# Power Up: Comparing PAPE Responses in Free-Weight vs. Flywheel Resistance Training Systems
## 2 Materials and Methods
### Design and Intensity Matching  
This study followed a randomized crossover design, where participants attended the laboratory once per week for 3 weeks at approximately the same time of day and under the same environmental conditions. Participants were instructed to avoid strenuous physical activity for at least 24 h and avoid caffeine for 3 h before the experimental sessions. The purpose of session one was to match the half-squat concentric intensity between free-weight and flywheel devices using MPV. MPV is defined as a fraction of the concentric phase during which barbell acceleration was greater than the acceleration because of gravity. Vertical velocity was measured via a linear encoder (SmartCoach Power Encoder, SmartCoach Europe AB, Stockholm, Sweden) attached to the harness worn by the participants during both free-weight and flywheel exercises.  
The schematic representation and timeline of the study design are shown in Figure 1. First, each participant warmed up with 5 min jogging at a self-selected sub-maximal pace, one set of ten bodyweight half-squats, and eight submaximal flywheel half-squat repetitions with a moment of inertia of 0.055 kg\(\cdot\)m\({}^{2}\) (Twister Pulley: Element Sport, Cadiz, Spain). The flywheel was anchored to a harness fastened on both shoulders and at the waist. Subsequently, participants performed ten repetitions with the same moment of inertia. Because the flywheel moment of inertia has little effect on acute performance enhancement magnitude on average at the group level [2], 0.055 kg\(\cdot\)m\({}^{2}\) was selected as the greatest intensity that the whole group could comfortably perform. The first two repetitions were  
\begin{table}
\begin{tabular}{c c} \hline \hline  & **n = 30** \\ \hline
**Age (years)** & 25.4 \(\pm\) 2.9 \\
**Height (cm)** & 176.2 \(\pm\) 7.6 \\
**Weight (kg)** & 76.9 \(\pm\) 9.9 \\
**1 RM (kg)** & 100.0 \(\pm\) 15.7 \\ \hline \hline \end{tabular} Data is presented as mean \(\pm\) SD.  
\end{table}
Table 1: Anthropometric descriptive characteristics and strength values of the participating subjects.  
performed submaximally to establish rhythm, while the remaining eight repetitions were maximal. The eccentric action was executed by gently resisting in the first third of the action and then aiming to stop the device when the thighs were parallel to the ground. The fastest MPV of the set was recorded for future analysis. After four minutes of rest, participants performed an incremental half-squat test in a [PERSON] machine (free-weight condition) (Multipower Fitness Line; Peroga, Murcia, Spain). Participants performed the free-weight exercise from an upright position, descending at a self-controlled velocity until the thighs were parallel to the ground, then immediately reversing the motion and ascending back to the upright position with maximal intended velocity. An initial load of 30 kg was progressively increased in 10 kg increments until the attained repetition MPV was \(<\) 0.68 m\(\cdot\)s\({}^{-1}\)[23]. One set of three repetitions was performed for light loads (\(\geq\)1.14 m\(\cdot\)s\({}^{-1}\)), and only two repetitions were performed for moderate loads (\(<\)1.14 m\(\cdot\)s\({}^{-1}\)), with between-load recovery times of 3 and 4 min [23], respectively. The fastest MPV of each set was recorded, and individual linear regressions between load and MPV were used to establish the absolute free-weight load for each participant to attain the same MPV as with the flywheel device. The average R\({}^{2}\) value for the individual regressions was 0.99.