Mixed
The unilateral exercise model (training one limb while keeping the contralateral limb as a control) significantly increases statistical power and reduces study costs compared to parallel-group or standard crossover designs by eliminating inter-subject variability and the need for washout periods.
For researchers, using a unilateral exercise model (training one limb while keeping the other as a control) is a highly efficient way to study muscle adaptations. It allows you to use fewer participants, reduces costs (fewer biopsies, less food provision), and eliminates the need for long washout periods between treatments, provided you are studying biochemical or histological outcomes rather than systemic or neuromuscular strength transfers.
The unilateral exercise model and crossover design share the same primary advantage compared to parallel group designs: the lack of inter-subject variability reduces the required sample size to obtain adequate statistical power in outcomes of interest... The unilateral exercise model usually does not require a washout period between treatments... enabling treatments to be delivered almost concurrently or at least temporally close to each other.
Why this rating
This is a review paper citing numerous primary studies and established statistical principles.
Source
Investigating human skeletal muscle physiology with unilateral exercise models: when one limb is more powerful than two
Martin J. MacInnis et al. · Applied Physiology Nutrition and Metabolism · 2017
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