The purpose of this paper is to demonstrate the importance of using developmentally appropriate serving strategies that will promote the game of volleyball and facilitate learning while minimizing injury. A critical review of serving discusses the main developmental, maturational, and technical issues related to socialization and long-term development in volleyball. Teaching complex serving styles (such as the jump serve to athletes under the age of 14) might have implications for athletes’ long-term development and might lead to injury. The adoption of developmentally appropriate practices in coaching young athletes is still a novelty for many coaches. Therefore, this article stresses the importance of implementing adapted or modified games and of teaching skills in a progressive fashion to aid development.

(2008). Applying Newton's Apple to Elementary Physical Education. Journal of Physical Education, Recreation & Dance: Vol. 79, No. 8, pp. 43-51.

The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79 degrees +/- 11.78 degrees ) resulted in significantly (p = .001) less hip flexion than did the self-preferred (41.25 degrees +/- 12.89 degrees ) and rear foot (43.15 degrees +/- 11.77 degrees ) techniques. At peak vertical ground reaction force, the rear foot technique (26.77 degrees +/- 9.49 degrees ) presented significantly lower (p = .001) knee flexion angles as compared with forefoot (58.77 degrees +/- 20.00 degrees ) and self-preferred (54.21 degrees +/- 23.78 degrees ) techniques. A significant difference for knee valgus angles (p = .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12 degrees +/- 7.51 degrees ) and forefoot (4.97 degrees +/- 7.90 degrees ) techniques presented greater knee varus angles as compared with the rear foot technique (0.08 degrees +/- 6.52 degrees ). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.

The between-trial repeatability of movement patterns when assessing potentially at-risk motion characteristics during jump-landing tasks is critical to identifying biomechanical risk factors for anterior cruciate ligament (ACL) injury. PURPOSE: The purpose of this study was to analyze kinematic variables' inter-trial reliability within one session of performing a jump-landing task from a box. The study aimed to evaluate inter-trial reliability on four kinematic variables at initial ground contact (IGC); hip flexion, knee flexion, knee valgus, and ankle flexion (all measured in angular degrees) and across gender. METHODS: Twenty-five males (24±2.3yrs, 178.6±7.2cm, and 84.1±13.1kg) and twenty-five females (23±2.5yrs, 167.2±7.4cm, and 62.8±8.5kg) were selected from a sample of convenience from a university student population. 3-D electromagnetic motion analysis sensors sampling at 100Hz and two Bertec force plates sampling at 1000 Hz, used to assess initial ground contact, were utilized for data collection. Five trials were conducted and each trial was considered as a separate data point and evaluated using an intraclass correlation coefficient model (ICC 2,k) to analyze the reliability of each variable at IGC. RESULTS: All variables were significant at p<0.05. Fair to excellent reliability (ICC=0.79 to 0.92) was demonstrated for each variable across the total sample. Males tended to be very slightly more reliable across trials as compared to their female counterparts; Hip Flexion at IGC (Males=0.89 vs. Females=0.83), Knee Flexion at IGC (Males=0.81 vs. Females 0.77), Knee Valgus at IGC (Males=0.93 vs. Females=0.92), and Ankle Flexion at IGC (Males=0.85 vs. Females=0.78). CONCLUSION: Repeatability of lower extremity kinematic data across five trials during a single-session jump landing task showed fair to excellent reliability within and between gender. Evaluation of kinematic movement characteristics during a controlled box-drop jump-landing task revealed reliable individual movement patterns between trials allowing researchers to better utilize a single-session analysis for identification of potential ACL injury risk factors. Future studies should focus on evaluating the inter-trial variability of kinematic data across multiple sessions and various jump-landing movement tasks.

Oftentimes while conducting biomechanical analyses in attempts to understand injury (e.g., ACL and ankle) risk factors mean scores of several trials are utilized to evaluate individual movement patterns; yet, analysis of inter-trial variability within a single session merits further consideration. PURPOSE: The purpose of this study was to analyze inter-trial reliability within one session of performing a jump-landing task from a box. The study aimed to evaluate inter-trial reliability on the kinetic variables (vertical ground reaction force and proximal tibial anterior shear force) at three instants (maximum vertical ground reaction force (MVGRF), maximum knee flexion (MKF), and maximum proximal tibial anterior shear force (MPTASF) in a jump-landing task across gender. METHODS: Twenty-five males (24±2.3yrs, 178.6±7.2cm, and 84.1±13.1kg) and twenty-five females (23±2.5yrs, 167.2±7.4cm, and 62.8±8.5kg) were selected from a sample of convenience from a university student population. 3-D electromagnetic motion analysis sensors sampling at 1 00Hz and two Bertec force plates sampling at 1000 Hz were used for data collection. Five trials were conducted and each trial was considered as a separate data point and evaluated using an intraclass correlation coefficient model (ICC 2,k) to analyze the reliability of each variable at different time instants. RESULTS: All variables were significant different at p<0.05. Moderate to poor reliability was shown for vertical ground reaction force (0.67) and proximal tibial anterior shear force (0.32) at MVGRF across gender with minimal differences between males (0.62, 0.24) and females (0.73, 0.44), respectively. The maximum kinetic values also revealed poor reliability (MVGRF 0.35 and MPTASF 0.38) across gender with minimal differences between genders (females=0.28, vs. males=0.42). Fair reliability was found for vertical ground reaction force at MKF (0.71), with females showing better reliability (0.84) as compared to their male counterparts (0.63). CONCLUSION: Five trials during a single-session jump landing task showed poor to fair reliability within ground reaction force and proximal tibial anterior shear force across gender. Future studies should focus on evaluating the inter-trial variability of kinetic data across multiple sessions.

