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Sports biomechanics [journal]
- Teaching practices of the undergraduate introductory biomechanics faculty: a North American survey. [Journal Article]
- Sports Biomech 2012 Nov; 11(4):542-58.
Instruction and assessment strategies of undergraduate introductory biomechanics instructors have yet to be comprehensively examined. The purpose of this study was to identify the current instruction and assessment practices of North American undergraduate introductory biomechanics instructors and equipment needed for effective instruction in lecture and laboratory sessions. One hundred and sixty-five respondents (age: 42.5 +/- 10.3 years) who currently teach or have taught an introductory biomechanics course in North America were recruited by electronic mail. Subjects completed a web-based survey, consisting of 60 open- and closed-ended questions. Pearson's correlation coefficients were used to assess relationships between instructor's familiarity with either the Biomechanics Concept Inventory or the NASPE Guidelines for Undergraduate Biomechanics, and instructor and course characteristics (number of years teaching, age, faculty rank, number of quizzes given, etc.) A number of variables were significantly (p < 0.05) correlated. Answers to open-ended questions were processed using content analysis, with results categorized in content areas including: instructor and course characteristics; lecture instruction; assessment and equipment; laboratory instruction; assessment and equipment; and instructor's perspectives. Many active learning strategies for lecture and laboratory instruction were identified by faculty. Limited student preparation and limited resources were noted as the instructor's most common challenges.
- Considerations of force plate transitions on centre of pressure calculation for maximal velocity sprint running. [Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Validation Studies]
- Sports Biomech 2012 Nov; 11(4):532-41.
The aims of this study were to evaluate the accuracy of centre of pressure (COP) data obtained during transition of load across the boundary between two force plates, and secondly to examine the effect of such COP data on joint kinetics during sprint running performances. COP data were collected from two piezoelectric force plates as a trolley wheel was rolled across the boundary between the plates. Position data for the trolley were collected using an opto-electronic motion analysis system for comparison with COP data. Mean COP errors during transition across the plate boundary were 0.003 +/- 0.002 m relative to a control point. Kinematic and kinetic data were also collected from eight athletes during sprint running trials to demonstrate the sensitivity of the inverse dynamics analysis to COP error for the ground contact phase of the dynamic movement trials. Kinetic sensitivity to the COP error was assessed during the entire stance phase for the ankle, knee, and hip joints and was less than 5% and 3% for joint moment and power data, respectively. Based on the small COP error during transition across plate boundaries, it is recommended that foot contacts overlapping two force plates may be included in inverse dynamics analyses.
- The reliability of accelerometry to measure weightlifting performance. [Comparative Study, Journal Article, Validation Studies]
- Sports Biomech 2012 Nov; 11(4):524-31.
The purposes of the study were to track weightlifters' barbell acceleration with a portable accelerometer over three training sessions to examine test-retest reliability and to compare peak barbell acceleration at different training intensities. Twelve nationally ranked weightlifters volunteered for this study. The portable accelerometer was attached to the right side of the barbell to measure barbell resultant acceleration during the snatch lift at a sampling frequency of 100 Hz. The data were collected over three training sessions at intensity levels of 80%, 85%, and 90% of one repetition maximum. The data were analyzed using intra-class correlation coefficients (ICCs) for the three training sessions and one-way repeated measure ANOVA to compare the difference in peak barbell acceleration at three intensities. Results showed that the device was highly reliable with an ICC of 0.88 and 95% confidence interval of 0.81-0.93. There were significant differences in peak barbell acceleration at various lifting intensities, indicating a decline of the acceleration as the mass of the barbell became heavier. The portable accelerometer seems useful in measuring barbell acceleration data, which can be analyzed in future studies to monitor a weightlifter's performance in a practical setting instead of testing at a laboratory.
- An observational model for biomechanical assessment of sprint kayaking technique. [Journal Article, Review]
- Sports Biomech 2012 Nov; 11(4):507-23.
