Laura Smith

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.

The effect of unstable sandals on instability in gait in healthy female subjects.

Unstable footwear generally lacks thorough peer-review published research to support concepts and marketing claims. The purpose of this study was to investigate the instability induced by four (FitFlop, Masai Barefoot Technology, Reebok Easy-Tone and Skechers Tone-Ups) commercially available unstable sandals and one stable control sandal (Earth) in walking in 15 females (mean±SD age was 29±6.7 years, mass 62.6±6.9kg and height 167.1±4.2cm). Three-dimensional motion with synchronised electromyography and kinetic data were collected. Walking speed and step length remained consistent between conditions, however double support time decreased in Masai Barefoot Technology. Centre of pressure data identified no consistent difference between the stable control and the unstable sandals, however Masai Barefoot Technology reduced the anterior-posterior range of centre of pressure. Muscle activity differed significantly at the ankle in the unstable footwear. FitFlop, Reebok and Skechers increased peroneal activity during pre-swing, whereas Masai Barefoot Technology increased medial gastrocnemius and decreased tibialis anterior activity in loading response and mid-stance. The larger rocker sole of the Masai Barefoot Technology altered gait and muscle activation with regard to braking and progression in the sagittal plane. Reebok, Skechers and FitFlop, with softer, less stable foreparts increased evertor action at toe-off, having their effect in the coronal plane. The study highlighted that any instability induced by the shoes is design-specific.

A comparison of kinematic algorithms to estimate gait events during overground running

The gait cycle is frequently divided into two distinct phases, stance and swing, which can be accurately determined from ground reaction force data. In the absence of such data, kinematic algorithms can be used to estimate footstrike and toe-off. The performance of previously published algorithms is not consistent between studies. Furthermore, previous algorithms have not been tested at higher running speeds nor used to estimate ground contact times. Therefore the purpose of this study was to both develop a new, custom-designed, event detection algorithm and compare its performance with four previously tested algorithms at higher running speeds. Kinematic and force data were collected on twenty runners during overground running at 5.6m/s. The five algorithms were then implemented and estimated times for footstrike, toe-off and contact time were compared to ground reaction force data. There were large differences in the performance of each algorithm. The custom-designed algorithm provided the most accurate estimation of footstrike (True Error 1.2 ± 17.1 ms) and contact time (True Error 3.5 ± 18.2 ms). Compared to the other tested algorithms, the custom-designed algorithm provided an accurate estimation of footstrike and toe-off across different footstrike patterns. The custom-designed algorithm provides a simple but effective method to accurately estimate footstrike, toe-off and contact time from kinematic data.

Kinematic variations due to changes in pace during men's and women's 5 km road running

The purpose of this study was to investigate variations in kinematic parameters in mens and womens 5 km road racing. Athletes often vary their pace and changes particularly tend to occur towards the end of a race due to fatigue and sprint finishes. Twenty competitive distance runners (10 male, 10 female) were videoed as they completed the English National 5 km championships. Three-dimensional kinematic data were analysed using motion analysis software (SIMI, Munich). Data were recorded at 950 m, 2,400 m and 3,850 m. Repeated measures ANOVA showed significant decreases in speed due to reduced step length and cadence in both men and women. These decreases predominantly occurred between the first two measurement points. The hip, knee, ankle and shoulder angles at both initial contact and toe-off did not change significantly, but there were significant reductions in the elbow angle for both men (at initial contact) and women (at toe-off).

Footstep Manipulation during Uphill Running

The present study investigated the effects of step frequency manipulation during training on slopes (2%) on biomechanical parameters at Iso-Efficiency Speed (without increasing the metabolic demand). 24 male marathon runners were randomly allocated to one of 2 training groups for 3 weeks: step frequency manipulation group (SFM, n=12) and free step frequency group (SFF, n=12). Lower limb kinematic parameters were measured before and after the 3 weeks training. The SFM group increased step length 4.30% (p<0.001), flight time 29.48% (p<0.001) and decreased contact time 14% (p<0.01). These findings coincide with characteristics of better running performances. The SFF group did not elicit such results. The results from the study could help coaches to devise training methods which could improve an athletes performance through increasing step length. The method provided may aid faster race times for athletes.

