury prevention programs. The purpose of the current study was to investigate the effects of instructions on landing technique and performance by comparing an external focus (EF), internal focus (IF), video (VI) and control (CTRL) group. Subjects (age 22.50 ± 1.62 years, height 179.70 ± 10.43 cm, mass 73.98 ± 12.68 kg) were randomly assigned to IF (n = 10), EF (n = 10), VI (n = 10) or CTRL group (n = 10). Landing was assessed from a drop vertical jump (DVJ) in five sessions: pretest, two training blocks (TR1 and TR2) and directly after the training sessions (post test) and retention test 1 week later. Group specific instructions were offered in TR1 and TR2. Landing technique was assessed with the Landing Error Scoring System (LESS) and jump height was taken as performance measure. The results show that males in the VI group and females both in the VI and EF groups significantly improved jump-landing technique. Retention was achieved and jump height was maintained for males in the VI group and females both in the VI and EF groups. It is therefore concluded that EF and VI instructions have great potential in ACL injury prevention.     

H-reflex excitability is inhibited in soleus,but not gastrocnemius,at the short-latency response of a horizontal jump-landing task

Impaired spinal-level neuromuscular control is suggested to contribute to instability and injury during dynamic landing tasks. Despite this suggestion, spinal-level neuromuscular control is yet to be examined during a horizontal jump-landing task. The aim of the current study was to assess changes in H-reflexes and its reliability at the short-latency response of landings from short and long distances. Eight healthy individuals (five male, three female; age, 22 ± 1.2 yrs; height, 178 ± 8.1 cm; weight, 72 ± 15.7 kg) participated in the study. H-reflexes were evoked at the SLR in the soleus and medial gastrocnemius muscles, during two landing conditions: 25% and 50% of maximal broad jump distance. H-reflexes were expressed relative to the background electromyography (EMG) and maximal M-wave responses (M-max). Soleus H-reflexes were inhibited when landing from shorter distance (25%, 13.9 ± 7.6%; 50%, 8.3 ± 6.5%; p < 0.01). No change in H-reflex excitability was observed in medial gastrocnemius. Background EMG was unaltered across landing conditions. Inhibition of soleus H-reflex excitability from 25% to 50% landing condition indicates a reduced contribution of Ia-afferent feedback to the alpha-motor neuron during landings from greater distances, which may contribute to stiffness regulation at the ankle joint. Unaltered H-reflex excitability of medial gastrocnemius is most likely attributed to its functional role during the landing task.     

Technique determinants of knee joint loads during cutting in female soccer players

The aim of this study was to investigate the relationships between technique characteristics and knee abduction moments during 90° cuts. A cross sectional design involving 26 elite and sub-elite female soccer players (mean ± SD; age: 21 ± 3.2 years, height: 1.68 ± 0.07 m, and mass: 59.1 ± 6.8 kg) was used to explore relationships between pre-determined technical factors on knee abduction moments during cutting. Three dimensional motion analyses of 90° cuts on the right leg were performed using ‘Qualisys Pro Reflex’ infrared cameras (240 Hz). Ground reaction forces were collected from two AMTI force platforms (1200 Hz) embedded into the running track to examine 2nd last and last footfalls. Pearson’s correlation coefficients, co-efficients of determination and hierarchical multiple regression were used to explore relationships between a range of technique parameters and peak knee abduction moments. Significance was set at p < .05. Hierarchical multiple regression revealed that initial knee abduction angle, lateral leg plant distance and initial lateral trunk lean could explain 67% (62% adjusted) of the variation in peak knee abduction moments (F_(1,22) = 8.869, p = .007). These findings reveal potential modifiable technical factors to lower peak knee abduction moments during cutting.     

Match play demands of 11 versus 11 professional football using Global Positioning System tracking: Variations across common playing formations

This study aimed to examine Global Positioning System (GPS) determined movement patterns across the 5 most common playing formations (4-4-2; 4-3-3; 3-5-2; 3-4-3; 4-2-3-1) employed in 11 versus 11 football match play in England. Elite male footballers (n = 46) were monitored over the course of a season; total distance (TD), high speed running (HSR), high metabolic load distance (HMLD), high speed accelerations (Acc) and decelerations (Dec) data was collected for analysis. It was found that 3-5-2 formation elicited higher TD (10528 ± 565 m, p = 0.05), HSR (642 ± 215 m, p = 0.001), and HMLD (2025 ± 304 m, p = 0.001) than all other formations and above average Acc and Dec (34 ± 7, p = 0.036 and 57 ± 10, p = 0.006), with 4-2-3-1 eliciting the highest Acc and Dec (38 ± 8 and 61 ± 12). Positional data showed that CM in 4-3-3 covered >11% TD than in 4-4-2 (p = 0.012). FW in 3-5-2 covered >45% HSR than in 4-2-3-1 (p = 0.004). CM in 4-3-3 covered >14% HMLD than in 4-4-2 (p = 0.367). FW in 4-3-3 performed >49% accelerations than in 4-2-3-1 (p = 0.293). WD in 3-5-2 performed >20% more decelerations than in 4-4-2 (p = 0.161). This study is important for coaches understanding, that positional physical characteristics are influenced by the demands of playing in different formations during match play.     

