The paper is devoted to the problem of the determination of regular forces acting on microscopic and smaller objects in fluids when the presence of thermal noise affects the results of measurements. ...One of the methods on how these forces are determined is the measurement of the drift velocity of Brownian particles. Traditionally such experiments are interpreted on the basis of the overdamped Langevin equation. An exact expression has been obtained for this velocity within the linear hydrodynamic theory of the Brownian motion in incompressible fluids, when the external force is constant and when the particle is in a harmonic potential well. It is shown that for sufficiently short experimental times the influence of the hydrodynamic memory effects in the drift velocity determination is significant. The obtained solutions contain algebraic long-time tails due to which the results expected from the standard theory are approached very slowly with the increase of time.
ABSTRACTPickett, CW, Nosaka, K, Zois, J, and Blazevich, AJ. Relationships between midthigh pull force development and 200-m race performance in highly trained kayakers. J Strength Cond Res ...XX(X)000–000, 2019—While increased lower-limb force production during kayaking has been shown to be related to increased boat velocity, poor relationships between maximal deadlift test performances and 200-m race time have been observed previously. This discrepancy may result from either a lack of movement pattern or temporal force production specificity between the test and kayak paddling. The isometric midthigh pull (MTP) test is commonly used in strength testing and quantifies temporal and peak force production, with the lower limbs positioned in a more kayak-specific manner than the deadlift test. Midthigh pull force data collected from 11 high-level kayak athletes were analyzed for both reliability and correlations with 200-m race time and deadlift isoinertial strength 3 repetition maximum (3RM). Strong consideration was given to the collection, processing, and analysis of the MTP data, which markedly affected the study results. Correlations between race time and MTP peak force and rates of force development were poor to moderate (r = −0.49 to 0.07). Strong to very strong relationships (r = 0.66–0.79) were found between forces developed early in the MTP (<0.15 seconds) and deadlift 3RM strength tests but were poor for later time-specific force development (r ≤ 0.12). However, poor reliability was found for force measured up to ≤0.25 seconds from the point of force onset (intraclass correlation coefficient >0.8). Owing to the relatively weak relationships with 200-m race time, and the large variability of the data, it may not be wise to include the MTP in the testing and training of 200-m kayak athletes.
