Understanding the influence of running-induced acute fatigue on the homeostasis of the body is essential to mitigate the adverse effects and optimize positive adaptations to training. Fatigue is a multifactorial phenomenon, which influences biomechanical, physiological, and psychological facets. This work aimed to assess the evolution of these three facets with acute fatigue during a half-marathon. 13 recreational runners were equipped with one inertial measurement unit (IMU) on each foot, one combined global navigation satellite system-IMU-electrocardiogram sensor on the chest, and an Android smartphone equipped with an audio recording application. Spatio-temporal parameters for the running gait, along with the heart rate, its variability and complexity were computed using validated algorithms. Perceived fatigability was assessed using the rating-of-fatigue (ROF) scale at every 10 min of the race. The data was split into eight equal segments, corresponding to at least one ROF value per segment, and only level running parts were retained for analysis. During the race, contact time, duty factor, and trunk anteroposterior acceleration increased, and the foot strike angle and vertical stiffness decreased significantly. Heart rate showed a progressive increase, while the metrics for heart rate variability and complexity decreased during the race. The biomechanical parameters showed a significant alteration even with a small change in perceived fatigue, whereas the heart rate dynamics altered at higher changes. When divided into two groups, the slower runners presented a higher change in heart rate dynamics throughout the race than the faster runners; they both showed similar trends for the gait parameters. When tested for linear and non-linear correlations, heart rate had the highest association with biomechanical parameters, while the trunk anteroposterior acceleration had the lowest association with heart rate dynamics. These results indicate the ability of faster runners to better judge their physiological limits and hint toward a higher sensitivity of perceived fatigue to neuromuscular changes in the running gait. This study highlights measurable influences of acute fatigue, which can be studied only through concurrent measurement of biomechanical, physiological, and psychological facets of running in real-world conditions.

Recent advances in wearable technologies integrating multi-modal sensors have enabled the in-field monitoring of several physiological metrics. In sport applications, wearable devices have been widely used to improve performance while minimizing the risk of injuries and illness. The objective of this project is to estimate breathing rate (BR) from respiratory sinus arrhythmia (RSA) using heart rate (HR) recorded with a chest belt during physical activities, yielding additional physiological insight without the need of an additional sensor. Thirty-one healthy adults performed a run at increasing speed until exhaustion on an instrumented treadmill. RR intervals were measured using the Polar H10 HR monitoring system attached to a chest belt. A metabolic measurement system was used as a reference to evaluate the accuracy of the BR estimation. The evaluation of the algorithms consisted of exploring two pre-processing methods (band-pass filters and relative RR intervals transformation) with different instantaneous frequency tracking algorithms (short-term Fourier transform, single frequency tracking, harmonic frequency tracking and peak detection). The two most accurate BR estimations were achieved by combining band-pass filters with short-term Fourier transform, and relative RR intervals transformation with harmonic frequency tracking, showing 5.5% and 7.6% errors, respectively. These two methods were found to provide reasonably accurate BR estimation over a wide range of breathing frequency. Future challenges consist in applying/validating our approaches during in-field endurance running in the context of fatigue assessment.

Walking activity and gait parameters are considered among the most relevant mobility-related parameters. Currently, gait assessments have been mainly analyzed in laboratory or hospital settings, which only partially reflect usual performance (i.e., real world behavior). In this study, we aim to validate a robust walking detection algorithm using a single foot-worn inertial measurement unit (IMU) in real-life settings. We used a challenging dataset including 18 individuals performing free-living activities. A multi-sensor wearable system including pressure insoles, multiple IMUs, and infrared distance sensors (INDIP) was used as reference. Accurate walking detection was obtained, with sensitivity and specificity of 98 and 91% respectively. As robust walking detection is needed for ambulatory monitoring to complete the processing pipeline from raw recorded data to walking/mobility outcomes, a validated algorithm would pave the way for assessing patient performance and gait quality in real-world conditions. Graphical Abstract

