Motor unit firing rates during slow and fast contractions in boys and men.

BACKGROUND: Motor unit (MU) activation during maximal contractions is lower in children compared with adults. Among adults, discrete MU activation differs, depending on the rate of contraction. We investigated the effect of contraction rate on discrete MU activation in boys and men. METHODS: Following a habituation session, 14 boys and 20 men completed two experimental sessions for knee extension and wrist flexion, in random order. Maximal voluntary isometric torque (MVIC) was determined before completing trapezoidal isometric contractions (70%MVIC) at low (10%MVIC/s) and high (35%MVIC/s) contraction rates. Surface electromyography was captured from the vastus lateralis (VL) and flexor carpi radialis (FCR) and decomposed into individual MU action potential (MUAP) trains. RESULTS: In both groups and muscles, the initial MU firing rate (MUFR) was greater (p < 0.05) at high compared with low contraction rates. The increase in initial MUFR at the fast contraction in the VL was greater in men than boys (p < 0.05). Mean MUFR was significantly lower during fast contractions only in the FCR (p < 0.05). In both groups and muscles, the rate of decay of MUFR with increasing MUAP amplitude was less steep (p < 0.05) during fast compared with slow contractions. CONCLUSION: In both groups and muscles, initial MUFRs, as well as MUFRs of large MUs were higher during fast compared with slow contractions. However, in the VL, the increase in initial MUFR was greater in men compared with boys. This suggests that in large muscles, men may rely more on increasing MUFR to generate torque at faster rates compared with boys.

Developmental changes in motor unit activity patterns: child-adult comparison using discrete motor unit analysis.

Using global surface electromyography (sEMG) and the sEMG threshold it has been suggested that children activate their type-II motor unit (MU) to a lesser extent compared with adults. However, when age-related differences in discrete MU activation are examined using sEMG decomposition this phenomenon is not observed. Furthermore, findings from these studies are inconsistent and conflicting. Therefore, the purpose of this study was to examine differences in discrete MU activation of the vastus lateralis (VL) between boys and men during moderate-intensity knee extensions. Seventeen boys and 20 men completed two laboratory sessions. Following a habituation session, maximal voluntary isometric knee extension (MVIC) torque was determined before completing trapezoidal contractions at 70% MVIC. sEMG of the VL was captured and mathematically decomposed into individual MU action potential trains. Motor unit action potential amplitude (MUAPamp), recruitment threshold (RT), and MU firing rates (MUFR) were calculated. We observed that MUAPamp-RT slope was steeper in men compared with boys (p < 0.05) even after accounting for fat thickness and quadriceps muscle depth. The mean MUFR and y-intercept of the MUFR-RT relationship were significantly (p < 0.001) lower in boys than in men. The slope of the MUFR-RT relationship tended to be steeper in men, but the differences did not reach statistical significance (p = 0.056). Overall, our results suggest that neural strategies used to produce torque are different among boys and men. Such differences may be related, in part, to boys' lower MUFR and lesser ability to activate their higher-threshold MUs. Although, other factors (e.g., muscle composition) likely also play a role.

Different discrete motor-unit activation patterns in the flexor carpi radialis in boys and men.

BACKGROUND: Lower activation of higher threshold (type-II) motor units (MUs) has been suggested in children compared with adults. We examined child-adult differences in discrete MU activation of the flexor carpi radialis (FCR). METHODS: Fifteen boys (10.2 ± 1.4 years), and 17 men (25.0 ± 2.7 years) completed 2 laboratory sessions. Following a habituation session, maximal voluntary isometric wrist flexion torque (MVIC) was determined before completing trapezoidal isometric contractions at 70%MVIC. Surface electromyography was captured by Delsys Trigno Galileo sensors and decomposed into individual MU action potential trains. Recruitment threshold (RT), and MU firing rates (MUFR) were calculated. RESULTS: MVIC was significantly greater in men (10.19 ± 1.92 Nm) than in boys (4.33 ± 1.47 Nm) (p < 0.05), but not statistically different after accounting for differences in body size. Mean MUFR was not different between boys (17.41 ± 7.83 pps) and men (17.47 ± 7.64 pps). However, the MUFR-RT slope was significantly (p < 0.05) steeper (more negative) in boys, reflecting a progressively greater decrease in MUFR with increasing RT. Additionally, boys recruited more of their MUs early in the ramped contraction. CONCLUSION: Compared with men, boys tended to recruit their MUs earlier and at a lower percentage of MVIC. This difference in MU recruitment may explain the greater decrease in MUFR with increasing RT in boys compared with men. Overall, these findings suggest an age-related difference in the neural strategy used to develop moderate-high torque in wrist flexors, where boys recruit more of their MUs earlier in the force gradation process, possibly resulting in a narrower recruitment range.

