Eric L. Sauers
Jorge E. Morais, António J. Silva, Daniel A. Marinho, Ludovic Seifert and Tiago M. Barbosa
To apply a new method to identify, classify, and follow up young swimmers based on their performance and its determinant factors over a season and analyze the swimmers’ stability over a competitive season with that method.
Fifteen boys and 18 girls (11.8 ± 0.7 y) part of a national talent-identification scheme were evaluated at 3 different moments of a competitive season. Performance (ie, official 100-m freestyle race time), arm span, chest perimeter, stroke length, swimming velocity, speed fluctuation, coefficient of active drag, propelling efficiency, and stroke index were selected as variables. Hierarchical and k-means cluster analysis were computed.
Data suggested a 3-cluster solution, splitting the swimmers according to their performance in all 3 moments. Cluster 1 was related to better performances (talented swimmers), cluster 2 to poor performances (nonproficient swimmers), and cluster 3 to average performance (proficient swimmers) in all moments. Stepwise discriminant analysis revealed that 100%, 94%, and 85% of original groups were correctly classified for the 1st, 2nd, and 3rd evaluation moments, respectively (0.11 ≤ Λ ≤ 0.80; 5.64 ≤ χ2 ≤ 63.40; 0.001 < P ≤ .68). Membership of clusters was moderately stable over the season (stability range 46.1–75% for the 2 clusters with most subjects).
Cluster stability is a feasible, comprehensive, and informative method to gain insight into changes in performance and its determinant factors in young swimmers. Talented swimmers were characterized by anthropometrics and kinematic features.
Susan Vincent Graser, Robert P. Pangrazi and William J. Vincent
The purpose was to determine if waist placement of the pedometer effected accuracy in normal, overweight, and obese children, when attaching the pedometer to the waistband or a belt.
Seventy-seven children (ages 10-12 y) wore five pedometers on the waistband of their pants and a belt at the following placements: navel (NV), anterior midline of the right thigh (AMT), right side (RS), posterior midline of the right thigh (PMT), and middle of the back (MB). Participants walked 100 steps on a treadmill at 80 m · min−1.
The RS, PMT, and MB sites on the waistband and the AMT and RS sites on the belt produced the least error.
Of these sites the RS placement is recommended because of the ease of reading the pedometer during activity. Using a belt did not significantly improve accuracy except for normal weight groups at the NV placement site.
Lee Nolan, Benjamin L. Patritti, Laura Stana and Sean M. Tweedy
The purpose of this study was to evaluate the extent to which residual shank length affects long jump performance of elite athletes with a unilateral transtibial amputation. Sixteen elite, male, long jumpers with a transtibial amputation were videoed while competing in major championships (World Championships 1998, 2002 and Paralympic Games, 2004). The approach, take-off, and landing of each athlete’s best jump was digitized to determine residual and intact shank lengths, jump distance, and horizontal and vertical velocity of center of mass at touchdown. Residual shank length ranged from 15 cm to 38 cm. There were weak, nonsignificant relationships between residual shank length and (a) distance jumped (r = 0.30), (b) horizontal velocity (r = 0.31), and vertical velocity (r = 0.05). Based on these results, residual shank length is not an important determinant of long jump performance, and it is therefore appropriate that all long jumpers with transtibial amputation compete in the same class. The relationship between residual shank length and key performance variables was stronger among athletes that jumped off their prosthetic leg (N = 5), and although this result must be interpreted cautiously, it indicates the need for further research.
Tara Jo Manal and Roschella Claytor
Jennifer S. Howard and Dustin Briggs
Column-editor : Carl G. Mattacola
John L. Walker, Tinker D. Murray, James Eldridge, William G. Squires, Jr., Pete Silvius and Erik Silvius
Paul D. Loprinzi and Ovuokerie Addoh
This study evaluated a physical activity–related obesity model on mortality.
Data from the 1999–2006 NHANES were used (N = 16,077), with follow-up through 2011. Physical activity (PA) was subjectively assessed, with body mass index (BMI) and waist circumference (WC) objectively measured. From these, 12 mutually exclusive groups (G) were evaluated, including: G1: Normal BMI, Normal WC and Active; G2: Normal BMI, Normal WC and Inactive; G3: Normal BMI, High WC and Active; G4: Normal BMI, High WC and Inactive; G5: Overweight BMI, Normal WC and Active; G6: Overweight BMI, Normal WC and Inactive; G7: Overweight BMI, High WC and Active; G8: Overweight BMI, High WC and Inactive; G9: Obese BMI, Normal WC and Active; G10: Obese BMI, Normal WC and Inactive; G11: Obese BMI, High WC and Active; and G12: Obese BMI, High WC and Inactive.
Compared with G2, the following had a reduced mortality risk: G1, G3, G5, G6, G7, G8, G9, and G11. Compared with G12, the following had a reduced mortality risk: G1, G3, G5, G7, G9, and G11. In each respective group for BMI and WC, the active group had a reduced mortality risk.
Across all BMI and WC combinations, PA improved mortality risk identification.
Cloe Cummins, Blake McLean, Mark Halaki and Rhonda Orr
To quantify the external training loads of positional groups in preseason training drills.
Thirty-three elite rugby league players were categorized into 1 of 4 positional groups: outside backs (n = 9), adjustables (n = 9), wide-running forwards (n = 9), and hit-up forwards (n = 6). Data for 8 preseason weeks were collected using microtechnology devices. Training drills were classified based on drill focus: speed and agility, conditioning, and generic and positional skills.
Total, high-speed, and very-high-speed distance decreased across the preseason in speed and agility (moderate, small, and small, respectively), conditioning (large, large, and small) and generic skills (large, large, and large). The duration of speed and generic skills also decreased (77% and 48%, respectively). This was matched by a concomitant increase in total distance (small), high-speed running (small), very-high-speed running (moderate), and 2-dimensional (2D) BodyLoad (small) demands in positional skills. In positional skills, hit-up forwards (1240 ± 386 m) completed less very-high-speed running than outside backs (2570 ± 1331 m) and adjustables (2121 ± 1163 m). Hit-up forwards (674 ± 253 AU) experienced greater 2D BodyLoad demands than outside backs (432 ± 230 AU, P = .034). In positional drills, hit-up forwards experienced greater relative 2D BodyLoad demands than outside backs (P = .015). Conversely, outside backs experienced greater relative high- (P = .007) and very-high-speed-running (P < .001) demands than hit-up forwards.
Significant differences were observed in training loads between positional groups during positional skills but not in speed and agility, conditioning, and generic skills. This work also highlights the importance of different external-load parameters to adequately quantify workload across different positional groups.