The recent tightening of regulations on the polybrominated diphenyl ethers (PBDEs) production has led to an increase in the use of organophosphate flame retardants (OPFR). Although several toxicological studies suggest that these chemicals can disrupt thyroid homeostasis, epidemiological studies remain sparse. This work aims to investigate the associations between prenatal OPFR exposure and thyroid hormone levels in mothers and their newborns. The study population consisted of 442 mother-child pairs from the French SEPAGES cohort recruited between 2014 and 2017. Four OPFR metabolites -diphenyl phosphate (DPhP), di-n-butyl phosphate (DNBP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and bis(2-butoxyethyl) phosphate (BBOEP) -were measured in two pools of multiple urine samples collected during the second and third trimesters of pregnancy. Thyroid hormones were measured in maternal sera at the second trimester, and in newborns from a heel-prick blood spot. Adjusted linear regression models were used to assess the associations between each OPFR metabolite and each thyroid hormone. Maternal urinary iodine, child's sex, and exposure window were considered in additional analyses as potential effect modifiers. DNBP and BDCIPP were positively associated with newborn total thyroxine (TT4) and tended to be negatively associated with maternal total triiodothyronine (TT3). DPhP concentrations were also negatively associated with maternal thyroid stimulating hormone (TSH) levels. Our results suggest that exposure to OPFR could influence thyroid hormone levels in pregnant women and their newborns, raising concerns about potential adverse impacts on fetal development and postnatal health.

Organophosphate esters (OPEs) are widely used as flame-retardants and plasticizers in electronics, construction material, furniture and textiles. Studies investigating their neurodevelopmental effects suffer from exposure misclassification due to reliance on spot samples. Moreover, exposure during infancy, a critical developmental period, has not been assessed. To examine associations between pregnancy and infancy exposure to OPEs and children's Intelligence Quotient (IQ) scores at 3 years using repeated urine samples. In the SEPAGES cohort, urinary concentrations of 4 (pregnancy) to 9 (infancy) OPEs metabolites were measured in samples collected during the second and third trimesters of pregnancy, and at one year of age. IQ was assessed at 3 years by trained neuropsychologists. Sample size ranged from 343 to 375 across exposure periods. Associations between each OPE and IQ score were studied using adjusted linear regression models. Diphenyl phosphate (DPHP) showed the highest detection frequency and median at all timepoints. Detection of bis(2-butoxyethyl) phosphate (BBOEP) in the second trimester was associated with lower full-scale (β: 4.58 points, 95% confidence interval (CI): 8.52; -0.64), verbal (β: 5.55, 95%CI: 9.63; -1.47) IQ and tended to be associated with working memory scores. At one year, urinary diisobutyl phosphate (DIBP) and bis(2-chloroisopropyl) phosphate (BCIPP) concentrations were positively associated with full-scale and verbal IQ. BBOEP results matched prior findings but require replication given few available studies and low detection frequency in our cohort. This first study including infancy exposure did not suggest deleterious association for this period, but further investigations are needed as infants exhibited higher concentrations than their mothers.

The recent tightening of regulations on the polybrominated diphenyl ethers (PBDEs) production has led to an increase in the use of organophosphate flame-retardants (OPFR). Although several toxicological studies suggest these chemicals to disrupt thyroid homeostasis, epidemiological studies remain sparse. This work aims to investigate the associations between prenatal OPFR exposure and thyroid hormone levels in mothers and their newborns. In 442 mother‑child pairs from the French SEPAGES cohort recruited between 2014 and 2017. Four OPFR metabolites —diphenyl phosphate (DPhP), di‑n‑butyl phosphate (DNBP), bis(1,3‑dichloro‑2‑propyl) phosphate (BDCIPP), and bis(2‑butoxyethyl) phosphate (BBOEP) —were measured in two pools of multiple urine samples collected during the second and third trimesters of pregnancy. Thyroid hormones were measured in maternal sera at the second trimester, and in newborns from a heel-prick blood spot. Adjusted linear regression models were used to assess the associations between each OPFR metabolite and each thyroid hormone. Maternal urinary iodine, child’s sex, and exposure window were considered in additional analyses as potential effect modifiers. DNBP and BDCIPP were negatively associated with maternal total triiodothyronine (TT3), and positively associated with newborn total thyroxine (TT4). A negative association was also observed between DPhP concentrations and maternal thyroid stimulating hormone (TSH). Our results suggest that exposure to OPFR metabolites may disrupt thyroid hormone homeostasis in pregnant women and their newborns, raising concerns about potential adverse impacts on fetal development and postnatal health.