Yan Chen

Background/Objectives: Evidence is limited on whether carbohydrate formulations enhance resistance training adaptations when protein intake is relatively adequate. This study compared two carbohydrate–protein formulations in healthy young men. Methods: In this randomized, double-blind, placebo-controlled trial, 36 untrained men aged 18–25 years were assigned to a maltodextrin-based carbohydrate control group (PLA), low-molecular-weight carbohydrate plus protein (LMW-CHO+PRO), or high-molecular-weight carbohydrate plus protein (HMW-CHO+PRO). Thirty-three participants completed 8 weeks of supervised resistance training three times weekly and daily supplementation (50 g). Body composition, muscle circumference and thickness, strength, and serum testosterone, cortisol, and testosterone-to-cortisol ratio were assessed before and after intervention. The trial was registered with the Chinese Clinical Trial Registry (ChiCTR2500110509). Results: Body mass, total muscle mass, muscle circumference and thickness, and strength improved in all groups. Both supplementation groups showed greater improvements than PLA across several muscular adaptation measures. Time × group interactions were significant for body mass and total muscle mass, but not fat mass. HMW-CHO+PRO produced greater increases in body mass and total muscle mass than LMW-CHO+PRO; however, no consistent differences between formulations were observed in regional muscle circumference, muscle thickness, strength, or blood biomarkers. Conclusions: Under conditions of relatively adequate protein intake, combined carbohydrate and protein supplementation may provide additional support for resistance training adaptations. These findings do not establish an overall advantage of either formulation, nor can the observed differences be attributed specifically to carbohydrate molecular weight.

Background: Recreational exercise has become increasingly common among Chinese adults. However, population-specific data on sweat rate and electrolyte composition during typical daily physical activities remain limited. Therefore, this study aimed to comprehensively characterize the hydration status, sweat rate, and sweat electrolyte composition among Chinese adults engaging in common daily exercises under controlled environmental conditions, and to examine sex-related differences. Methods: In this cross-sectional study, 285 healthy adults (143 men, 142 women) were assigned to one of three separate activity groups: brisk walking (n = 100), running (n = 90), or cycling (n = 95). Activity protocols were standardized using fixed activity-specific speeds corresponding to 5.2, 8.2, and 4.4 METs for brisk walking, running, and cycling, respectively, based on the Chinese Compilation of Physical Activities. Each participant completed one 60-min exercise session under controlled environmental conditions. Sweat samples were collected from the chest using sweat patches and analyzed for Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe, Zn²⁺, and Cu²⁺ using ICP-MS/OES. Whole-body sweat sodium and potassium concentrations were estimated using validated regression equations. Body mass loss (BML) and sweat rate were calculated from pre- and post-exercise nude body mass. Results: Across all participants and activity types, the overall mean sweat rate was 0.71 ± 0.28 L/h, and the mean percentage of body mass loss (BML%) was 0.78 ± 0.45%. Among the three physical activities, running elicited higher sweat rates (0.92 ± 0.29 L/h) and BML% (1.16 ± 0.36%) than brisk walking or cycling (p < 0.05). The estimated whole-body Na⁺ and K⁺ concentrations across all participants were 34.10 ± 10.31 mmol/L and 3.35 (3.02–3.93) mmol/L, respectively, with 59.3% of participants classified as having moderate Na⁺ levels (30–60 mmol/L). Men exhibited higher sweat rates and Na⁺ concentrations, whereas women showed higher K⁺, Zn²⁺, and Cu²⁺ levels (p < 0.05). Conclusions: Chinese adults engaging in common daily physical activities under temperate environmental conditions demonstrated low-to-moderate sweat rates and sodium concentrations. These findings provide baseline reference data for population-specific hydration education and may inform future validation and application of wearable sweat-sensing technologies in public health monitoring.

Objectives: This cross-sectional study aimed to assess fluid replenishment behaviors, knowledge, and attitudes among Chinese recreational marathon runners and to inform future health education strategies regarding optimal hydration.Design: The survey was conducted between January and December 2024. Based on previously validated questionnaires, the instrument was adapted and administered to assess hydration behaviors, knowledge, and attitudes among marathon participants in major road races across China. A total of 461 valid responses were collected, including 357 male participants (38.9 ± 9.3 years) and 104 female participants (39.5 ± 8.9 years), representing a range of athletic performance levels. The response rate was 94.9%. Data were analyzed using IBM SPSS 27.0 and Microsoft Excel.Result: Over 70% of runners (72.5%) failed to meet recommended daily fluid intake standards (p < 0.001). Over half (57.7%) consumed 150 mL of fluid before the race, mainly plain water before (68.1%) and sports drinks during (56.6%) and after (54.0%) the race. Participants primarily obtained hydration knowledge from friends/family (54.9%) and social media (45.6%). Most participants (93.7%) acknowledged water’s health benefits and were willing (92.2%) to improve hydration habits to enhance athletic performance (p < 0.001 for all). Hydration knowledge varied by gender, age, and training level. Participants better understood pre- and mid-exercise hydration and the concept that thirst indicates existing dehydration. However, only 21.5% knew the recommended daily intake (1500–1700 ml), 39.9% understood the differences among mineral, spring, and purified water, and 46.8% recognized the need for post-exercise rehydration.Conclusion: These findings indicate that over half of recreational marathon runners are at risk of dehydration, highlighting that a lack of knowledge poses a dilemma for some runners who fall into a dehydrated state. This underscores the need for targeted education and awareness programs on scientific hydration knowledge and attitudes among recreational marathon runners to improve their health and athletic performance.