Effects of sclerostin injection on soleus and extensor digitorum longus muscle tissue in male mice.

Sclerostin, a potent inhibitor of the Wnt signaling pathway, plays a critical role in bone homeostasis. Evidence suggests that sclerostin may also be involved in crosstalk between other tissues, including muscle. This pilot study attempted to examine the effects of sclerostin on soleus and extensor digitorum longus (EDL) muscle tissue from male mice that were given continuous recombinant sclerostin injections for 4 weeks. A total of 48 10-week-old male C57BL/6J mice were assigned to be sedentary or perform 1 h treadmill running per day for 4 weeks and administered subcutaneous injections of either saline or recombinant sclerostin 5 days/week. Sclerostin injection led to a reduction in the soleus myosin heavy chain (MHC) I, MHC I/IIA, MHC IIA/X, and MHC IIB cross-sectional area (p < 0.05) with no exercise effects on these reductions. In contrast, there were no effects of sclerostin injections or exercise on the fast-twitch EDL muscle in terms of size, MHC protein, or markers of Wnt signaling. These findings provide preliminary evidence of sclerostin's endocrine role in muscle via decreases in myofiber cross-sectional area, which seems to be independent of fiber type but muscle type-specific. More studies, however, are needed to confirm these preliminary results.

Ursolic Acid against Prostate and Urogenital Cancers: A Review of In Vitro and In Vivo Studies.

Prostate cancer is the second most diagnosed form of cancer in men worldwide and accounted for roughly 1.3 million cases and 359,000 deaths globally in 2018, despite all the available treatment strategies including surgery, radiotherapy, and chemotherapy. Finding novel approaches to prevent and treat prostate and other urogenital cancers effectively is of major importance. Chemicals derived from plants, such as docetaxel and paclitaxel, have been used in cancer treatment, and in recent years, research interest has focused on finding other plant-derived chemicals that can be used in the fight against cancer. Ursolic acid, found in high concentrations in cranberries, is a pentacyclic triterpenoid compound demonstrated to have anti-inflammatory, antioxidant, and anticancer properties. In the present review, we summarize the research studies examining the effects of ursolic acid and its derivatives against prostate and other urogenital cancers. Collectively, the existing data indicate that ursolic acid inhibits human prostate, renal, bladder, and testicular cancer cell proliferation and induces apoptosis. A limited number of studies have shown significant reduction in tumor volume in animals xenografted with human prostate cancer cells and treated with ursolic acid. More animal studies and human clinical studies are required to examine the potential of ursolic acid to inhibit prostate and other urogenital cancers in vivo.

Energy Expenditure, Dietary Energy Intake, and Nutritional Supplements in Adolescent Volleyball Athletes versus Nonathletic Controls.

