Care was taken to ensure identical study conditions and uniformity in regard to time of day, location, equipment and procedure. Furthermore, all tests were conducted in a temperature-controlled environment with a single observer assessment and measurements regime maintained throughout the study. The same investigator (JBP), who was blinded to the intensity level, determined all threshold values and MR conducted all on-line muscle force measurements. To ensure optimal comparison between the two experimental secessions subjects were placed in a standardized position securing uniformity of posture, joint positions and orientation of the thigh. To reduce day-to-day variations in electrode placement on the thigh, these were marked, along with at least three permanent landmarks, on a transparent paper, thus serving as a "map" for a precise identification. On day seven the same investigator (JBP) then carefully replaced the electrodes identical to day 1. On both testing days, gauges were calibrated and each subject received a short standardized low intensity familiarisation session prior to the testing procedure to ensure potentiation of muscle tissue during which electrical muscle stimulation and the present protocol were carefully explained. Left/right testing order was determined after randomisation with the same order of testing maintained on the second experimental day. Subjects were instructed to be as relaxed as possible and to suppress any voluntary contraction during the test. Finally, to ensure the quality of the recorded data, knee extension forces were immediately displayed on-line on a computer screen for visual inspection.