Impact absorption during jump-landing tasks allows the body to disperse energy to allow for safe movement patterns. PURPOSE: The purpose of this study was to analyze kinetic patterns during the stop-jump landing phase when jumping from a box of 30cm during different foot position aspects (self-preferred, forefoot, and rearfoot). The study aimed to evaluate kinetic (vertical ground reaction force and proximal anterior tibial shear forces) at initial contact and maximum points, respectively, between the different foot-landing techniques and gender. METHODS: Twenty-five males (24.4±2.3yrs, 178.58±7.15cm, 84.09±13.14kg) and twenty-five females (23.2±2.5yrs, 167.22±7.38cm, 62.82±8.48kg) were selected from a sample of convenience from a university student population. Two Bertec 4060 series forceplates set at a sampling rate of 1000Hz and a 3-D electromagnetic motion analysis system set at a sampling rate of 1 00Hz were used for data collection. The rearfoot technique consisted of initial contact with the heel followed by the forefoot, while the opposite occurred for forefoot landing technique. Five trials were averaged for each technique and exported into SPSS version 12.0 for analysis. For each technique and at each of the time instants, the mean of five trials was analyzed using separate multivariate repeated measures analyses of variance (MANOVA) in SPSS version 12.0 with gender as the between factor and technique as the within factor using an alpha level of p< .05. RESULTS: Significant differences between foot-landing techniques were found for maximum vertical ground reaction force (p=.001) normalized to multiple of bodyweight (Mbw). The rearfoot technique resulted in significantly greater maximum vertical ground reaction force (4.98 ± 0.72 Mbw, p=.001) as compared the self-preferred (3.31 ± 0.75 Mbw) and forefoot landing techniques (3.09 ± 0.62Mbw). There were no significant differences found for maximum proximal anterior tibial shear force across the three landing techniques (p=.569). The rearfoot technique (0.22 ± 0.11 Mbw) showed a trend to be slightly greater than the forefoot technique (0.15±.06Mbw), yet no significant difference was found for maximum proximal anterior tibial shear force. No significant effects for gender were found for either variable. CONCLUSION: The rearfoot landing technique created the greatest maximum vertical ground reaction force across all three foot-landing styles, indicating greater impact absorption demands when first contacting with the rearfoot. Future studies should evaluate foot landing style effects on kinematic and kinetic variables during functional tasks.

Jump-landing tasks require the body to utilize various movement patterns in order to absorb the body's energy when landing. PURPOSE: The purpose of this study was to analyze lower extremity motion patterns during the stop-jump landing phase from a box of 30cm during different foot position aspects (self-preferred, forefoot, and rear foot). The study aimed to evaluate kinematic (knee flexion, knee valgus, ankle plantar-flexion, and hip flexion) differences at four instants (initial contact, maximum vertical ground reaction force, maximum knee flexion, and maximum proximal anterior tibial shear force) between the different foot-landing techniques and gender. METHODS: Twenty-five males (24.4±2.3yrs, 178.58±7.15cm, 84.09±13.14kg) and twenty-five females (23.2±2.5yrs, 167.22±7.38cm, 62.82±8.48kg) were selected from a sample of convenience from a University student population. A 3-D electromagnetic motion analysis system set at a sampling rate of 1 00Hz was used for data collection. The rearfoot technique consisted of initial contact with the heel followed by the forefoot, while the opposite occurred for forefoot landing technique. Five trials were averaged for each technique and exported into SPSS version 12.0 for analysis. Separate multivariate repeated measures analyses of variance (MANOVAs), with an alpha level set at p < .05, were used to analyze each variable at the different time instants with gender as the between factor and technique as the within factor. RESULTS: There were no significant differences found between genders at the four instants for each variable. There were significant differences found at initial contact in hip flexion angles between landing techniques (p = .001), the forefoot technique (35.79 ±11.78) resulted in less hip flexion than the self-preferred (41.25 ±12.89) and rear-foot (43.15 ±11.77) techniques. A significant difference was found between landing techniques at maximum vertical ground reaction force for knee flexion (p = .001). The rearfoot technique (26.77±9.49) presented lower knee flexion angles as compared to forefoot (58.77±20.00) and self-preferred (54.21±23.78) techniques. A significant difference of knee valgus angles was found between landing techniques at maximum vertical ground reaction force (p = .001). The self-preferred (4.12 ±7.51) and forefoot (4.97±7.90) techniques presented greater knee varus angles as compared to the rearfoot technique (0.08±6.52). CoNCLUsIoN: The rearfoot landing technique presented significant differences in the kinematic parameters when landing. Future studies should evaluate foot landing style effects on kinematic and kinetic variables during functional tasks.

Training mentors for new teachers will increase the quality of the mentors and will encourage veteran teachers to undertake the task of mentoring their colleagues.

Understanding how a variety of constraints influence movement will allow movement educators to plan lessons that have a greater chance for success.