Cameron J Wilson

Basic gait and symmetry measures for primary school-aged children and young adults whilst walking barefoot and with shoes

This study investigated the basic spatio-temporal gait measures of 898 primary school-aged children (5-13 years) and 82 young adults (18-27 years). Participants completed 6-8 walks at preferred speed along a GAITRite walkway whilst barefoot and whilst wearing athletic shoes or runners. Outcome measures (non-normalized and normalized) were gait speed, cadence, step and stride length, support base, single and double support, stance duration, foot angle and associated symmetry measures. Non-normalized measures of speed, step and stride length, support base and foot angle increased with age whereas cadence reduced. Normalized measures remained unchanged with age in children whereas the young adults (both conditions) exhibited a 2.3% reduction in single support, a 5.1% increase in double support and a 2.6% increase in stance duration (p<0.0001). For the entire sample, shoes increased walking speed by 8 cm s(-1), step length by 5.5 cm, stride length by 11.1 cm and base of support by 0.5 cm. In contrast, foot angle and cadence reduced by 0.1 degrees and 3.9 steps min(-1) respectively. Shoes increased both double support (1.6%) and stance time (0.8%), whereas single support reduced by 0.8%. Symmetry remained unaffected by age. On average, measures of step and stride symmetry (combining both conditions) fell around 0.7 cm, whereas measures of symmetry for step and stance time, single and double support fell around 0.6%. Footwear significantly affected gait (p<0.0001). Gait may not be mature by age 13. Gait is symmetrical in healthy children and young adults but may change with pathology.

Basic gait and symmetry measures for primary school-aged children and young adults. II: Walking at slow, free and fast speed

This study recorded basic gait data from 656 healthy primary school-aged children (5-13 years) and 81 young adults (18-27 years) whilst walking over-ground across a level walkway at varying speed. It investigated the effect of gait speed and re-examined the issue of gait maturation. Participants completed 6-8 walks at self-selected slow, free and fast speed along a GAITRite walkway whilst wearing athletic shoes. Outcome measures (non-normalized and normalized) were gait speed, cadence, step and stride length, step and stride time, support base, single and double support (%), stance duration (%), foot angle and associated symmetry measures. Compared to free speed, participants walked 24% slower for the slow speed and 30% faster for the fast speed (p<0.0001). Both normalized and non-normalized measures of cadence, step and stride length increased with speed (p<0.001) whereas step and stride time reduced (p<0.001). As a percentage of the gait cycle, single support and stance duration increased with speed (p<0.001) whereas double support reduced (p<0.001). Foot angle was significantly less (less toe-out) for the fast speed than the free and slow speeds (p<0.001) whereas support base was unaffected by speed. Symmetry measures were unaffected by age or speed. Step and stride symmetry differentials (combining conditions) fell around 0.8 cm, whereas symmetry differentials for step and stance time, single and double support fell around 0.7%. This information can be used by clinicians and researchers to assess the gait of children.

Inconsistent use of terminology in whole body vibration exercise research

Whole body vibration exercise (WBV) intensity can be manipulated by altering the frequency of oscillations and/or its magnitude. The inconsistencies and inaccuracies reported within the literature that at times challenge the replication and advancement of whole body vibration exercise research are discussed. Although frequency is regularly reported, inconsistency exists with the definition of vibration amplitude which has been interchangeably used with other terminology by some researchers. Of primary concern is the risk of injury to participants in future research. Researchers using intensities that were incorrectly reported by previous studies may unwittingly expose participants to harmful intensities. For clarity, an argument is put forward for the standardisation of terminology and reporting of whole body exercise parameters.

Reviewing current knowledge in snatch performance and technique : The need for future directions in applied research

This is a review of current research trends in weightlifting literature relating to the understanding of technique and its role in successful snatch performance. Reference to the world records in the snatch from the 1960s onwards indicates little progress across all weight categories. With such mediocre advances in performance at the International level, there is a need to better understand how snatch technique can improve performance even if only by a small margin. Methods of data acquisition for technical analysis of the snatch have involved mostly 2-dimensional barbell and joint kinematics. Although key variables which play a role in the successful outcome of a snatch lift have been heavily investigated, few studies have combined variables relating both the barbell and the weightlifter in their analyses. This suggests the need for a more detailed approach integrating both barbell-related and weightlifter-related data to enhance understanding of the mechanics of a successful lift. Currently, with the aid of technical advances in motion analysis, data acquisition, and methods of analysis, a more accurate representation of the movement can be provided. Better ways of understanding the key characteristics of technique in the snatch could provide the opportunity for more effective individualized feedback from the coach to the athlete, which should in turn lead to improved performance in competition.