Electromyographic analysis of shoulder muscles during press-up variations and progressions.

Due to the versatility of the press-up it is a popular upper extremity strengthening and rehabilitation exercise. Press-up programmes are often progressed by increasing weight-bearing load and using unstable bases of support. Despite the popularity of the press-up research examining press-up variations is limited. The aim of the study was to examine the influence of common press-up exercises on serratus anterior, infraspinatus, anterior deltoid, pectoralis major and latissimus dorsi muscles overall EMG activity. Twenty-one healthy individuals participated in this study. Surface electrodes were placed on pectoralis major, anterior deltoid, infraspinatus, serratus anterior and latissimus dorsi muscles. Participants were tested under 7 static press-up conditions that theoretically progressively increase weight-bearing load and proprioceptive challenge while surface electromyographic activity was recorded. There was a high correlation between increased weight-bearing load and increased EMG activity for all muscles in stable base conditions. The introduction of the unstable base conditions resulted in an activation decline in all muscles. Within the two-armed press-up the Swiss ball resulted in decreased activation in all muscles except pectoralis major. Serratus anterior demonstrated the greatest activation as a percentage of maximum isometric contraction across all exercises. The findings of this study indicate that by varying the weight-bearing load and base of support whilst in the press-up position results in significantly different demands on shoulder and scapula muscles.

Joint Kinetics and Kinematics During Common Lower Limb Rehabilitation Exercises

CONTEXT Unilateral body-weight exercises are commonly used to strengthen the lower limbs during rehabilitation after injury, but data comparing the loading of the limbs during these tasks are limited. OBJECTIVE To compare joint kinetics and kinematics during 3 commonly used rehabilitation exercises. DESIGN Descriptive laboratory study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 9 men (age = 22.1 ± 1.3 years, height = 1.76 ± 0.08 m, mass = 80.1 ± 12.2 kg) participated. INTERVENTION(S) Participants performed the single-legged squat, forward lunge, and reverse lunge with kinetic data captured via 2 force plates and 3-dimensional kinematic data collected using a motion-capture system. MAIN OUTCOME MEASURE(S) Peak ground reaction forces, maximum joint angles, and peak sagittal-joint moments. RESULTS We observed greater eccentric and concentric peak vertical ground reaction forces during the single-legged squat than during both lunge variations (P ≤ .001). Both lunge variations demonstrated greater knee and hip angles than did the single-legged squat (P < .001), but we observed no differences between lunges (P > .05). Greater dorsiflexion occurred during the single-legged squat than during both lunge variations (P < .05), but we noted no differences between lunge variations (P = .70). Hip-joint moments were greater during the forward lunge than during the reverse lunge (P = .003) and the single-legged squat (P = .011). Knee-joint moments were greater in the single-legged squat than in the reverse lunge (P < .001) but not greater in the single-legged squat than in the forward lunge (P = .41). Ankle-joint moments were greater during the single-legged squat than during the forward lunge (P = .002) and reverse lunge (P < .001). CONCLUSIONS Appropriate loading progressions for the hip should begin with the single-legged squat and progress to the reverse lunge and then the forward lunge. In contrast, loading progressions for the knee and ankle should begin with the reverse lunge and progress to the forward lunge and then the single-legged squat.

