Wiley: Scandinavian Journal of Medicine & Science in Sports: Table of Contents

Core Temperature Estimation Using Wearable Earbud‐Type Thermometer and Machine Learning During Light‐Intensity Cycling Under Varying Indoor Ambient Temperatures

Mon, 08 Jun 2026 06:15:24 -0700

ABSTRACT

Continuous monitoring of core temperature is crucial for optimizing exercise performance, promoting health, and ensuring safety. Here, we evaluated the validity of a machine learning-based earbud-type core temperature sensor during exercise. At ambient temperatures of 10°C, 20°C, and 30°C, participants rested and then cycled for 25 min (90 W for males and 60 W for females), with an artificial wind of ~3.0 m/s directed at the face during the final 10 min of exercise. Throughout the experiment, two thermistors embedded in the earbud-type device monitored both ambient temperature and internal ear temperature. Additionally, an infrared temperature sensor integrated into the earbud-type thermistor measured internal ear temperature. Core temperature was measured through a machine learning-based approach, and esophageal temperature served as the reference. We created mixed-effects Bland–Altman plots for the relationship between estimated and esophageal temperature, and found that the bias was −0.003°C with a limit of agreement of −0.52°C–0.51°C. Root mean squared error and Pearson's r for the two-temperature relationship were 0.26°C and 0.81, and 76.9% of the data exhibited temperature differences within a margin of ≤ 0.3°C between the two measurements. Similar results were also observed with artificial wind. Including infrared temperature measurements did not enhance the aforementioned variables. We show that a machine learning-based wearable earbud-type thermometer can validly estimate core temperature in exercising individuals across 10°C–30°C indoor ambient temperatures with and without exposure to a wind speed of ~3.0 m/s. However, further improvement of the algorithm is needed to enhance estimation accuracy.

Acute Sleep Deprivation Shifts Substrate Utilization Toward Greater Fat Oxidation During Incremental Exercise in Recreationally Trained Adults

Mon, 01 Jun 2026 06:14:57 -0700

ABSTRACT

Sleep deprivation alters metabolic homeostasis and substrate metabolism, but its effect on fat and carbohydrate utilization during exercise is unclear. This study examined the effects of one night of total and partial sleep deprivation on substrate utilization during a maximal fat oxidation test (MFO) in recreationally trained adults. Thirty-two recreationally trained young adults (16 females, 16 males) completed a randomized, counterbalanced crossover study with three sleep conditions: normal sleep (NS, 8 h), early sleep deprivation (ESD, 4 h), and total sleep deprivation (SD, 0 h). Sleep was monitored by wrist actigraphy and a researcher. The following morning, participants performed an incremental cycling test to determine MFO and carbohydrate oxidation (MCHO), absolute and relative to fat-free mass (FFM), Fat_max, and energy expenditure. Sleep condition affected MFO, ΜFO/FFM, MCHO, and MCHO/FFM (p < 0.05, η _p ² > 0.137). Compared with ESD and NS, SD increased MFO (9% and 16%, p < 0.001, g = 0.54) and MFO/FFM (9% and 15%, p = 0.003, g = 0.61). MCHO (−14%, p = 0.041, g = 0.41) and MCHO/FFM (−15%, p = 0.035, g = 0.53) decreased in SD compared to NS. No differences were observed in Fat_max or energy expenditure. Sleep restriction increased resting heart rate (~5%, p = 0.027, η _p ² = 0.114) and systolic blood pressure (~6%, p = 0.014, η _p ² = 0.139). Subjective fatigue, confusion, sleepiness, and perceived exertion were higher after total sleep deprivation (p < 0.001). No sleep-by-sex interactions were observed. One night of total sleep deprivation shifts exercise substrate utilization toward greater fat oxidation and lower carbohydrate use without affecting Fat_max or energy expenditure. However, increased fatigue and perceived effort highlight the importance of adequate sleep for optimal exercise performance.

