Identifying Consistent Metrics from the Force-Time Curve of the Countermovement Jump in Combat Fighters and Physically Active Men

We investigated the consistency of metrics obtained from the unweighting, braking, propulsive, and landing phases of the countermovement (CMJ) force-time curve in combat fighters and physically active men. Combat fighters (n=21) and physically actives (n=21) were tested for three days (2-7 days apart). Participants performed four maximal CMJ separated by 1-min for between-day comparisons. From force-time recording, the consistency of 16 CMJ metrics (peak and mean ground reaction forces (GRF), net impulse, and duration from each phase) was investigated using the intraclass correlation coefficient (ICC) and typical error (CVTE). We considered as "consistent" those metrics showing no systematic differences, ICC ≥ 0.75, and CVTE ≤ 10%. We further compared the CVTE between groups and pairs of trials (days). Participants demonstrated more consistency in the braking and propulsive phases, while the unweighting phase did not show any consistent metric. There was no evidence of a learning effect (systematic changes), but analysis appointed more consistency on days 2-3 than on days 1-2 (18 metrics presented lower CVTE while 11 presented higher). We identified braking and propulsive GRF (peak and mean) and propulsive impulse as consistent metrics for combat fighters, while only propulsive impulse for physically actives. The between-group analyses showed that 24 comparisons favored the combat fighters against only five favoring the physically actives. In conclusion, force-time metrics related to jumping strategy, like phase duration, are less consistent than those related to driven forces and jump output, probably because participants changed their jump strategy during testing days.

Can Creatine Supplementation Interfere with Muscle Strength and Fatigue in Brazilian National Level Paralympic Powerlifting?

The aim of the present study was to analyze the effect of creatine (Cr) supplementation on peak torque (PT) and fatigue rate in Paralympic weightlifting athletes. Eight Paralympic powerlifting athletes participated in the study, with 25.40 ± 3.30 years and 70.30 ± 12.15 kg. The measurements of muscle strength, fatigue index (FI), peak torque (PT), force (kgf), force (N), rate of force development (RFD), and time to maximum isometric force (time) were determined by a Musclelab load cell. The study was performed in a single-blind manner, with subjects conducting the experiments first with placebo supplementation and then, following a 7-day washout period, beginning the same protocol with creatine supplementation for 7 days. This sequence was chosen because of the lengthy washout of creatine. Regarding the comparison between conditions, Cr supplementation did not show effects on the variables of muscle force, peak torque, RFD, and time to maximum isometric force (p > 0.05). However, when comparing the results of the moments with the use of Cr and placebo, a difference was observed for the FI after seven days (U³: 1.12; 95% CI: (0.03, 2.27); p = 0.02); therefore, the FI was higher for placebo. Creatine supplementation has a positive effect on the performance of Paralympic powerlifting athletes, reducing fatigue index, and keeping the force levels as well as PT.