The effect of different kick start positions on OMEGA OSB11 blocks on free swimming time to 15 m in developmental level swimmers

The introduction of the OMEGA OSB11 starting blocks (Swiss Timing, Corgémont, Switzerland) which feature an adjustable inclined plate built into the rear of the platform, have led to the evolution of the “kick start” style of swimming start. Previous studies examining the effect of different starting positions using the OSB11 starting blocks have not examined swimming performance over distances beyond 7.5 m. Therefore, the purpose of the current study was to compare three starting positions (front, neutral and rear-weighted) using the kick start to determine whether a given position can improve swimming performance over a 15 m distance. After undergoing four weeks of dive training using each of the three positions, ten developmental level swimmers completed three 20 m sprint trials in each position. Results indicated that the neutral and rear-weighted positions produced faster times to 15 m (p < .01) when compared to the front-weighted position. Starting position did not affect the swimmer’s velocity between 4.5 and 5.5 m or between 14.5 and 15.5 m (p = .50). Developmental level swimmers should choose between a neutral-weighted or rear-weighted position on the new OSB11 starting blocks.     

Contextual effects on activity profiles of domestic field hockey during competition and training

Game context is widely accepted to influence performance but most data available is ‘categorical’ and addresses performance rather than activity. This study assessed direct effects of opposition and team ranking in field hockey to establish influences on activity. One hundred and eight (n = 108) female field hockey players (age 16–39 years) participated, giving 186 competition and 48 training analyses. Team average distance (mean ± SD) observed in a mid-ranked team during competition ranged from 5949 ± 611 to 7719 ± 257 m demonstrating an opposition rank effect (Pearson’s r = .71; adjusted R² = .42). However, multiple linear regression analysis demonstrated a stronger relationship in lower ranked teams (Pearson’s r = .99; adjusted R² = .97 through 3–9). In contrast, no team rank effect was observed during randomly monitored competition where team average distance ranged from 5177 ± 444 to 7316 ± 241 m (Pearson’s r = .15 and adjusted R² = .12). In training, however, a team rank effect was observed in distance-related performance indicators where team average distance during small-sided games ranged from 5877 ± 188 to 3551 ± 193 m drill (per 70 min) with Pearson’s r = .95 and adjusted R² = .87. The presence of contextual effects has significant practical implications for team sports where the training load assumed from competition may be overestimated.     

The effect of swinging the arms on muscle activation and production of leg force during ski skating at different skiing speeds

The study investigated the effects of arm swing during leg push-off in V2-alternate/G4 skating on neuromuscular activation and force production by the leg muscles. Nine skilled cross-country skiers performed V2-alternate skating without poles at moderate, high, and maximal speeds, both with free (SWING) and restricted arm swing (NOSWING). Maximal speed was 5% greater in SWING (P < 0.01), while neuromuscular activation and produced forces did not differ between techniques. At both moderate and high speed the maximal (2% and 5%, respectively) and average (both 5%) vertical force and associated impulse (10% and 14%) were greater with SWING (all P < 0.05). At high speed range of motion and angular velocity of knee flexion were 24% greater with SWING (both P < 0.05), while average EMG of m. biceps femoris was 31% lower (all P < 0.05) in SWING. In a similar manner, the average EMG of m. vastus medialis and m. biceps femoris were lower (17% and 32%, P < 0.05) during the following knee extension. Thus, swinging the arms while performing V2-alternate can enhance both maximal speed and skiing economy at moderate and, in particularly, high speeds.     