Using three-dimensional kinematics to identify feedback for the Snatch: a case study.

Ho, KWL, Williams, MD, Wilson, CJ, and Meehan, DL. Using three-dimensional kinematics to identify feedback for the snatch: a case study. J Strength Cond Res 25(10): 2773–2780, 2011—This case study evaluated the importance of peak bar velocity and starting posture adopted by a novice weightlifter to the outcome of a Snatch lift. Multiple observations of both successful and unsuccessful attempts were captured using 3D motion analysis (VICON MX: 500 Hz). The following data analysis was then used to derive feedback. In total, 133 attempts of loads ranging from 75 to 100% of 1 repetition maximum (1RM) were performed by the subject (age = 25 years, stature = 171 cm, mass = 74.8 kg, Snatch 1RM = 80 kg). Variables included peak bar velocity, pelvis, hip, knee and ankle joint angles at the starting position for the right side and the difference between (left minus right) sides. No main effects for load, success, or their interactions were found for peak bar velocity. Starting position kinematics were mostly nonsignificant between the outcome of Snatch attempts. Right ankle joint angle was the only exception, where unsuccessful attempts displayed greater (p = 0.0228) dorsiflexion. A more comprehensive finding was achieved through the partition modeling; this analysis provided valuable insight and coaching feedback for the subject in relation to his lower body kinematics at the starting position. Furthermore, the accuracy of this feedback was verified using a holdback data set. Specifically, anterior pelvic tilt (>17.6°) and hip joint (<89.6°) angle were identified as the key features to increasing the likelihood of success. In conclusion, this case study outlines a method of data collection and analysis to assist coaching feedback for an individual.

Outcome and Process in Motor Performance: A Comparison of Jumping by Typically Developing Children and Those with Low Motor Proficiency

The motivation for this study was to explore a conceptual framework to understand the outcomes and processes of motor performance in children. Vertical jumping, a fundamental movement skill, was used to compare children (ages 6–12 years) who were typically developing (TD) and those identified as having low motor proficiency (LMP). Jumps were analysed using force plate and 2D kinematic data. The hierarchal framework was applied starting with jump height and descending to the spatial and timing data that describe the global and local coordination processes. Children with LMP jumped lower than their TD peers. Of most interest for understanding the coordination, peak VCOM occurred earlier in the jumping movement for the LMP group. This is interpreted as coordination error and supported by reduced shank angular velocity immediately prior to take-off. These findings suggest a potential value for the vertical jump as a means for identifying coordination dysfunction in children.

Snatch trajectory of elite level girevoy (Kettlebell) sport athletes and its implications to strength and conditioning coaching

Girevoy sport (GS) has developed only recently in the West, resulting in a paucity of English scientific literature available. The aim was to document kettlebell trajectory of GS athletes performing the kettlebell snatch. Four elite GS athletes (age = 29–47 years, body mass = 68.3–108.1 kg, height 1.72–1.89 m) completed one set of 16 repetitions with a 32.1 kg kettlebell Trajectory was captured with the VICON motion analysis system (250 Hz) and analysed with VICON Nexus (1.7.1). The kettlebell followed a ‘C’ shape trajectory in the sagittal plane. Mean peak velocity in the upwards phase was 4.03 ± 0.20 m s−1, compared to 3.70 ± 0.30 m s−1 during the downwards phase, and mean radial error across the sagittal and frontal planes was 0.022 ± 0.006 m. Low error in the movement suggests consistent trajectory is important to reduce extraneous movement and improve efficiency. While the kettlebell snatch and swing both require large anterior-posterior motion, the snatch requires the kettlebell to be held stationary overhead. Therefore, a different coaching application is required to that of a barbell snatch.