Trial Registration: ClinicalTrial.gov identifier: NCT07015008

Dose–Response of Dietary Carbohydrate Intake on Skeletal Muscle Glycogen, Gastrointestinal Comfort and Body Composition in Endurance‐Trained Individuals in Simulated Preparation for Competition

Robyn O. Jones, José L. Areta, Samuel Bennett, Jamie Pugh, Julien B. Louis — Mon, 25 May 2026 08:19:42 -0700

ABSTRACT

High dietary carbohydrate (CHO) intake and reduced exercise training are recommended to optimize muscle glycogen stores pre-endurance sports competition. However, the optimal CHO intake to support muscle glycogen synthesis and the dose–response of this relationship are still unknown in athletes who continue training pre-competition. This study investigated the effects of different CHO intakes on muscle glycogen concentration. In a counterbalanced repeated measures design, 11 endurance-trained participants (3 females, 8 males; age, 24 ± 5 years; body mass, 71.2 ± 12.0 kg; V̇O_2max, 56 ± 6 mL kg⁻¹ min⁻¹) undertook 3 × 5 days of exercise and dietary control. During the final 48 h, participants ingested 6, 8 or 10 g kg⁻¹ day⁻¹ CHO prior to the assessment of muscle glycogen, gastrointestinal (GI) comfort and body composition. Muscle glycogen concentration was significantly higher following 10 vs. 6 and 8 g kg⁻¹ day⁻¹ (635.5 ± 78.0 vs. 460.9 ± 100.7 and 506.1 ± 124.0 mmol kg⁻¹ dry mass, respectively, p < 0.03), with no difference between 6 and 8 g kg⁻¹ day⁻¹ (p = 1.00). There was a strong positive correlation between relative CHO intake (r = 0.71, p < 0.001) and skeletal muscle glycogen concentration. There was no effect of CHO intake on body mass (p = 0.70) or GI symptoms (p > 0.05), except fullness. In conclusion, there was a linear dose–response between dietary CHO intake and muscle glycogen in a protocol mimicking real-world training and nutrition practices, as 10 g kg⁻¹ day⁻¹ achieved the highest muscle glycogen concentrations, with no detectable effect on body mass or GI symptoms, except increased fullness.

Dose–Response Effects of a 4‐Month FIT FIRST 10 School‐Based Multisport Programme on Physical Fitness and Psychosocial Well‐Being in Children Aged 7–11: A Three‐Arm Cluster‐Randomized Controlled Trial

Mon, 25 May 2026 08:15:28 -0700

ABSTRACT

Low physical activity (PA) and fitness in childhood are linked to adverse health outcomes, yet many Danish children do not meet national guidelines. The FIT FIRST 10 (FF10) multisport PE programme was developed to increase PA in primary schools. To evaluate dose–response effects of a 4-month FF10 intervention on physical fitness and psychosocial well-being. Three-arm, cluster-randomized trial (1:1:1). 1357 pupils (7–11 years) from 68 classes in 27 schools were allocated to control (CON, n = 529), 1.5 FF10 sessions/week (1.5INT, n = 495), or 3 FF10 sessions/week (3INT, n = 333); 1175 provided consent. The primary outcome was cardiorespiratory fitness via the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C). Secondary outcomes included cardiometabolic health, muscular fitness, and psychosocial well-being. No between-group effects were observed for the primary outcome (1.5INT vs. CON: 17 m [−19, 52]; 3INT vs. CON: −8 m [−47, 31]). Among secondary outcomes, 1.5INT showed small favorable effects on body composition (body fat percentage −0.4%; fat mass −0.2 kg; fat mass index −0.1 kg/m²; BMI −0.1 kg/m²) and handgrip strength (+0.4 kg) (all p < 0.05). No intervention effects were observed for cardiovascular or psychosocial domains. Small differences favoring CON over 3INT emerged in standing long jump (−5 cm), postural balance (−0.5 s) and perceived flexibility (−0.3 AU) (all p < 0.05). In conclusion, a moderate, feasible dose of approximately 1.5 FF10 sessions per week appeared more effective than a higher-frequency implementation, highlighting the importance of feasibility and implementation fidelity in real-world school settings. ClinicalTrials.gov (NCT06180772).

When Ventilation Fails to Reflect Disease: Obesity and the Limits of V.E‐V.CO2 Slope for Physiological and Prognostic Interpretation

Paulo de Tarso Muller — Sat, 23 May 2026 00:48:15 -0700

Scandinavian Journal of Medicine &Science in Sports, Volume 36, Issue 6, June 2026.

Issue Information

Sat, 23 May 2026 00:45:21 -0700

Scandinavian Journal of Medicine &Science in Sports, Volume 36, Issue 6, June 2026.