Motor actions and spatiotemporal changes by weight divisions of mixed martial arts: Applications for training

This study compared motor actions and spatiotemporal changes between weight divisions from Ultimate Fighting Championship (UFC™), conducting a practical application for mixed martial arts (MMA) training. For this, we analyzed 2814 rounds of all weight divisions by motor actions and spatiotemporal changes according actions and time of the Keeping distance, Clinch and Groundwork combat phases. We observed differences between weight divisions in the keeping distance on stand-up combat (p ≤ 0.001; with lower time in Featherweight 131.4 s and bantamweight 127.9 s) clinch without attack (p ≤ 0.001; with higher timer in Flyweight 11.4 s and Half-middleweight 12.6 s) and groundwork without attack (p ≤ 0.001; with higher timer in Half-middleweight 0.9 s). During keeping distance, half-middleweight presented a higher frequency of Head Strikes Landed (p = 0.026; 7 ± 8 times) and attempted (p = 0.003; 24 ± 22 times). In clinch actions heavyweight present a higher frequency (p ≤ 0.023) of head strike landed (3 ± 7 times) and attempted (4 ± 9 times) and half-middleweight for body strikes (p ≤ 0.023) landed (2 ± 5 times) and attempted (3 ± 5 times). At the last, during groundwork, Bantamweight present a higher frequency (p ≤ 0.036) of head strikes landed (8 ± 10 times) and attempted (10 ± 13 times) body strikes landed (p ≤ 0.044; 3 ± 5 times) and attempted (3 ± 6 times). This study reveals important point to training and provide a challenge applied referential to the conditioning plains. From the weight divisions differences should be aware of the increase in the frequency of distance actions, especially in light and middleweights. On the Ground, bantamweight can focus on striking and grappling actions than others.     

External focus and autonomy support: Two important factors in motor learning have additive benefits

We examined whether the combination of two factors that have consistently been found to enhance motor learning – an external focus (EF) of attention and autonomy support (AS) – would produce additive benefits. Participants practiced throwing with their non-dominant arm. In a 2 × 2 design, they were or were not asked to focus externally (i.e., on the target), and were or were not given a choice (autonomy support). The latter involved choosing 2 5-trials blocks during practice on which they used their dominant arm. All four groups – EF/AS, EF, AS, and C (control) – completed a practice phase consisting of 60 trials. The distance to the target (bull’s eye) was 7.5 m. One day later, participants performed retention (same target distance) and transfer tests (8.5 m). Both external focus instructions and autonomy support enhanced retention and transfer performance. Importantly, the combination of these factors resulted in additive learning advantages. The EF/AS group showed the greatest throwing accuracy, and the EF and AS groups outperformed the C group. In addition, self-efficacy measured after practice and before retention and transfer was increased by both factors. Thus, promoting an external focus of attention and supporting learners’ need for autonomy seem to independently influence learning.     

Relationships between match activities and peak power output and Creatine Kinase responses to professional reserve team soccer match-play

The specific movement demands of soccer that are linked to post-match recovery and readiness to train are unclear. Therefore, we examined the relationship between Global Positioning System (GPS) variables and the change (Δ; from baseline) in Creatine Kinase (CK) concentrations and peak power output (PPO; during the countermovement jump) at 24 h and 48 h post-match. Fifteen English Premier League reserve team players were examined over 1–4 matches. Measurements of CK and PPO were taken before (24 h prior to match-play) and after (+24 h and +48 h) each game during which movement demands were quantified using 10 Hz GPS data. High intensity distance covered (r = 0.386, p = 0.029; r = −0.349; p = 0.050), high intensity distance covered⋅min⁻¹ (r = 0.365, p = 0.040; r = −0.364, p = 0.040), high speed running distance (r = 0.363, p = 0.041; r = −0.360, p = 0.043) and the number of sprints⋅min⁻¹ (r = 0.410, p = 0.020; r = −0.368, p = 0.038) were significantly related to ΔCK and ΔPPO at +24 h post-match, respectively. No relationships were observed between any match variables and ΔCK and ΔPPO after +48 h of recovery. These findings highlight that high intensity match activities are related to ΔCK and ΔPPO in the 24 h, but not 48 h, following soccer match-play. Such information is likely of interest to those responsible for the design of soccer player’s training schedules in the days following a match.     

Muscle strength and functional performance is markedly impaired at the recommended time point for sport return after anterior cruciate ligament reconstruction in recreational athletes

