Which drop jump technique is most effective at enhancing countermovement jump ability, “countermovement” drop jump or “bounce” drop jump?

Abstract

The drop jump is a popular form of plyometric exercise often undertaken to enhance countermovement jump ability (jump height). Despite its popularity the effects of drop jump training on countermovement jump height are often inconsistent. Such inconsistencies may be as a result of differences in the drop jump technique being employed. Two recognised forms of drop jump are the “countermovement” drop jump and the “bounce” drop jump and the current study examined the effects of eight weeks of training with these drop jump techniques on countermovement jump height. Methods: A kinetic and kinematic analysis of each participant's countermovement jump, bounce- and countermovement drop jumps was undertaken prior to training. Participants were then randomly assigned to a bounce drop jump training group (n = 34), a countermovement drop jump training group (n = 35) or a control group (n = 34). Changes in jump height were examined following training. Results: The countermovement drop jump training group increased their countermovement jump height by 2.9 cm (6%), which was a significant change (P < 0.05) in comparison to that experienced by the bounce drop jump (-0.2 cm, -0.4%) and the control group (-0.1 cm, 0.2%). Conclusion: The countermovement drop jump may be more effective than the bounce drop jump at enhancing countermovement jump height.     

Alterations in Body Size and Composition Consequent to Astro-Trimmer and Slim-Skins Training Programs

Tennis is an activity requiring both endurance and anaerobic components, which could have immunosuppressive effects postexercise.

Purpose

The purpose of this investigation was to determine the effect of a simulated tennis match on apoptotic and migratory markers on lymphocyte subsets.

Method

Male high school (n = 5) and college (n = 3) tennis players (M _age = 18.9 ± 3.3 years) completed 10 sets of a tennis protocol including serves, forehand strokes, and backhand groundstrokes with 1-min rest periods between sets. Apoptosis antigen 1 receptor (CD95) and chemokine receptor fractalkine (CX₃CR1) expression was analyzed on helper T lymphocytes (CD4+), cytotoxic T lymphocytes (CD8+), and B lymphocytes (CD19+) twice, at resting baseline and immediately after all 10 sets of the tennis protocol.

Results

An increase was observed in each lymphocyte subtype (p < .02, effect size = .41), and comparison of absolute changes revealed increases in CD4+/CD95+, CD8+/CD95+, and CD8+/CX₃CR1 lymphocytes following the tennis protocol (p < .01, effect size = .43), but not in CD19+ cells.

Conclusions

A simulated tennis match has adequate intensity to induce immune modulations in terms of increased cell death and cellular migration in T lymphocyte subsets. Lymphocytopenia following tennis play is influenced by both apoptotic and migratory mechanisms.     

Gait Transitions of Persons With and Without Intellectual Disability

This study examined whether the walk-to-run transition speed (W-RTS) and the run-to-walk transition speed (R-WTS) were different or more variable between participants with and without intellectual disability (ID). Nine adults with ID and 10 adults without ID completed in a series of walk-to-run and run-to-walk trials on a treadmill. W-RTS and R-WTS were identified using force-sensitive resistors. When transition speeds were expressed as Froude numbers to account for differences in leg length, W-RTS was slower, and intraindividual variability of W-RTS and R-WTS was greater in participants with ID. These findings support the idea that the unique constraints of individuals with ID result in altered attractor dynamics for walking and a weaker coupling between locomotor speed and order parameters governing gait transitions.     

Estimated maturity status and perceptions of adult autonomy support in youth soccer players

Abstract

In this study, we examined the relations between biological maturity status, body mass index, age, and perceptions of adult autonomy support in the context of youth soccer. A total of 70 female and 43 male soccer players, aged 9 – 15 years, completed three adult-specific versions (i.e. mother, father, coach) of the perceived autonomy support subscale from the Interpersonal Style Scale. The participants' percent predicted adult stature was used as an estimate of biological maturity status. Multiple linear regression analyses revealed that advanced maturity status in male players predicted lower perceptions of autonomy support from the coach. Maturity status was unrelated to perceptions of autonomy support from the coach in female soccer players, and paternal and maternal autonomy support in male and female players. Age and body mass index were unrelated to perceptions of adult (i.e. coach, mother, father) autonomy support in male and female players.     

Hip adductor activations during run-to-cut manoeuvres in compression shorts: implications for return to sport after groin injury

Abstract

Athletes at high risk of groin strains in sports such as hockey and soccer often choose to wear shorts with directional compression to aid in prevention of or recovery from hip adductor strains. Large, eccentric contractions are known to result in or exacerbate strain injuries, but it is unknown if these shorts have a beneficial effect on hip adductor muscle activity. In this study, surface electromyography (EMG) of the adductor longus and ground reaction force (GRF) data were obtained simultaneously on 29 healthy individuals without previous history of serious injury while performing unanticipated 45° run-to-cut manoeuvres in a laboratory setting wearing shorts with non-directional compression (control, HeatGear, Under Armour, USA) or shorts with directional compression (directional, CoreShort PRO, Under Armour, USA), in random order. Average adductor activity in the stance leg was significantly lower in the directional condition than in the control condition during all parts of stance phase (all P < 0.042). From this preliminary analysis, wearing directional compression shorts appears to be associated with reduced stance limb hip adductor activity. Athletes seeking to reduce demand on the hip adductors as they approach full return to activities may benefit from the use of directional compression shorts.     

