Reliability of Xsens inertial measurement unit in measuring trunk accelerations: a sex-based differences study during incremental treadmill running

IntroductionInertial measurement units (IMUs) are utilized to measure trunk acceleration variables related to both running performances and rehabilitation purposes. This study examined both the reliability and sex-based differences of these variables during an incremental treadmill running test.MethodsEighteen endurance runners performed a test–retest on different days, and 30 runners (15 females) were recruited to analyze sex-based differences. Mediolateral (ML) and vertical (VT) trunk displacement and root mean square (RMS) accelerations were analyzed at 9, 15, and 21 km·h−1.ResultsNo significant differences were found between test-retests [effect size (ES)<0.50)]. Higher intraclass correlation coefficients (ICCs) were found in the trunk displacement (0.85-0.96) compared to the RMS-based variables (0.71–0.94). Male runners showed greater VT displacement (ES = 0.90–1.0), while female runners displayed greater ML displacement, RMS ML and anteroposterior (AP), and resultant euclidean scalar (RES) (ES = 0.83–1.9).DiscussionThe IMU was found reliable for the analysis of the studied trunk acceleration-based variables. This is the first study that reports different results concerning acceleration (RMS) and trunk displacement variables for a same axis in the analysis of sex-based differences

A “Blood Relationship” Between the Overlooked Minimum Lactate Equivalent and Maximal Lactate Steady State in Trained Runners. Back to the Old Days?

Maximal Lactate Steady State (MLSS) and Lactate Threshold (LT) are physiologically-related and fundamental concepts within the sports and exercise sciences. Literature supporting their relationship, however, is scarce. Among the recognized LTs, we were particularly interested in the disused “Minimum Lactate Equivalent” (LEmin), first described in the early 1980s. We hypothesized that velocity at LT, conceptually comprehended as in the old days (LEmin), could predict velocity at MLSS (VMLSS) more accurate than some other blood lactate-related thresholds (BLRTs) routinely used nowadays by many sport science practitioners. Thirteen male endurance-trained [VMLSS 15.0 ± 1.1 km·h−1; maximal oxygen uptake (VO2max) 67.6 ± 4.1 ml·kg−1·min−1] homogeneous (coefficient of variation: ≈7%) runners conducted 1) a submaximal discontinuous incremental running test to determine several BLRTs followed by a maximal ramp incremental running test for VO2max determination, and 2) several (4–5) constant velocity running tests to determine VMLSS with a precision of 0.20 km·h−1. Determined BLRTs include LEmin and LEmin-related LEmin plus 1 (LEmin+1mM) and 1.5 mmol·L−1 (LEmin+1.5mM), along with well-established BLRTs such as conventionally-calculated LT, Dmax and fixed blood lactate concentration thresholds. LEmin did not differ from LT (P = 0.71; ES: 0.08) and was 27% lower than MLSS (P < 0.001; ES: 3.54). LEmin+1mM was not different from MLSS (P = 0.47; ES: 0.09). LEmin was the best predictor of VMLSS (r = 0.91; P < 0.001; SEE = 0.47 km·h−1), followed by LEmin+1mM (r = 0.86; P < 0.001; SEE = 0.58 km·h−1) and LEmin+1.5mM (r = 0.84; P < 0.001; SEE = 0.86 km·h−1). There was no statistical difference between MLSS and estimated MLSS using LEmin prediction formula (P = 0.99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.45 km·h−1 and ±0.89 km·h−1. Additionally, LEmin, LEmin+1mM and LEmin+1.5mM were the best predictors of VO2max (r = 0.72–0.79; P < 0.001). These results support LEmin, an objective submaximal overlooked and underused BLRT, to be one of the best single MLSS predictors in endurance trained runners. Our study advocates factors controlling LEmin to be shared, at least partly, with those controlling MLSS

Reproducibilidad de diferentes test físicos en jugadores de baloncesto en silla de ruedas

Despite the fact that the physical actions of wheelchair basketball (WB) players during games implies many change of direction, sprints and repeated change of directions, to date there is no scientific publication reporting the reproducibility of different tests to measure this abilities WB. Seventeen players (15 male and 2 female; 25.9±9.7 yrs.) belonging to a Spanish First Division WB team volunteered. During the first in-season WB competitive week (Test), players performed 5 standardized physical tests. Tests were the 3-3-6 Test, 505 Test, Illinois Test, Repeated Sprint Ability (RSA) test and the Repeated Modified Agility T-test (rMAT). One week later (re-Test) players re-performed the tests using identical timing- and test-protocols. Change of direction ability tests’ results showed high reproducibility values [intraclass correlation coefficient (ICC) >0.74; coefficient of variation (CV) 0.90; CV0.94; CV0,74; CV0,90; CV0,94; CV<2,18±1,73%; SEM=0,27). Sin embargo, el índice de fatiga (Sdec) no mostró buenos valores de reproducibilidad ni en el RSA ni en el rMAT. Todos los test presentaron altos valores de reproducibilidad, por lo que podrían ser utilizados por los entrenadores y preparadores físicos como herramienta para evaluar la evolución de la capacidad física en jugadores de BSR