PurposeTo examine potential deficits in muscle strength or functional capacity when comparing (1) an ACL reconstructed group to matched healthy controls, (2) the ACL reconstructed leg to the non-injured leg and (3) the non-injured leg to matched healthy controls, at the time-point of recommended sport return 9–12 months post-surgery.MethodsSixteen patients (male-female ratio: 9:7) 9–12 months post ACL reconstruction and sixteen age and sex matched healthy controls were included. Outcome measures included maximal knee extensor (KE) and knee flexor (KF) dynamometry, including measurement of rate of force development, functional capacity (counter movement jump (CMJ) and single distance hop (SDH)) and the Lysholm score.ResultsCompared to the control group, maximal KE and KF muscle strength were impaired in the ACL reconstructed leg by 27–39% and 16–35%, respectively (p < .001). Also, impairments of both CMJ (38%) and SDH (33%) were observed (p < .001). Rate of force development for KE were reduced in the ACL group compared to the control group (p < .001). Similarly, the KE and KF muscle strength, CMJ and SDH of the ACL reconstructed leg were impaired, when compared to the non-injured leg by 15–23%, 8–20%, 23% and 20%, respectively (p < .05).ConclusionMuscle strength and functional capacity are markedly impaired in the ACL reconstructed leg of recreationally active people 9–12 months post-surgery when compared to healthy matched controls and to their non-injured leg. This suggests that objective criteria rather than “time-since-surgery” criteria should guide return to sport.     

Illegal crossing behavior of pedestrians at signalized intersections: Factors affecting the gap acceptance

Purpose of designing crosswalks is to allow pedestrians to cross the roads safely avoiding conflicts between pedestrians and motorized vehicles. However, pedestrians do not always comply with the crossing rules, whether it is timing (signalization) and/or location (crossing facility). An observation survey of illegal crossings was conducted at six intersections in Izmir, Turkey to determine the distance and time gap perception of the pedestrians for safe road-crossing within the 25 m of the crosswalk. Each intersection was observed on weekdays during afternoon (12.30–13.30) and evening peak hours (17.00–18.00). Totally, 444 illegal crossings were observed at all intersections. Data were analyzed playing the video recordings in office. All roads were consisted of two lanes. In this study pedestrians’ illegal crossing behavior at signalized intersections depending on the position of the oncoming vehicle is of interest. Safety margins and crossing times of the pedestrians were also reported. Position of the vehicle was determined for the first lane at the instant the pedestrian stepped the lane. Pedestrians’ distance gap perception was categorized into five groups depending on the position of the oncoming vehicle which are; vehicle is within the 25 m of the crosswalk, vehicle is within the 25–50 m of the crosswalk, vehicle is within the 50–75 m of the crosswalk, vehicle is just beyond 75 m, and vehicle is out of field of view. Factors affecting the distance gaps, safety margins and crossing times were analyzed by ANOVA. The most significant effect was the vehicle speed in all analysis. Pedestrians based their decision of crossing on distance rather than time gap.     

Breastfeeding and motor development: A longitudinal cohort study

BackgroundWhile there is a large body of work supporting the importance of early feeding practices on cognitive, immunity, behavioural and mental outcomes, few longitudinal studies have focused on motor development. The relationship between duration of breast feeding and motor development outcomes at 10, 14, and 17 years were examined.MethodsData were obtained from the Western Australian Pregnancy (Raine) Study. There were 2868 live births recorded and children were examined for motor proficiency at 10 (M = 10.54, SD = 2.27), 14 (M = 14.02, SD = 2.33) and 17 (M = 16.99, SD = 2.97) years using the McCarron Assessment of Neuromuscular Development (MAND). Using linear mixed models, adjusted for covariates known to affect motor development, the influence of predominant breast feeding for <6 months and ⩾6 months on motor development outcomes was examined.ResultsBreast feeding for ⩾6 months was positively associated with improved motor development outcomes at 10, 14 and 17 years of age (p = 0.019, β 1.38) when adjusted for child’s sex, maternal age, alcohol intake, family income, hypertensive status, gestational stress and mode of delivery.ConclusionEarly life feeding practices have an influence on motor development outcomes into late childhood and adolescence independent of sociodemographic factors.     

Analysis of rainfall impacts on platooned vehicle spacing and speed

This paper investigates the impact of rainfall on the behavior of drivers in a car-following state by analyzing the differences in time gap, speed, and following distance of platooned vehicles between no-rain and rainy weather conditions on a two-lane rural state highway. Time gap, following distance, and individual vehicle speed were observed. Platooned vehicles were identified by a maximum time gap threshold of 4 s, allowing for interactions between vehicles beyond perception–reaction time. Rainfall intensity was utilized as the measure of local precipitation conditions and was categorized according to American Meteorological Society standards. The analysis showed that rainy weather conditions were strongly correlated with greater spread in speed distributions when compared to dry conditions. Further, the shift from no-rain to rain showed an increase in time gap and a reduction in speed. No statistically significant differences were observed between following distances in any weather conditions – suggesting that drivers tend to maintain following distance irrespective of weather conditions and speed reduction causes the observed time gap increase. This is supported by the observed 5.6% decrease in mean time gap – from 1.97 s to 2.1 s and the 3.7% decrease in mean speed – from 47 mph (75.6 km/h) to 45.3 mph (72.9 km/h).     