Sprint kayaking stroke phase descriptions for biomechanical analysis of technique vary among kayaking literature, with inconsistencies not conducive for the advancement of biomechanics applied service or research. We aimed to provide a consistent basis for the categorisation and analysis of sprint kayak technique by proposing a clear observational model. Electronic databases were searched using key words kayak, sprint, technique, and biomechanics, with 20 sources reviewed. Nine phase-defining positions were identified within the kayak literature and were divided into three distinct types based on how positions were defined: water-contact-defined positions, paddle-shaft-defined positions, and body-defined positions. Videos of elite paddlers from multiple camera views were reviewed to determine the visibility of positions used to define phases. The water-contact-defined positions of catch, immersion, extraction, and release were visible from multiple camera views, therefore were suitable for practical use by coaches and researchers. Using these positions, phases and sub-phases were created for a new observational model. We recommend that kayaking data should be reported using single strokes and described using two phases: water and aerial. For more detailed analysis without disrupting the basic two-phase model, a four-sub-phase model consisting of entry, pull, exit, and aerial sub-phases should be used.
- The effects of load on system and lower-body joint kinetics during jump squats. [Journal Article]
- Sports Biomech 2012 Nov; 11(4):492-506.
To investigate the effects of different loads on system and lower-body kinetics during jump squats, 12 resistance-trained men performed jumps under different loading conditions: 0%, 12%, 27%, 42%, 56%, 71%, and 85% of 1-repetition maximum (1-RM). System power output was calculated as the product of the vertical component of the ground reaction force and the vertical velocity of the bar during its ascent. Joint power output was calculated during bar ascent for the hip, knee, and ankle joints, and was also summed across the joints. System power output and joint power at knee and ankle joints were maximized at 0% 1-RM (p < 0.001) and followed the linear trends (p < 0.001) caused by power output decreasing as the load increased. Power output at the hip was maximized at 42% 1-RM (p = 0.016) and followed a quadratic trend (p = 0.030). Summed joint power could be predicted from system power (p < 0.05), while system power could predict power at the knee and ankle joints under some of the loading conditions. Power at the hip could not be predicted from system power. System power during loaded jumps reflects the power at the knee and ankle, while power at the hip does not correspond to system power.
- Power production of the lower limbs in flutter-kick swimming. [Comparative Study, Journal Article]
- Sports Biomech 2012 Nov; 11(4):480-91.
This study aimed to compare the power produced by the flutter-kick action at different swimming velocities. Eighteen high-level male swimmers completed a maximal 15-m flutter-kicking sprint and underwent two tests (one passive and one with maximal flutter-kicking) in which they were towed at six velocities ranging from 1.0 to 2.0 m/s. Power values were computed for each velocity, and selected kinematic indices were evaluated at 1.2 and 2.0 m/s. The highest power (54 +/- 8 W) was observed at the velocity at which the drag equaled the propulsive force (1.27 +/- 0.08 m/s), which was similar to that recorded in the flutter-kicking sprint (1.26 +/- 0.09 m/s). Thereafter, power decreased significantly with increasing velocity, up to 17 +/- 10W (at 2.0 m/s). The angle between the horizontal and the line connecting the highest and lowest points of the malleolus trajectory was significantly wider at 1.2 m/s than at 2.0 m/s (75 +/- 4 degrees vs. 63 +/- 6 degrees). This could explain the change of power with velocity because all the other kinematic indices considered were similar at the two velocities. These results suggest that the propulsive role of the flutter-kick increases as the swimming velocity decreases.
- The effect of chalk on the finger-hold friction coefficient in rock climbing. [Comparative Study, Journal Article]
- Sports Biomech 2012 Nov; 11(4):473-9.
The main purpose of this study was to examine the effect of chalk on the friction coefficient between climber's fingers and two different rock types (sandstone and limestone). The secondary purpose was to investigate the effects of humidity and temperature on the friction coefficient and on the influence of chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed. Participants hung from holds which were fixed on a specially designed hang board. The inclination of the hang board was progressively increased until the climber's hand slipped from the holds. The angle of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient was calculated at the moment of slip. The results showed that there was a significant positive effect of chalk on the coefficient of friction (+18.7% on limestone and +21.6% on sandstone). Moreover sandstone had a higher coefficient of friction than limestone (+15.6% without chalk, +18.4% with chalk). These results confirmed climbers' belief that chalk enhances friction. However, no correlation with humidity/temperature and friction coefficient was noted which suggested that additional parameters should be considered in order to understand the effects of climate on finger friction in rock climbing.
