Recent advancements in 3D data gathering have made it possible to measure the distance to an object at different time stamps through the use of time-of-flight cameras. Therefore, the purpose of this study was to investigate the validity and reliability of a time-of-flight camera on different mechanical sprint properties of the muscle. Fifteen male football players performed four 30m maximal sprint bouts which was simultaneously recorded with a time-of-flight camera and 1080 sprint device. By using an exponential function on the collected positional- and velocity-time data from both the devices, following variables were derived and analyzed: Maximal velocity (nmax), time constant (t), theoretical maximal force (F0), theoretical maximal velocity (V0), peak power output (Pmax), F-V mechanical profile (Sfv) and decrease in ratio of force (Drf). The results showed strong correlation in vmax along with a fairly small standard error of estimate (SEE) (r = 0,817, SEE = 0,27 m/s), while t displayed moderate correlation and relatively high SEE (r = 0,620, SEE = 0,12 s). Furthermore, moderate mean bias (>5%) were revealed for most of the variables, except for vmax and V0. The within-sessions reliability using Intraclass correlation coefficient (ICC) and standard error of measurement (SEM) ranged from excellent to poor with Pmax displaying excellent reliability (ICC = 0,91, SEM = 72W), while vmax demonstrated moderate reliability (ICC = 0,61, SEM = 0,26 m/s) and t poor(ICC = 0,44, SEM = 0,11 s). In conclusion, these findings showed that in its current state, the time-of-flight camera is not a reliable or valid device in estimating different mechanical properties of the muscle during sprint running using Samozino et al’s computations. Further development is needed.

Aim The aim of this study was to ascertain the effect of resisted sprint training in swimming on maximal swimming velocity and performance characteristics. The aim was also to examine how maximal swimming velocity is related to maximal swim power and maximal dry-land power. Method Eighteen competitive national level swimmers (9 male and 9 female; age: 18.3 ± 2.3 years, body mass: 72 ± 8.3 kg, height: 177.2 ± 4.6 cm, mean ± SD) were recruited to this study. Subjects were assigned to either resisted sprint training (RST) or unresisted sprint training (UST). Sprint training was performed two times per week during 6 weeks as 8x15m with a 2min send-off interval. RST performed sprint training using individualized load corresponding 10% of maximum drag load (L10), UST performed sprint training with no added resistance. A test-battery including dry-land strength assessment; maximal strength (MxS) and explosive strength (ExS), a timed 25m front-crawl swim and in-water force-velocity profiling was performed prior and following the training intervention. Maximal swim power (Pmax), maximum drag load (F0), theoretical maximum velocity (v0) and slope of force-velocity curve (SFv) was computed though force-velocity profiling. Results No significant within group differences occurred in neither RST nor UST following the 6-week intervention period in: swimming velocity, MxS, ExS, Pmax, F0, v0, and SFv. Strong correlations were found between swimming velocity and MxS (r = 0.75), ExS (r =0.82) and Pmax (r = 0.92). Conclusion Resisted sprint training in swimming using L10 did in the present study not elicit any improvements in maximal swimming velocity or examined performance characteristics. Resisted sprint training does not appear to be a superior method of improving swimming performance compared to unresisted sprint training. MxS, ExS and Pmax can be used as robust predictors of swim performance, however only Pmax was found to be casually related to swimming velocity.

Aim  The purposes of this study were to investigate if the load-velocity (L-V) profile parameters – force capacity and efficiency - differ between swimmers of different performance level, and to investigate if efficiency is the key performance indicator between international elite and national elite level swimmers.  Method  Fifty-four swimmers (27 female and 27 male) of either regional level, national elite or international elite level, participated in this study. The swimmers performed three 25 m semi- tethered maximum effort swims with ascending loads (1 kg, 5% and 10% of body mass). Mean velocity during three stroke cycles mid-effort was calculated and plotted as a function of the external added load. A linear regression was established, expressing the relationship between load and velocity, with the intercepts between the axes and the regression line being defined as the theoretical maximum velocity (V0) and load (force capacity, L0). The slope of the regression line (slopeLV) serves as an index of efficiency. Results A statistically significant difference was found between the three performance levels for all L- V profile variables for front crawl: V0 (F [2, 51] = 7.76, p<0.001), L0 (F [2, 51] = 5.18, p=0.009), and slopeLV (F [2, 51] = 3.36, p=0.043). A paired t-test revealed no difference in slopeLV between matched international elite and national elite level swimmers (t [9] = 1.42, p=0.188), but a near significant difference in L0 (t [9] = 2.11, p=0.064) . Both slopeLV and L0 for front crawl had a strong correlation with personal best in 100 m front crawl (PB100). Conclusion Efficiency was not found to be the key performance indicator between matched international elite and national elite swimmers in this study, and neither was force capacity. Nevertheless, a significant difference in all front crawl L-V profile parameters was found between performance level groups, but post hoc analyses indicated no difference between adjacent performance levels neither in L0 nor slopeLV. There was however a strong correlation between both slopeLV, and L0, to the swimmers’ PB100. All these findings imply that efficiency and force capacity seem to be of equal importance for high performance, but swimmers use different strategies to reach the high swim velocity. / Longitudinal development of performance determining factors in swimming (NIH)