Gait Symmetry in School-Aged Children and Young Adults Whilst Walking at Slow, Normal and Fast Speeds

This investigation recorded normative or reference gait symmetry data. The gait patterns of a large sample of healthy primary school-aged children and young adults were recorded whilst walking along a level walkway with shoes at varying speed. The effect of age and walking speed on gait symmetry was investigated. A sample of 737 healthy able-bodied children (5 to 13 yrs) and 82 young adults (19.6 ± 1.6 yrs) participated in this study. Each participant wore athletic shoes or runners and completed 6 to 8 walks across a GAITRite mat (80 Hz) at self-selected slow, free and fast speeds. Gait parameters extracted were step and stride length, stance duration, step time, swing time, single support and double support. Temporal measures were normalized to the gait cycle. Symmetry measures were calculated from these gait parameters. Symmetry was found to be unaffected by speed or age. Step and stride symmetry differentials (combining conditions) fell around 0.8 cm, whereas symmetry differentials (combining conditions) for stance duration, step time, swing time, single support and double support fell around 0.7%. This shows that gait is highly symmetrical in healthy children and young adults. This appears to be an invariant quality of human gait but may change with pathology.

Reliability of the Ekblom Soccer-specific Endurance Test

Williams, MD, Wiltshire, HD, Lorenzen, C, Wilson, CJ, Meehan, DL, and Cicioni Kolsky, DJ. Reliability of the Ekblom soccer-specific endurance test. J Strength Cond Res 23(5): 1378-1382, 2009-The aim of this study was to explore and quantify measurement reliability of the Ekblom endurance test. Experienced university soccer players (n = 19; age = 20.5 ± 2.5 years; mass = 80.4 ± 9.8 kg; and stature = 179.0 ± 6.0 cm) completed the Ekblom endurance test on 3 separate occasions. Time to complete trial 1 (549 ± 26 seconds) and trial 2 (547 ± 26 seconds) was analyzed, and despite no significant difference (F1,18 = 4.119, p = 0.057, &eegr;P2 = 0.186) between trials, some evidence of systematic bias was observed in the data. Therefore, trial 2 data were compared with those of trial 3 (548 ± 27 seconds), with trial 1 data removed. The subsequent analysis (F1,18 = 0.740, p = 0.401, &eegr;P2 = 0.039) showed a reduction in the risk of making a type II error when compared with the previous analysis. From the reliability analyses (3,1 intraclass correlation = 0.983, SEM = ±3 seconds, smallest worthwhile change = 5 seconds, standard error of prediction [95% confidence intervals] = ± 9 seconds), a high level of measurement reliability was observed and the sensitivity of the test to monitor changes was “good.” In summary, it was shown that a test that involves a variety of soccer-specific forms of locomotion can be highly reliable and sensitive to detect change. In light of the systematic bias found, we do, however, recommend a familiarization session to be scheduled before the introduction of this test.

External kinetics of the kettlebell snatch in amateur lifters

Background Kettlebell lifting has gained increased popularity as both a form of resistance training and as a sport, despite the paucity of literature validating its use as a training tool. Kettlebell sport requires participants to complete the kettlebell snatch continuously over prolonged periods of time. Kettlebell sport and weightlifting involve similar exercises, however, their traditional uses suggest they are better suited to training different fitness qualities. This study examined the three-dimensional ground reaction force (GRF) and force applied to the kettlebell over a 6 min kettlebell snatch set in 12 kettlebell-trained males. Methods During this set, VICON was used to record the kettlebell trajectory with nine infrared cameras while the GRF of each leg was recorded with a separate AMTI force plate. Over the course of the set, an average of 13.9 ± 3.3 repetitions per minute were performed with a 24 kg kettlebell. Significance was evaluated with a two-way ANOVA and paired t-tests, whilst Cohen’s F (ESF) and Cohen’s D (ESD) were used to determine the magnitude. Results The applied force at the point of maximum acceleration was 814 ± 75 N and 885 ± 86 N for the downwards and upwards phases, respectively. The absolute peak resultant bilateral GRF was 1,746 ± 217 N and 1,768 ± 242 N for the downwards and upwards phases, respectively. Bilateral GRF of the first and last 14 repetitions was found to be similar, however there was a significant difference in the peak applied force (F (1.11) = 7.42, p = 0.02, ESF = 0.45). Unilateral GRF was found have a significant difference for the absolute anterior–posterior (F (1.11) = 885.15, p < 0.0001, ESF = 7) and medio-lateral force vectors (F (1.11) = 5.31, p = 0.042, ESF = 0.67). Discussion Over the course of a single repetition there were significant differences in the GRF and applied force at multiple points of the kettlebells trajectory. The kettlebell snatch loads each leg differently throughout a repetition and performing the kettlebell snatch for 6 min will result in a reduction in peak applied force.