Muscle and kidney injury in endurance athletes is worrying for health, and its relationship with physical external workload (eWL) needs to be explored. This study aimed to analyze which eWL indexes have more influence on muscle and kidney injury biomarkers. 20 well-trained trail runners (age = 38.95 ± 9.99 years) ran ~35.27 km (thermal-index = 23.2 ± 1.8 °C, cumulative-ascend = 1815 m) wearing inertial measurement units (IMU) in six different spots (malleolus peroneus [MP_left/MP_right], vastus lateralis [VL_left/VL_right], lumbar [L₁–L₃], thoracic [T₂–T₄]) for eWL measuring using a special suit. Muscle and kidney injury serum biomarkers (creatin-kinase [sCK], creatinine (sCr), ureic-nitrogen (sBUN), albumin [sALB]) were assessed pre-, -post_0h and post_24h. A principal component (PC) analysis was performed in each IMU spot to extract the main variables that could explain eWL variance. After extraction, PC factors were inputted in multiple regression analysis to explain biomarkers delta change percentage (Δ%). sCK, sCr, sBUN, sALB presented large differences (p < 0.05) between measurements (pre < post_24h < post_0h). PC’s explained 77.5–86.5% of total eWL variance. sCK Δ% was predicted in 40 to 47% by L₁–L₃ and MP_left; sCr Δ% in 27% to 45% by L₁–L₃ and MP_left; and sBUN Δ% in 38%-40% by MP_right and MP_left. These findings could lead to a better comprehension of how eWL (impacts, player load and approximated entropy) could predict acute kidney and muscle injury. These findings support the new hypothesis of mechanical kidney injury during trail running based on L₁–L₃ external workload data.

With the development of new microsensor technology to assess load in sports, some indicators of external load through accelerometry-based data have been created by sport technology companies. Thus, the study aim was to analyze the agreement between different accelerometry-based external load indicators (ABELIs) available in sport science. A U-16 male soccer team was assessed during three official matches, divided by periods, to obtain 3-D accelerometry data (x, y and z axes). An average of 1,420,000 data points was analyzed per axis per player. The ABELIs were calculated using this information, and the agreement between them was explored. The following ABELIs were considered after a literature review: AcelT, Player Load_RT, PlayerLoad^TM, Impulse Load, Player Load_RE and Total Load. In order to compare ABELIs, two analyses were performed using: (1) absolute data; and (2) normalized and centered data (Z-scores). In absolute and centered data, very large to nearly perfect correlations (1st period: r > 0.803, p > 0.01; 2nd period: r > 0.919; p > 0.01) were found. Instead, very large differences were found in absolute values (bias = −579,226.6 to 285,931.1; t = −224.66 to 213.91, p < 0.01), and no differences in scaled and centered values (bias = 0; t = 1; p = 1). In conclusion, considering the different output (magnitude and units) among ABELIs, the standardization of a universal index to calculate accelerometer load is needed in order to make possible between-study comparison.

Background: Body temperature is often assessed in the core and the skin. Infrared thermography has been used to measure skin temperature (Tsk) in sport research and clinical practice. This study aimed to explore the information reported to date on the use of infrared thermography to detect short-term Tsk responses to endurance exercise and to identify the methodological considerations and knowledge gaps, and propose future directions. Method: A web search (PubMed, Science Direct, Google Scholar, and Web of Science) was conducted following systematic review guidelines, and 45 out of 2921 studies met the inclusion criteria (endurance sports, since 2000, English, full text available). Results: A total of 45 publications were extracted, in which most of the sample were runners (n = 457, 57.9%). Several differences between IRT imaging protocols and ROI selection could lead to potential heterogeneity of interpretations. These particularities in the methodology of the studies extracted are widely discussed in this systematic review. Conclusions: More analyses should be made considering different sports, exercise stimuli and intensities, especially using follow-up designs. Study-derived data could clarify the underlying thermo physiological processes and assess whether Tsk could be used a reliable proxy to describe live thermal regulation in endurance athletes and reduce their risk of exertional heat illness/stroke. Also more in-depth analyses may elucidate the Tsk interactions with other tissues during exercise-related responses, such as inflammation, damage, or pain.