Evidence suggests that athletes competing in team sports do not follow dietary recommendations. However, only few studies have investigated energy needs and supplement use in adolescent athletes, and whether they are meeting their energy requirements. This observational study examined energy expenditure, dietary energy intake, and use of nutritional supplements in 58 adolescent (14-17 years old) volleyball athletes (15 males, 43 females) and 58 age-matched nonathletic controls (13 males, 45 females). Participants completed an online survey including questions on demographic information, body mass, and a series of standardized questionnaires assessing energy expenditure, dietary energy, macronutrient, micronutrient, and supplement intake. Energy expenditure relative to body mass was higher in athletes than nonathletes by 13 kcal/kg/day (group effect, p < 0.001), and in males compared to females by 5.7 kcal/kg/day (sex effect, p = 0.004). Athletes had higher energy intake than nonathletes (+6.4 kcal/kg/day, p = 0.019) and greater consumption of fruits (p = 0.034), vegetables (p = 0.047), grains (p = 0.016), dairy (p = 0.038), meats and meat alternatives (p < 0.001), as well as higher intakes of fat (p < 0.001), carbohydrates, protein, sugar, fiber, vitamin C, calcium, and sodium (p = 0.05) compared to nonathletes. The average protein intakes exceeded the upper recommendations in all groups, suggesting that this is not a nutrient of concern for young volleyball athletes. However, athletes were only meeting 60% of the estimated energy requirements (EER) for their age, height, body mass, and physical activity score, (3322 ± 520 kcal/day), while nonathletes were meeting 74% of the EER (p < 0.001). The relative energy balance of male athletes was lower compared to both female athletes (p = 0.006) and male nonathletes (p = 0.004). Finally, more athletes reported using performance-related supplements than nonathletes, but there were no differences in the consumption of other dietary supplements. Overall, when compared to nonathletic controls, both male and female adolescent volleyball athletes were found to match their higher energy expenditure with a greater dietary energy intake; however, all adolescents were below the estimated energy requirements, a finding more profound among the volleyball athletes.

Trio RNA sequencing in a cohort of medically complex children.

Genome sequencing (GS) is a powerful test for the diagnosis of rare genetic disorders. Although GS can enumerate most non-coding variation, determining which non-coding variants are disease-causing is challenging. RNA sequencing (RNA-seq) has emerged as an important tool to help address this issue, but its diagnostic utility remains understudied, and the added value of a trio design is unknown. We performed GS plus RNA-seq from blood using an automated clinical-grade high-throughput platform on 97 individuals from 39 families where the proband was a child with unexplained medical complexity. RNA-seq was an effective adjunct test when paired with GS. It enabled clarification of putative splice variants in three families, but it did not reveal variants not already identified by GS analysis. Trio RNA-seq decreased the number of candidates requiring manual review when filtering for de novo dominant disease-causing variants, allowing for the exclusion of 16% of gene-expression outliers and 27% of allele-specific-expression outliers. However, clear diagnostic benefit from the trio design was not observed. Blood-based RNA-seq can facilitate genome analysis in children with suspected undiagnosed genetic disease. In contrast to DNA sequencing, the clinical advantages of a trio RNA-seq design may be more limited.

Changes in Body Mass, Physical Activity, and Dietary Intake during the COVID-19 Pandemic Lockdowns in Canadian University Students.

This study examined changes in body mass and body mass index (BMI), physical activity, and dietary intake in Canadian university students during the first year of the COVID-19 pandemic. Two self-reported recall surveys were conducted: after the first lockdown in September 2020 (T1) and following the second lockdown in March 2021 (T2). Eligible participants were full-time undergraduate students attending a Canadian university and residing in Canada during the first year of the pandemic. At T1, 510 students (99 male, 411 female) completed the survey, and of those, 135 (32 males, 103 females) completed the survey at T2 (73% attrition). At both T1 and T2, most participants were 18-24 years of age (93% and 90%, respectively), Caucasian (73% and 78%, respectively), and resided in the province of Ontario (79% and 80%, respectively). Body mass increased from T1 to T2 (+0.91 ± 3.89 kg t(132) = -2.7, p = 0.008). BMI also increased from T1 to T2 (+0.30 ± 1.33 kg/m2 [t(130) = -2.5, p = 0.012), with a greater number of participants within the overweight range (19.8% versus 24.4%, respectively). At T1, 38% of the participants reported a decrease in physical activity, while the number of students reporting a decrease in activity increased to 56% at T2. Dietary energy intake decreased from 1678 ± 958 kcal/day at T1 to 1565 ± 842 kcal/day at T2 [c2(1) = 7.2, p = 0.007]. Diet quality also decreased, with participants not meeting the recommended daily allowance for essential macro and micronutrients. A decrease was observed in daily servings of fruits (-27%, p < 0.001), vegetables (-72%, p < 0.001), and grains (-68%, p < 0.001). In conclusion, despite a small decrease in dietary energy intake, a modest weight gain occurred during the first year of the COVID-19 pandemic in this cohort of Canadian university students, which was potentially related to decreased physical activity and diet quality.