Different coordination and flexibility of the spine and pelvis during lateral bending between young and older adults

This study examined coordination of the spine and pelvis during lateral bending of the trunk in older adults. Thirty-four healthy subjects (17 young and 17 older adults) demonstrated lateral bending at a controlled speed while holding a bar at approximately 180 degrees of shoulder flexion. Kinematic data collection was completed on the thoracic spine, lumbar spine, and pelvis. The coupling angle was calculated to examine the thorax–lumbar, lumbar–pelvis, and thorax–pelvis coordination patterns. The older adults demonstrated a reduced range of motion (ROM) of the lumbar spine, while both groups revealed similar ROM in the thorax and in the pelvis. The coupling angle between the straightening and bending phases was different only for the older adults in the thorax–lumbar (23.4 ± 8.0 vs. −1.6 ± 4.4, p = 0.004) and the lumbar–pelvis (65.4 ± 7.2 vs. 86.1 ± 7.8, p = 0.001) coordination. However, there was no group difference in the thorax–pelvis coordination. These findings indicate that age-related changes in the lumbar region affect coordination patterns only during the bending phase. The older adults preserved a similar pattern of movement to the young adults during the straightening phase, but the coordination variability of the coupling angles was greater for the older adults than for the young adults. This movement pattern suggests that the older adults lacked consistent trunk control in an attempt to optimize lateral bending coordination.     

Effects of different swimming race constraints on turning movements

The aim of this study was to investigate the effects of different swimming race constraints on the evolution of turn parameters. One hundred and fifty-eight national and regional level 200-m (meters) male swimming performances were video-analyzed using the individualized-distance model in the Open Comunidad de Madrid tournament. Turn (p < .001, ES = 0.36) and underwater distances (p < .001, ES = 0.38) as well as turn velocity (p < .001, ES = 0.69) significantly dropped throughout the race, although stroke velocity and underwater velocity were maintained in the last lap of the race (p > .05). Higher expertise swimmers obtained faster average velocities and longer distances in all the turn phases (p < .001, ES = 0.59), except the approach distance. In addition, national level swimmers showed the ability to maintain most of the turn parameters throughout the race, which assisted them in improving average velocity at the end of races. Therefore, the variations in the turning movements of a swimming race were expertise-related and focused on optimizing average velocity. Turning skills should be included in the swimming race action plan.     

An especial skill in elite wheelchair basketball players

We aimed to investigate whether an especial skill is present in elite wheelchair basketball players when taking twenty shots with a regular basketball from five different distances (11 ft, 13 ft, 17 ft, & 19 ft) from the basket including the free throw line (15 ft). Twelve elite male basketball players participated. The results showed that as distance increased shot accuracy decreased in line with force by variability predictions for the 11 ft, 13 ft, 17 ft, & 19 ft distances. However, shot performance at the free throw line where players are more familiar with practicing free throw shots did not follow this trend. A linear regression line was drawn to predict performance at the free throw line based on nearer (11 ft & 13 ft) and farer (17 ft & 19 ft) distances to the basket, this was then compared to actual performance. A significant difference between actual and predicted scores was found (p < .05) supporting the presence of an especial skill. Significant positive correlations were found for the 11 ft and 17 ft distance, age, years of playing, and accumulated practice hours with performance at the 15 ft line (p < .05). These correlations imply the operation of generalization in the especial skill. This observation received support from applying a model in which shot accuracy as a function of distance was approximated by two regression lines.     

Force-displacement differences in the lower extremities of young healthy adults between drop jumps and drop landings

We measured ground reaction force and lower extremity shortening in ten healthy, young adults in order to compare five trials of drop jumps to drop landings. Our dependent variable was the percentage of displacement (shortening) between the markers on the ASIS and second metatarsal heads on each LE, relative to the maximum shortening (100% displacement) for that trial at the point of greatest ground reaction force. We defined this as “percent displacement at maximum force” (%d_Fmax). The sample mean %d_Fmax was 0.73% ± 0.14% for the drop jumps, and 0.47% ± 0.09% for the drop landings. The mean within-subject difference score was 0.26% ± 0.20%. Two-tailed paired t test comparing %d_Fmax between the drop jump and drop landing yielded P = 0.002. For all participants in this study, the %d_Fmax was greater in drop jumps than in drop landings. This indicates that in drop jumps, the point of maximum force and of maximum shortening was nearly simultaneous, compared to drop landings, where the point of maximum shortening followed that of maximum force by a greater proportion. This difference in force to displacement behavior is explained by linear spring behavior in drop jumps, and linear damping behavior in drop landings.