Purpose: Gastrointestinal (GI) symptoms are prevalent among endurance athletes, especially marathon runners, and can negatively affect performance and wellbeing. However, data on the prevalence and nutritional contributors to GI symptoms in Chinese recreational long distance runners remain limited. This study aimed to investigate the prevalence, severity, and dietary influences of GI symptoms in this population.Methodology: A total of 805 valid responses were collected through an online and offline questionnaire conducted in China between January and December 2024. Participants were recreational long distance runners recruited via running clubs, community organizations, sports associations, and online platforms. The questionnaire covered six areas: demographics, exercise habits, dietary strategies, GI symptom severity and frequency, influencing factors, and knowledge and attitudes. GI symptoms during races were assessed using the Gastrointestinal Symptom Rating Scale (GSRS), which includes 11 symptoms rated on a 7-point Likert scale.Results: Notably, 26.1% of participants reported GI symptoms during races, with bloating (18.6%), urge to defecate (17.8%), and stomach pain (16.5%) being the most frequent. Symptoms peaked in prevalence and severity during the middle phase of the race. GI symptoms were more common in males (27.9%) than females (20.8%), and runners aged 34 years and younger had a higher symptom rates. Nutritional factors, particularly pre- and mid-race dietary strategies, significantly influenced symptom occurrence. Foods high in fat, protein, fiber, or fermentable carbohydrates were commonly associated with GI distress. Eating within 30 min before a race increased the risk of bloating and urge to defecate. The use of energy gels, sports drinks, and hydration strategies also correlated with higher GI symptom risk. Other contributing factors included a history of GI issues and high monthly running volume.Discussion: The findings underscore the importance of individualized dietary planning to reduce GI symptoms among recreational long distance runners. Adjusting pre-race meal timing and avoiding certain food types may mitigate discomfort. In addition to nutrition, variables such as sex, age, training load, and medical history should be considered in preventive strategies. Future research should explore tailored nutrition and training approaches to improve athlete health and performance during endurance events.

Low energy availability (LEA) can negatively impact athletes' physiological function and performance. This study aims to examine the prevalence of LEA in Chinese female combat athletes and monitor changes in physiological function and performance during the pre-competition period. We assessed the incidence of low energy availability (LEA) and eating disorder (ED) risks in 84 female combat athletes (judo, freestyle wrestling, and sanda) from Beijing using the Low Energy Availability in Females Questionnaire (LEAF-Q) and the Eating Disorder Examination Questionnaire (EDE-Q). From this group, 11 judo athletes who were preparing for competition were selected and divided into a low energy availability (LEA) group and a non-LEA group based on their energy availability levels. Dietary intake, training energy expenditure, body composition, resting metabolic rate, blood markers, and special judo fitness tests were monitored at 4 weeks, 2 weeks, and 0 weeks before the competition. Among the 84 athletes, 45.2% of athletes (n = 38) were at increased risk of LEA, and 21.4% of athletes (n = 18) were classified as high in eating disorder risk. There were no significant differences in LEA and ED risk between elite and recreational athletes. Among the 11 athletes preparing for competition, 6 athletes (45.5%) were in a state of LEA at the initial stage (4 weeks before the competition), and by the competition week, all 11 athletes exhibited LEA. Additionally, athletes in the LEA group experienced significant reductions in VO₂ and resting metabolic rate at 0 week of the competition compared to 4 weeks prior (p < 0.05). Thyroid function indicators and IGF-1 levels of LEA group also significantly decreased (p < 0.05). After completing the four-week pre-competition weight loss, heart rate recovery during the special judo fitness test improved significantly in both the LEA and non-LEA groups (p < 0.05). The current study identified a risk of LEA among Chinese female combat sport athletes, with no significant difference in the prevalence of LEA between elite and recreational athletes. It is essential for Chinese coaches and sports medicine staff to implement LEA-related nutritional education across all performance levels. Moreover, preventive measures during training are recommended to mitigate the impact of LEA on physiological function during the pre-competition weight loss phase.

The purpose of this study is to explore the effect of carbohydrate only or carbohydrate plus protein supplementation on endurance capacity and muscle damage.Ten recreationally active male runners (...

There is increasing evidence that dietary protein intake with leucine and vitamin D is an important factor in muscle protein synthesis. This study investigated the combined effects of consuming whey protein and vitamin D₃ in the evening before bedtime or in the morning after sleeping on muscle mass and strength. Healthy, untrained males (N = 42; Age = 18–24 year) were randomly assigned into three groups: before bedtime, after sleeping, and control. Subjects underwent a 6-week resistance training program in combination with supplements that provided 25 g whey protein and 4000 IU vitamin D₃ for the before bedtime and after sleeping groups and a 5 g maltodextrin placebo for the control group. A significant increase in serum vitamin D was observed in both before bedtime and after sleeping groups. All groups experienced a significant gain in leg press. However, the control group did not experience significant improvements in muscle mass and associated blood hormones that were experienced by the before bedtime and after sleeping groups. No significant differences in assessed values were observed between the before bedtime and after sleeping groups. These findings suggest that the combination of whey protein and vitamin D supplements provided either before or after sleep resulted in beneficial increases in muscle mass in young males undergoing resistance training that exceeded the changes observed without these supplements.