Sclerostin Influences Exercise-Induced Adaptations in Body Composition and White Adipose Tissue Morphology in Male Mice.

Sclerostin is an inhibitor of the osteogenic Wnt/ß-catenin signaling pathway that also has an endocrine role in regulating adipocyte differentiation and metabolism. Additionally, subcutaneous white adipose tissue (scWAT) sclerostin content decreases following exercise training (EXT). Therefore, we hypothesized that EXT-induced reductions in adipose tissue sclerostin may play a role in regulating adaptations in body composition and whole-body metabolism. To test this hypothesis, 10-week-old male C57BL/6J mice were either sedentary (SED) or performing 1 hour of treadmill running at ~65% to 70% maximum oxygen consumption (VO2max ) 5 day/week (EXT) for 4 weeks and had subcutaneous injections of either saline (C) or recombinant sclerostin (S) (0.1 mg/kg body mass) 5 day/week; thus, making four groups (SED-C, EXT-C, SED-S, and EXT-S; n = 12/group). No differences in body mass were observed between experimental groups, whereas food intake was higher in EXT (p = 0.03) and S (p = 0.08) groups. There was a higher resting energy expenditure in all groups compared to SED-C. EXT-C had increased lean mass and decreased fat mass percentage compared to SED-C and SED-S. No differences in body composition were observed in either the SED-S or EXT-S groups. Lower scWAT (inguinal), epididymal white adipose tissue (eWAT) (visceral epididymal) mass, and scWAT adipocyte cell size and increased percentage of multilocular cells in scWAT were observed in the EXT-C group compared to SED-C, whereas lower eWAT was only observed in the EXT-S group. EXT mice had increased scWAT low-density lipoprotein receptor-related protein 4 (Lrp4) and mitochondrial content and sclerostin treatment only inhibited increased Lrp4 content with EXT. Together, these results provide evidence that reductions in resting sclerostin with exercise training may influence associated alterations in energy metabolism and body composition, particularly in scWAT. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Correction: Klentrou et al. Circulating Levels of Bone Markers after Short-Term Intense Training with Increased Dairy Consumption in Adolescent Female Athletes. Children 2021, 8, 961.

There was an error in the original publication [...].

Beyond its Psychiatric Use: The Benefits of Low-dose Lithium Supplementation.

Lithium is most well-known for its mood-stabilizing effects in the treatment of bipolar disorder. Due to its narrow therapeutic window (0.5-1.2 mM serum concentration), there is a stigma associated with lithium treatment and the adverse effects that can occur at therapeutic doses. However, several studies have indicated that doses of lithium under the predetermined therapeutic dose used in bipolar disorder treatment may have beneficial effects not only in the brain but across the body. Currently, literature shows that low-dose lithium (≤0.5 mM) may be beneficial for cardiovascular, musculoskeletal, metabolic, and cognitive function, as well as inflammatory and antioxidant processes of the aging body. There is also some evidence of low-dose lithium exerting a similar and sometimes synergistic effect on these systems. This review summarizes these findings with a focus on low-dose lithium's potential benefits on the aging process and age-related diseases of these systems, such as cardiovascular disease, osteoporosis, sarcopenia, obesity and type 2 diabetes, Alzheimer's disease, and the chronic low-grade inflammatory state known as inflammaging. Although lithium's actions have been widely studied in the brain, the study of the potential benefits of lithium, particularly at a low dose, is still relatively novel. Therefore, this review aims to provide possible mechanistic insights for future research in this field.