- Step width alters iliotibial band strain during running. [Journal Article]
- Sports Biomech 2012 Nov; 11(4):464-72.
This study assessed the effect of step width during running on factors related to iliotibial band (ITB) syndrome. Three-dimensional (3D) kinematics and kinetics were recorded from 15 healthy recreational runners during overground running under various step width conditions (preferred and at least +/- 5% of their leg length). Strain and strain rate were estimated from a musculoskeletal model of the lower extremity. Greater ITB strain and strain rate were found in the narrower step width condition (p < 0.001, p = 0.040). ITB strain was significantly (p < 0.001) greater in the narrow condition than the preferred and wide conditions and it was greater in the preferred condition than the wide condition. ITB strain rate was significantly greater in the narrow condition than the wide condition (p = 0.020). Polynomial contrasts revealed a linear increase in both ITB strain and strain rate with decreasing step width. We conclude that relatively small decreases in step width can substantially increase ITB strain as well as strain rates. Increasing step width during running, especially in persons whose running style is characterized by a narrow step width, may be beneficial in the treatment and prevention of running-related ITB syndrome.
- Muscle activation characteristics in cross-country skiers with a history of anterior compartment pain. [Journal Article]
- Sports Biomech 2012 Nov; 11(4):452-63.
A large proportion of elite cross-country skiers suffer from chronic anterior compartment syndrome (CACS). This study used surface electromyograms (EMGs) to investigate whether differences existed in the activation characteristics of the tibialis anterior muscle between elite cross-country skiers with a history of anterior compartment pain (symptomatic group) and a pain-free control group. Based on self-reported pain symptoms, twelve young, national-level cross-country ski athletes were assigned to a symptomatic group (N = 5), a control group (N = 4), or analyzed individually if their diagnosis was not certain (N = 3). During skating, EMGs were recorded on five lower leg muscles. The relative increase in EMG power per step when increasing the effort level of skating was larger in the symptomatic group than in the control group for tibialis anterior (143 +/- 12% vs. 125 +/- 23%; Cohen's d = 1.17), peroneus longus (123 +/- 24% vs. 107 +/- 6%; d = 0.91), and gastrocnemius lateralis (167 +/- 51% vs. 117 +/- 12%; d = 1.64). The symptomatic group showed more power in the lower frequency bands of the tibialis anterior's EMG spectra (p < 0.001), whereas no group differences were found in other muscles (all p > 0.2). Within the step cycle, these differences appeared in the swing phase and in the gliding phase during single leg support. The observed differences in the EMG spectra may serve as an early identification of athletes who are at risk of developing CACS.
- Upper limb muscle fatigue during prolonged Boccia games with underarm throwing technique. [Journal Article, Research Support, Non-U.S. Gov't]
- Sports Biomech 2012 Nov; 11(4):441-51.
This study investigated the acute fatigue pattern in neuromuscular activity after a simulated Boccia game and the effect of fatigue pattern on sport performance. Nine elite Boccia athletes were tested before, during, and after a simulated game. Maximum ball speed was captured with video, and the target hitting rate and rating of perceived exertion (RPE) score were collected and analyzed. Electromyography signals from the upper trapezius, anterior deltoid, posterior deltoid, biceps brachii, triceps brachii, and wrist extensor muscles were collected by surface electrode and were evaluated with mean power frequency (MPF). Only the upper trapezius muscle showed fatigue as demonstrated by a reduction of MPF of 8% (p = 0.027) when comparing the first and last throws in a simulated game. Subjective RPE score increased during the game (118%, p = 0.004), and sports performance in terms of maximum ball speed (-12%, p = 0.004) and target hitting rate (-25%, p = 0.004) also deteriorated. In conclusion, fatigue on the upper trapezius muscle was demonstrated in elite Boccia athletes following a prolonged Boccia game and may have affected Boccia performance. Preventative measures against upper trapezius muscle fatigue and endurance training for synergists of the upper trapezius muscle may be considered in future studies.