Tackle and impact detection in elite Australian football using wearable microsensor technology

Abstract

The effectiveness of a wearable microsensor device (MinimaxX^TM S4, Catapult Innovations, Melbourne, VIC, Australia) to automatically detect tackles and impact events in elite Australian football (AF) was assessed during four matches. Video observation was used as the criterion measure. A total of 352 tackles were observed, with 78% correctly detected as tackles by the manufacturer’s software. Tackles against (i.e. tackled by an opponent) were more accurately detected than tackles made (90% v 66%). Of the 77 tackles that were not detected at all, the majority (74%) were categorised as low-intensity. In contrast, a total of 1510 “tackle” events were detected, with only 18% of these verified as tackles. A further 57% were from contested ball situations involving player contact. The remaining 25% were in general play where no contact was evident; these were significantly lower in peak Player Load? than those involving player contact (P < 0.01). The tackle detection algorithm, developed primarily for rugby, was not suitable for tackle detection in AF. The underlying sensor data may have the potential to detect a range of events within contact sports such as AF, yet to do so is a complex task and requires sophisticated sport and event-specific algorithms.     

Information recall of younger and older skilled athletes: The role of display complexity,attentional resources and visual exposure duration

This study was concerned with the interactive role of experience of athletic skill with other relevant environmental variables (display complexity, attentional resources, exposure time of stimuli) on perception (recall) of structured handball game situations. Nineteen experienced (older) and 19 less experienced (younger) handball players were assigned randomly either to ball‐bouncing (diverted attention) or to calm seated (focused attention) conditions. In each of the two conditions, the subjects were exposed to a total of 36 slides containing 2–3, 5–6 and 8–10 players. Eighteen slides were exposed for 0.5 s and 18 for 1.0 s. All the slides contained structured defence and offence situations. Recall scores were subjected to repeated‐measures ANOVA using attention condition and age as between‐subject factors and task complexity and exposure duration as within‐subject factors. The results showed that the recall of less experienced players deteriorated more than the recall of more experienced players following exposure to complex displays (≥ 8 players) while engaging in a secondary task (bouncing). The findings suggest that research paradigms should be applied in the field of sport which share both ecological validity and a potential to discover the cognitive substrates underlying experience and age in skilled motor performance.     

The Effects of Three Styles of Teaching on the Psychomotor Performance And Social Skill Development of Fifth Grade Children

Abstract

The effects of Mosston's teaching styles B, C and E were examined in terms of motor skill acquisition and social skill development of fifth grade children. Ninety-six children, randomly selected and randomly assigned to one of three treatment groups, were taught a hockey accuracy task. Motor performance data were collected prior to, midway through, and following training; they were analyzed within groups, to determine if learning was evident, and across groups, to examine the relative effectiveness of these three styles of teaching. Social behavior patterns observed during learner-to-learner interaction were also examined during a second task in which pairs of learners were asked to “help” each other learn the task. A 3 × 3 analysis of variance with repeated measures revealed that (1) all three groups learned the task and (2) they learned comparably well. It was concluded that these three styles of teaching are all effective in facilitating learning of this type of motor task. Style C, an arrangement in whcih learners work in pairs, one performing the task while being provided with formative feedback by the other, was found not only to produce comparable learning, but to significantly enhance social skill development on those behaviors associated with giving feedback and receiving it from a peer.     

Response to a Cold Pressor Test during Physical Training

Abstract

Members of the 1958–59 varsity basketball team at Santa Barbara and a control group of physical education majors not in training were tested each three weeks during a 17-week season of basketball competition on their response to a step test and to a cold pressor test. The results indicated that significant step test recovery pulse rate changes were made by the basketball players after three weeks of training. Maximum changes were found to occur after 17 weeks of training. The diastolic pressure response to the cold pressor test increased significantly (7 mmHg.) after six weeks of training and this was maintained for 17 weeks. The results indicated that a possible increased sensitivity or tone of the peripheral vessels resulted from physical training.     

Wikipedia,Critical Social Theory,and the Possibility of Rational Discourse 1

Information systems researchers that apply critical social perspectives frequently emphasize the potential for information technology to serve as a mechanism for increased rationalization, domination, and control. Such theorists often overlook or discount the liberating aspects of information systems. In this study, we apply the ideal of rational discourse developed by Jürgen Habermas to the phenomenon of Wikipedia in an effort to explore empirically the emancipatory potential of information systems. We contend that Wikipedia embodies an approximation of the necessary conditions for rational discourse. While several challenges persist, the example of Wikipedia illustrates the positive potential of information systems in supporting the emergence of more emancipatory forms of communication. The corresponding implications for researchers and design professionals alike are discussed.