Lunge performance and its determinants

For activities such as squash, badminton and fencing, the ability to quickly complete a lunge and return to the start or move off in another direction is critical for success. Determining which strength qualities are important predictors of lunge performance was the focus of this study. Thirty-one male athletes performed: (1) a unilateral maximal squat (one-repetition maximum, 1-RM) and unilateral jump squat (50% 1-RM) on an instrumented supine squat machine, and (2) a forward lunge while attached to a linear transducer. We performed stepwise multiple regression analysis with lunge performance as the dependent variable and various strength, flexibility and anthropometric measures as the independent variables. From the many strength and power measures calculated, time to peak force was the best single predictor of lunge performance, which accounted for 55% of the explained variance. The best three-variable model for predicting lunge performance accounted for 76-85% of the explained variance. The models differed, however, according to whether lunge performance was expressed relative to body mass (time to peak force, mean power and relative strength = 76%) or taken as an absolute value (time to peak force, leg length and flexibility = 85%). We conclude that one to two trials were reliable for strength diagnosis and that one strength measure cannot accurately explain functional performance because other factors, such as body mass, flexibility and leg length, have diverse effects on the statistical models.     

Impact forces and neck muscle activity in heading by collegiate female soccer players

Three soccer header types (shooting, clearing and passing) and two heading approaches (standing and jumping) were manipulated to quantify impact forces and neck muscle activity in elite female soccer players. The 15 participants were Division I intercollegiate soccer players. Impact forces were measured by a 15-sensor pressure array secured on the forehead. The electromyographic (EMG) activity of the left and right sternocleidomastoid and trapezius muscles was recorded using surface electrodes. Maximum impact forces and impulses as well as the EMG data were analysed with separate repeated-measures analyses of variance. Impact forces and impulses did not differ among the header types or approaches. Higher values were found for jumping versus standing headers in the mean normalized EMG for the right sternocleidomastoid. In addition, the integrated EMG was greater for the right sternocleidomastoid and right and left trapezius (P < 0.05). The sternocleidomastoid became active earlier than the trapezius and showed greater activity before ball contact. The trapezius became active just before ball contact and showed greater activity after ball contact. The increased muscle activity observed in the neck during the jumping approach appears to stabilize the connection between the head and body, thereby increasing the stability of the head-neck complex.     

Some thoughts about resilience versus positive development, main effects versus interactions, and the value of resilience

Interaction effects are the defining feature of resilience and resilience research and are responsible for the unique contributions of this field of study to our understanding of human development. The methodological and statistical challenges posed by interaction effects do not, by themselves, undermine the value of resilience as a construct.     

The Loughborough Intermittent Shuttle Test: a field test that simulates the activity pattern of soccer

The aims of this study were to describe and determine the test-retest reliability of an exercise protocol, the Loughborough Intermittent Shuttle Test (the LIST), which was designed to simulate the activity pattern characteristic of the game of soccer. The protocol consisted of two parts: Part A comprised a fixed period of variable-intensity shuttle running over 20 m; Part B consisted of continuous running, alternating every 20 m between 55% and 95% VO2max, until volitional fatigue. Seven trained games players (age 21.5+/-0.9 years, height 182+/-2 cm, body mass 80.1+/-3.6 kg, VO2max 59.0+/-1.9 ml x kg(-1) x min(-1); mean +/- s(x)) performed the test on two occasions (Trial 1 and Trial 2), at least 7 days apart, to determine the test-retest reliability of the sprint times and running capacity. The physiological and metabolic responses on both occasions were also monitored. The participants ingested water ad libitum during the first trial, and were then prescribed the same amount of water during the second trial. The 15 m sprint times during Trials 1 and 2 averaged 2.42+/-0.04 s and 2.43+/-0.04 s, respectively. Run time during Part B was 6.3+/-2.0 min for Trial 1 and 6.1+/-1.3 min for Trial 2. The 95% limits of agreement for sprint times and run times during Part B were -0.14 to 0.12 s and -3.19 to 2.16 min respectively. There were no differences between trials for heart rate, rating of perceived exertion, body mass change during exercise, or blood lactate and glucose concentrations during the test. Thus, we conclude that the sprint times and the Part B run times were reproducible within the limits previously stated. In addition, the activity pattern and the physiological and metabolic responses closely simulated the match demands of soccer.     

Learning and remembering strategies of novice and advanced jazz dancers for skill level appropriate dance routines

This study examined the influence of the challenge level of to-be-learned stimulus on learning strategies in novice and advanced dancers. In Study 1, skill-level appropriate dance routines were developed for novice and advanced jazz dancers. In Study 2, 8 novice and 9 advanced female jazz dancers attempted to learn and remember the two routines in mixed model factorial design, with one between-participants factor: skill level (novice or advanced) and two within-participants factors: routine (easy or difficult) and performance (immediate or delayed). Participants were interviewed regarding the strategies used to learn and remember the routines. Results indicated that advanced performers used atypical learning strategies for insufficiently challenging stimuli, which may reflect characteristics of the stimuli rather than the performer. The qualitative data indicate a clear preference of novice and advanced performers for spatial compatibility of stimuli and response.     

Leisure time physical activity in Australian women: relationship with well being and symptoms

This paper explores the association between moderate levels of physical activity (PA) and health benefits in well being and symptoms such as tiredness, back pain, and constipation. Participants in the Australian Longitudinal Study on Women's Health, 14,502 young women (ages 18-23 years), 13,609 middle-age women (45-50 years), and 11,421 older women (ages 70-75 years), answered questions about vigorous and less vigorous exercise (used to determine a physical activity score), well being (SF-36), symptoms, and medical conditions. There were significant associations between the PA score and SF-36 in each cohort. Odds ratios (OR) for a range of symptoms and conditions were lower for women who reported low to moderate activity than for sedentary women, for example, for young women or for constipation = 0.76 (CI, 0.65-0.89), for middle-age women or for tiredness = 0.70 (0.63-0.78). There was no threshold of PA at which health benefits increased significantly. Although cross-sectional, the findings suggest that low-to-moderate levels of exercise are associated with a range of health benefits for women of all ages. These preliminary findings will be followed up during the longitudinal study.