Intra-session reliability of electromyographic measurements in flywheel squats

Abstract

Although the popularity of flywheel (FW) devices in sports research is increasing, to date, no study has been designed to test the reliability of electromyographic (EMG) variables during FW squats as a basic lower-body FW resistance exercise. At the primary level, our study was conducted to determine the minimum number of the consecutive flywheel (FW) squat repetitions that need to be averaged in a single set to obtain excellent reliability of peak, mean and three position-specific EMG variables. At the secondary level, comprehensive analysis for peak and mean EMG variables was done. Intra-set reliability was investigated using the minimum number of repetitions determined from the primary level of the study. Twenty-six participants performed five sets of seven squats with three FW loads (0.05, 0.125, 0.225 kg∙m2). EMG signals were collected from eight leg muscles. By averaging twelve consecutive repetitions, we obtained ICC2.k > 0.95 for mean and peak EMGRMS regardless of the muscle, load or phase of the squat (concentric vs. eccentric). Due to the heterogeneity of the results at the primary level, position-specific variables were excluded from the inter-set reliability analysis at the secondary level. Trustworthy mean and peak EMG variables from the primary level showed good to excellent inter-set reliability. We suggest averaging twelve consecutive squat repetitions to achieve good to excellent intra-session reliability of EMG variables. By following the proposed protocol, activation of leg muscles can be confidently studied in intra-session repeated-measures study designs.

Effects of flywheel resistance training on the running economy of young male well-trained distance runners

“…Each session the strength training was comprised of 4 sets of barbell squat exercises (6 reps) using 85% of 1 repetition maximum (RM). Participants were asked to squat until their thighs were parallel to the floor and push as hard and fast as possible ( Sagelv et al, 2020 ; Spudić et al, 2020 ). A 3-min rest was given between sets of an exercise to allow complete recovery.…”

“…Participants were asked to squat until their thighs were parallel to the floor and push as hard and fast as possible (Sagelv et al, 2020;Spudić et al, 2020). A 3-min rest was given between sets of an exercise to allow complete recovery.…”

Muscle Activation Sequence in Flywheel Squats

“…All squat repetitions were then extrapolated based on the trigger delivered by the lowest vertical squat position (approximately 90-degree knee angle) from the raw position-time data of each repetition. Data were time normalized and averaged based on twelve consecutive squats to get credible results of muscle EMG signal [ 38 ] and to permit improvement of the signal-to-noise ratio [ 43 ]. Outcome variables were calculated with the use of algorithms implemented in the time domain.…”

“…As described in FW squats, an increase in FW loading condition results in a linear increase in force output and a simultaneous decrease in movement velocity [ 37 ]. It has also been found that increased external FW resistance does not necessarily induce an increase in muscle activity level [ 38 ]. During isometric contractions, the level of external load may influence the relative contribution of synergistic muscles to the force output [ 39 ].…”

Effects of Relative Inertial Load on Quadriceps Electromyography during Maximal Effort Flywheel-based Iso-Inertial Training (FIT) Squats

“…Since peak EMG activity occurred during the brief isometric period during the eccentric-concentric transition, mean EMG amplitude of the concentric and eccentric phases were analyzed independently. Spudic et al 18 have recently reported high intra-session reliability (ICC > 0.95) for peak and mean EMG activity of the concentric and eccentric phases of five consecutive repetitions of the FIT squat. In our dataset, EMG activity was highly reproducible between repetitions (CV = 7.4, 8.0, and 9.2% for mean CON, mean ECC, and peak EMG activity, respectively).…”