This study aims to verify the validity of the Push Band 2.0 (PB2.0) device on the reactive strength index (RSI) measurement, using a force plate (FP) and an optical sensor device, OptoJump (OPT), as a reference. Twenty trained athletes performed 60 drop jump trials with a height box of 30 cm. A randomized repeated measures study was conducted during a single session using the PB2.0, the OPT, and the plate force manually synchronized to obtain RSI data for each jump. Validity was analyzed by contrasting three measures: the intra-class correlation coefficient (ICC), the Bland–Altman test, and R2 coefficient of determination. Bland–Altman analysis showed that RSI and FP for PB2.0 (media = −0.047; IC 93.34%) of all data were within the confidence interval, indicating a statistically reliable result. The RSI measured by the OPT and PB2.0 also provided similar values (media = −0.047). These data are identical to other validity measures (ICC and linear correlation) but differ in the R2 values. The explained variation of PB2.0 measures attained only 29.3% of the FP (R2 = 0.293) and 29.5% (R2 = 0.295) of the OPT assessment, showing a very low determination coefficient. The results of this study point to caution in the use of PB2.0 when measuring RSI in scientific research.
This study analyzes the strategy used by the best male runners who participated in one of the major city marathons (Frankfurt Marathon, 2008‐2018), the all‐time performances <2:04:00, the male world records achieved during the 21st century and the Nike Breaking2 Project and INEOS 1:59 Challenge (total = 235 races). The races of the best runners in the Frankfurt Marathon (top 10) were analyzed (n = 110 runners, range: 2:03:42‐2:14:05 hours); the runners were divided into two groups according to the tactical used. The pace of Group A (stable pace) remained steady throughout the race, while in Group B (decrease in running speed toward the end of the race) a moderate, but significant drop in speed was detected (P ≤ .001), starting from halfway through the race and getting sharper from the 30th kilometer (30‐35 km = 1.6%, P ≤ .001 – 35‐40 km = 4.3%, P ≤ .001 – 40‐42.195 km: 3.9%, P ≤ .001, total = ≈10%). In the races in which the world record is achieved, the running speed tends to be steady and relatively conservative during the first stretch of the race, increasing smoothly in the second half and achieving a significant increase in the last 2195 m of the race (P = .016, ES = 1.14). Among all the possible strategies, running at a steady pace throughout the race seems the most effective option, especially when priority is given to time rather than position (ie, world records and best all‐time races).
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