Carry-over of force production symmetry in athletes of differing strength levels. J Strength Cond Res 29(11): 3188–3196, 2015—This study sought to determine the level of association between bilateral force production symmetry assessment methods (standing weight distribution [WtD], unloaded and lightly loaded jumps, and isometric strength) and to determine whether the amount of symmetry carry-over between these tasks differs for strong and weak athletes. Subjects for this study included male (n = 31) and female (n = 32) athletes from National Collegiate Athletic Association Division I sports. Athletes performed WtD, unloaded and lightly loaded (20 kg) static and countermovement jumps, and isometric midthigh pull (IMTP) assessments on 2 adjacent force plates. Ground reaction force data were used to calculate symmetry variables and performance-related variables. Using Pearson zero order correlations, evaluations of the amount of symmetry carry-over were made. Weight distribution correlated strongly with jump peak force (PF) (r = 0.628–0.664). Strong relationships were also observed between loading conditions for jump variables (r = 0.568–0.957) as were the relationships between jump types for PF, peak power, and net impulse (r = 0.506–0.834). Based on the pooled sample, there was a lack of association between IMTP and WtD for jump symmetry variables. However, when examining strong and weak groups, rate of force development showed moderate to strong symmetry carry-over in the strongest athletes (r = 0.416–0.589). Stronger athletes appear to display similar explosive strength symmetry characteristics in dynamic and isometric assessments, unlike weaker athletes. Strength seems to influence the amount of force production symmetry carry-over between bilateral assessments. There may be optimal loads and variables for symmetry assessment, but these may differ based on population characteristics.

The purpose of this investigation was to determine the existence of bilateral strength and force-production asymmetry and evaluate possible differences based on sex, as well as strength level. Asymmetry was assessed during weight-distribution (WtD) testing, unloaded and lightly loaded static- (SJ) and countermovement-jump (CMJ) testing, and isometric midthigh-pull (IMTP) strength testing. Subjects included 63 athletes (31 male, 32 female) for WtD, SJ, and CMJ tests, while 129 athletes (64 male, 65 female) participated in IMTP testing. Independent-samples t tests were used to determine possible differences in asymmetry magnitude between males and females, as well as between strong and weak athletes. Cohen d effect-size (ES) estimates were also used to estimate difference magnitudes. Statistically different asymmetry levels with moderate to strong ESs were seen between males and females in WtD, 0-kg SJ (peak force [PF]), 20-kg SJ (peak power [PP]), 0-kg CMJ (PF, PP, net impulse), and 20-kg CMJ (PF), but no statistical differences were observed in IMTP variables. Dividing the sample into strong and weak groups produced statistically significant differences with strong ES estimates in IMTP PF and rate of force development, and many ESs in jump symmetry variables increased. The results of this investigation indicate that females may be more prone to producing forces asymmetrically than males during WtD and jumping tasks. Similarly, weaker athletes displayed more asymmetry than stronger athletes. This may indicate that absolute strength may play a larger role in influencing asymmetry magnitude than sex.

Syfte: Syftet för studien var att undersöka om isometric mid-thigh pull (IMTP) tillsammans med (CMJ) kan anses som lämpliga testmetoder för att mäta prestation i hoppförmåga inom parkour/freerunning (PK/FR). Vi undersökte detta genom att mäta traceurers maximala styrka och explosiva styrka i de nedre extremiteterna, för att sedan jämföra resultaten med fysiskt aktiva idrottsstudenter på högskolenivå. Vi undersökte även om IMTP och CMJ korrelerar med varandra. Urval: 23 personer, 11 traceurer och 12 fysiskt aktiva idrottare rekryterades för denna studie. Metod: vi mätte maximal styrka: Peak force (PF) IMTP (N) på kraftplatta och maximal vertikal hopphöjd: CMJ (cm) på IR-matta. Statistisk analys: Shapiro Wilks användes för normalfördelningar, en oberoende tvåvägs Mann-Whitney U t-test användes för att undersöka skillnader mellan grupperna. Två Spearmans- och ett Pearsons korrelationskoefficienttest