In recent decades, the search for non-doping substances that enhance sports performance has increased. Ergogenic aids such as beetroot juice (BRJ) and BRJ rich in nitrates (NO₃^-) are widely used to cause physiological benefits that may lead to physical improvements. Therefore, the purpose of this systematic review was to explore the knowledge reported to date on the NO₃^- derived from BRJ intake effect on fatigue resistance during repeated sprints. A digital search was conducted following systematic review guidelines, and 18 studies met inclusion criteria from a total of 209 articles. In a third of the selected studies, the consumption of beet juice rich in NO₃^- contributes to an increase in nitrites in plasma that led to the rise in peak power, mean power, number of sprint repetitions, total work and time to task failure, and causes a decrease in fatigue index and sprints times. Some different dose has been proposed for both chronic and acute protocols. It seems that a chronic intake of ∼5-6 mmol of NO₃^- in 70 ml of BRJ, twice a day, for a minimum of 3-6 days could lead to a fatigue resistance improvement during repeated sprints. Besides, acute intake of NO₃^- 2.5-3 h before physical exertion or a dose of 250 ml/d to 500 ml/d of BRJ could lead to similar effective results. This systematic review presents some improvements (1.2-5.38%) in fatigue resistance during repeated sprints when consuming BRJ derived NO₃^-. The in-field practical meaning of these results should be explored.

Cold water immersion (CWI) has become a highly used recovery method in sports sciences, which seeks to minimize fatigue and accelerate recovery processes; however, few studies have used tensiomyography (TMG) is a new method to analyze the muscle mechanical response as a recovery indicator after CWI protocols, this relative new tool of muscle function assessment, can lead to new information of understand fatigue recovery trough CWI. The objective of the study was to compare the effect of two CWI protocols, on neuromuscular function recovery. Thirty-nine healthy males (21.8 ± 2.876 yrs., 73.215 ± 8.215kg, 176.6 ± 5.3 cm and body fat 13.5 ± 3.4%.%) were included in the study. Participants were grouped into a continuous immersion (12 min at 12 ± 0.4 °C) group, intermittent immersion (2 min immersion at 12 ± 0.4 °C + 1 min out of water 23 ± 0.5 °C) group, and a control group (CG) (12 min sitting in a room at 23 ± 0.5 °C). Afterwards, the participants performed eight sets of 30 sec counter movement jumps (CMJ) repetitions, with a 90 s standing recovery between sets. Muscle contraction time (Tc), delay time (Td), muscle radial displacement (Dm), muscle contraction velocity at 10% of DM (V10), and muscle contraction velocity at 90% of DM (V90) in rectus, biceps femoris, and CMJ were measured. Neither CWI protocol was effective in showing improved recovery at 24 and 48 hours after training compared with the CG (p > .05), in any TMG indicator of recovery in either muscle biceps or rectus femoris, nor was the CMJ performance (F(6,111) = 0.43, p = .85, ωp2 = 0). Neither CWI protocol contributed to recovery of the neuromuscular function indicator.

Objectives: The main objective of this study was to compare two cold water immersion protocols, continuous or intermittent, on recovery in basketball players. Methods: Ten male basketball players (age: 14 ± 0.4 years, body mass: 65.4 ± 9.1 kg, height: 175 ± 7.3 cm, body fat %: 10.3 ± 4) were included in the study. After three 90-minute training sessions (avg. heart rate 158 ± 11.92, 156 ± 7.06 and 151 ± 10.44 bpm), participants were grouped into a continuous immersion (12 min at 12 ± 0.4°C) group, intermittent immersion (4 x 2 min immersion at 12 ± 0.4 °C + 1 min out of water) group and a control group (CG). Countermovement jump (CMJ), muscle pain and thigh volume were measured. Results: Both cold water immersion protocols were effective in reducing the pain 24 and 48 hours after training compared with the CG (F (3.54) = 2.91, p = 0.016, η_p² = .24). Concerning CMJ change, % differences occurred at 24 (Z = 11.04, p = 0.004) and 48 hours (Z = 14.01, p < 0.001) in comparison with the CG. Regarding the muscle volume, the statistical analysis did not report a significant interaction (F (3.54) = 2.42, p = 0.058). Conclusion: Both cold water immersion CWI protocols are effective in improving recovery in basketball players.