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Crossover and Repeated Measures Designs
Published in John Lawson, Design and Analysis of Experiments with R, 2014
As an example of a simple AB, BA crossover study, consider the data reported by Wallenstein and Fisher (1977) from a clinical trial comparing the plasma levels of two formulations of an antifungal agent. Seventeen normal male volunteers were randomly assigned to two groups. The first group received formulation A for 13 days, followed by a 13-day washout period, and then formulation B for 13 days. Group two received the treatments in the B,A order. The response shown was the area under the 12-hour plasma curve taken on the last day of each period.
The perceptual responses to high-velocity, low-load and low-velocity, high-load resistance exercise in older adults
Published in Journal of Sports Sciences, 2018
Darren L. Richardson, Michael J. Duncan, Alfonso Jimenez, Victoria M. Jones, Paul M. Juris, Neil D. Clarke
The present study used a randomised, counterbalanced, crossover study design. Participants were randomised to complete both HVLL and LVHL, volume-load (repetitions x sets x relative load) matched conditions (identical total load lifted). The HVLL condition used 40% predicted one repetition maximum (1-RM) for three sets of 14 repetitions, with the concentric phase performed “as fast as possible” without causing dangerous unloading of the weight stack, followed by a 3 s eccentric phase. Whereas, the LVHL condition used 80% predicted 1-RM for three sets of seven repetitions, over a 2 s concentric phase and a 3 eccentric phase. Both conditions had 2 min of recovery between sets, and 3 min of recovery between exercises. A metronome was used to provide the cadence for exercise, excluding during the concentric phase of the HVLL condition. Each participant completed three sessions of HVLL and three sessions of LVHL, each separated by three days of recovery. Both conditions were based on others that have previously demonstrated a positive impact on functional performance in older adults (Kalapotharakos, Michalopoulos, Tokmakidis, Godolias, & Gourgoulis, 2005; Reid et al., 2015), with the number of sets and repetitions being similar to others that have attempted to match volume-loads (Hortobagyi, Tunnel, Moody, Beam, & DeVita, 2001; Sayers & Gibson, 2014). The two conditions were designed to be as simple and pragmatic as possible to provide a direct comparison of the perception of volume-load matched HVLL and LVHL.
The impact of different seats and whole-body vibration exposures on truck driver vigilance and discomfort
Published in Ergonomics, 2018
Bronson Boi Du, Philip L. Bigelow, Richard P. Wells, Hugh W. Davies, Peter Hall, Peter W. Johnson
Within-subject crossover study designs are advantageous as measures are taken from the same individuals across different conditions. Therefore, individual factors such as gender, age, general health and well-being, and lifestyle habits; operational factors such as schedules, routes and duties; and environmental factor such as cabin design, and road conditions were similar, if not identical, between the two seating conditions. Further, WBV exposures also showed significant differences between the seats allowing us to better isolate the effects of WBV exposure on vigilance and discomfort while remaining in a field environment.