användes för att undersöka samband mellan IMTP och CMJ. Resultat: PK gruppen var normalfördelad i alla variabler IMTP (N) och CMJ (cm) men kontroll (KTRL) gruppen var ej normalfördelad i CMJ (cm) och gav utslag för IMTP (N). PK gruppen uppnådde ett IMTP (N) medianvärde på: 2269,9 ± 661.72N och CMJ medianvärde på 36.2 ± 7.48 cm. KTRL gruppen uppnådde ett IMTP (N) medianvärde på: 1626.9 ± 501.95N och ett CMJ medianvärde på: 31.8 ± 5.91cm. Ingen statistiskt signifikant skillnad hittades mellan grupperna, men traceurerna visar en trend för ett högre IMTP (N) värde. Ett statistiskt signifikant samband fanns mellan IMTP och CMJ för hela populationen. R-värde = 0.404. R² värde avrundades till 23%. P-värde = 0.031. Inget statistiskt signifikant samband fanns för PK eller KTRL grupperna individuellt. Slutsats: Traceurerna och de fysiskt aktiva högskolestudenterna visade snarlika resultat i maximal styrka och explosiv styrka i denna studie. Resultaten klassificerades som lågpresterande i förhållande till referensvärden från tidigare studier på traditionella idrotter för IMTP och på traceurer i CMJ. Den maximala styrkan från IMTP tycks förklara 23% av hoppförmågan i CMJ vilket kan vara en indikation av betydelse för traceurers prestation. Framtida forskare uppmuntras använda IMTP och CMJ på större populationer för att kartlägga traceurers force-velocity kurvor och/eller inrätta skadepreventiva program för PK/FR. Begrepp: Traceur (FRE) = tracer (ENG), spårare (SWE). Traceur = manlig Parkour utövare. Traceuse = kvinnlig Parkourutövare. PK/FR = Parkour/Freerunning. PK = Studiens Parkour grupp. KTRL = Studiens kontrollgrupp. Countermovement jump (CMJ), (N) = Newton. 1RM = en 100% maximal ansträngd repetition. / Purpose: The aim of the study was to investigate if IMTP together with CMJ can be considered as suitable methods to measure performance in jumping ability in PK/FR. We investigated this by measuring maximal strength and explosive strength of the lower extremities of traceurs and comparing the results with physically active college student athletes. We investigated also if IMTP and CMJ correlate with each other. Recruitment: 23 people, 11 traceurs and 12 psychical active collegial sport athletes were recruited for this study. Method: We measured maximal strength: PF IMTP (N) on force plate and maximal vertical jump height: CMJ (cm) on IR mat. Statistical analysis: Shapiro Wilks was used for normal distribution; an independent two-way Mann-Whitney U t-test was used to examine differences between groups. Linear regression tests with two Spearman's and one Pearson's correlation coefficient tests were used to examine relationships between IMTP and CMJ. R² values were calculated. Results: The PK group was normally distributed in IMTP (N) and CMJ (cm). The KTRL group was not normally distributed in CMJ (cm) and flagged an indication for IMTP (N). The PK group achieved a IMTP (N) median of 2269.9N SD ± 661.72N. And CMJ median of 36.2cm SD ± 7.48cm. The KTRL group achieved a IMTP (N) median of 1626.9N SD ± 501.95N. And a CMJ median of 31.8cm SD ± 5.91cm. No statistically significant differences were found between the groups. But the traceurs showed a trend for a higher IMTP (N) value. A statistically significant relationship was found between IMTP and CMJ for the entire population. R value = 0.404. R² value was rounded to 23%. P-value = 0.031. No statistically significant relationships were found for the PK- or the KTRL groups individually. Conclusion: The traceurs and the physically active college students were similar in maximal- and explosive strength in this study. The results were classified as low performance in comparison to previous studies of traditional sports on IMTP and on traceurs on CMJ. The maximal strength from the IMTP appears to account for 23% of the jumping ability in CMJ which may be an indication of importance for traceurs performance. Future researchers are encouraged to use IMTP and CMJ on larger populations to map force-velocity curves and/or establish injury prevention programs for PK/FR. Concepts: Traceur (FRE) = tracer (ENG), tracker (SWE). Traceur = male Parkour practitioner. Traceuse = female Parkour practitioner. PK/FR = Parkour/Freerunning. PK = The study's Parkour group. KTRL = Study control group. Countermovement jump (CMJ), Isometric mid-thigh pull (IMTP). 1 RM = a 100% maximum effort repetition. / <p>Ämneslärarprogrammet, Specialidrott</p>