The effect of unstable sandals on single-leg standing

Purpose: Unstable footwear lacks peer-review published research to support concepts and claims. The present study was therefore undertaken to quantify and compare the effect of commercially available unstable sandals on single-leg balance in a healthy female population. Methods: Fifteen participants stood on their right-leg in one control sandal (Earth) and four sandals that are marketed as unstable footwear (FitFlop, Masai Barefoot Technology, Reebok Easy-Tone and Skechers Tone-Ups). Centre of pressure trajectory, lower limb kinematics and lower limb muscle activation were recorded as participants undertook three 30 second trials in each sandal. Results: The unstable sandals altered parameters related to stability in participants. Namely Masai Barefoot Technology increased centre of pressure range in the anterior-posterior direction and concurrently increased sagittal ankle motion. Reebok Easy-Tone had a similar effect in the coronal plane at the ankle. Muscle activation increased in the unstable sandals, with significant differences apparent in the medial gastrocnemius, soleus and rectus femoris, predominantly in Masai Barefoot Technology. Findings were attributed to the large rocker sole on the Masai Barefoot Technology sandal and more subtle outsole designs in the other sandals. Conclusions: Overall minimal differences from the control sandal were evident and it is expected that dynamic tasks may elicit greater differences in stability. The instability imposed by the sandals is design-specific and consideration should be given to this when the footwear is recommended to specific individuals.

Single-leg balance in “instability” footwear

Background The concept of instability footwear is to reduce stability, increase muscle activation and “tone”. Recently numerous brands have developed instability footwear for significant sales. Despite extensive marketing claims there are few empirical studies quantifying effects of instability footwear on muscle activity or motion in healthy individuals aside from Masai Barefoot Technology (MBT) [1,2]. The aim of the study was to quantify instability in single-leg standing in a variety of commercially available instability sandals.

D2.S2.5(3). Changing pivoting technique reduces knee valgus moments : taken from Day 2. Free Communications – Biomechanics and Motor Behaviour

Knee pads are used by volleyball athletes to protect against direct impact injuries when falling. Despite debate as to whether knee pads restrict movement, and therefore affect performance, it has never been explored scientifically. This study aimed to assess the kinematic effect of knee pads on volleyball movements and compare two styles of knee pads in order to identify any differences. With institutional ethics approval 26 volleyball athletes were recruited for the study, 12 male (age 21 ± 1.9 years, height 182.4 ± 8.0 cm and mass 81.5 ± 18.7 kg) and 14 female (age 20.7 ± 1.4 years, height 167.9 ± 7.9 cm and mass 60.5 ± 7.2 kg). Rucanor® Smash and McDavidTM Ultra knee pads were assessed. Bare knees and each pad were compared using Vicon© Nexus and lower body labelling during running, squatting and an outside hit (approach sequence, jump and land). Results displayed that both types of knee pad affect movement; however, during the outside hit, McDavid pads were found to cause greater changes. Knee flexion was reduced during landing from an outside attack hit when knee pads were worn. On the right knee, bare knees allowed 75.10°, Rucanor only 67.28° (difference of 7.8°, P < 0.020) and McDavid only 62.32° (difference of 12.8°, P < 0.001). On the left knee, bare knees allowed 77.75° flexion, McDavid only 66.52° (difference of 11.2°, P < 0.001) and there was no significant difference with Rucanor. An increase in abduction of the foot and an increase in internal rotation at the hip is also seen when knee pads are worn during all movements. It has been previously found (Bisseling et al., 2007, British Journal of Sports Medicine, 41, e8–e8; Bisseling et al., 2008, British Journal of Sports Medicine, 42(6), 483–489) that reduced knee flexion on landing increases the risk of patellar tendinopathy. The current study found knee pads to alter an athlete’s positioning to increase risk of non-contact ACL injury, as described by Ireland (1999, Journal of Athletic Training, 34(2), 150–154). Players at a higher risk for patellar tendinopathy and non-contact ACL injury (those that regularly jump) should not wear knee pads to reduce their risk of injury. However, if an athlete wears knee pads they should consider wearing them consistently to allow their play to adapt, allowing them to make the most of their ability, despite potentially hindering their movement. Knee pad design should be improved to allow protection on impact without impairing an athlete’s movement.