Bone Turnover Markers and Osteokines in Adolescent Female Athletes of High- and Low-Impact Sports Compared With Nonathletic Controls.

This study examined differences in resting concentrations of markers of bone formation and resorption, and osteokines between female adolescent (12-16 y) swimmers, soccer players, and nonathletic controls. Resting, morning blood samples were obtained after an overnight fast from 20 swimmers, 20 soccer players, and 20 nonathletic controls, matched for age. carboxyl-terminal cross-linking telopeptide of type I collagen (CTX), amino-terminal propeptide of type I collagen (P1NP), total osteocalcin (OC), sclerostin, osteoprotegerin (OPG), and receptor activator of nuclear factor kappa B ligand (RANKL) were analyzed in serum. After controlling for percent body fat, there were no significant differences between swimmers and nonathletic controls in any of the measured markers. In contrast, soccer players had significantly higher P1NP (89.5 [25.6] ng·mL-1), OC (57.6 [22.9] ng·mL-1), and OPG (1052.5 [612.6] pg·mL-1) compared with both swimmers (P1NP: 66.5 [20.9] ng·mL-1; OC: 24.9 [12.5] ng·mL-1; OPG: 275.2 [83.8] pg·mL-1) and controls (P1NP: 58.5 [16.2] ng·mL-1; OC: 23.2 [11.9] ng·mL-1; OPG: 265.4 [97.6] pg·mL-1), with no differences in CTX, sclerostin, and RANKL. These results suggest that bone formation is higher in adolescent females engaged in high-impact sports like soccer compared with swimmers and controls.

Lipopolysaccharide-Induced Bone Loss in Rodent Models: A Systematic Review and Meta-Analysis.

Osteoporosis has traditionally been characterized by underlying endocrine mechanisms, though evidence indicates a role of inflammation in its pathophysiology. Lipopolysaccharide (LPS), a component of gram-negative bacteria that reside in the intestines, can be released into circulation and stimulate the immune system, upregulating bone resorption. Exogenous LPS is used in rodent models to study the effect of systemic inflammation on bone, and to date a variety of different doses, routes, and durations of LPS administration have been used. The study objective was to determine whether systemic administration of LPS induced inflammatory bone loss in rodent models. A systematic search of Medline and four other databases resulted in a total of 110 studies that met the inclusion criteria. Pooled standardized mean differences (SMDs) and corresponding 95% confidence intervals (CI) with a random-effects meta-analyses were used for bone volume fraction (BV/TV) and volumetric bone mineral density (vBMD). Heterogeneity was quantified using the I2 statistic. Shorter-term (<2 weeks) and longer-term (>2 weeks) LPS interventions were analyzed separately because of intractable study design differences. BV/TV was significantly reduced in both shorter-term (SMD = -3.79%, 95% CI [-4.20, -3.38], I2 62%; p < 0.01) and longer-term (SMD = -1.50%, 95% CI [-2.00, -1.00], I2 78%; p < 0.01) studies. vBMD was also reduced in both shorter-term (SMD = -3.11%, 95% CI [-3.78, -2.44]; I2 72%; p < 0.01) and longer-term (SMD = -3.49%, 95% CI [-4.94, -2.04], I2 82%; p < 0.01) studies. In both groups, regardless of duration, LPS negatively impacted trabecular bone structure but not cortical bone structure, and an upregulation in bone resorption demonstrated by bone cell staining and serum biomarkers was reported. This suggests systemically delivered exogenous LPS in rodents is a viable model for studying inflammatory bone loss, particularly in trabecular bone. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Correction: McKinlay et al. Effects of Post-Exercise Whey Protein Consumption on Recovery Indices in Adolescent Swimmers. Int. J. Environ. Res. Public Health 2020, 17, 7761.

The authors of "Effects of Post-Exercise Whey Protein Consumption on Recovery Indices in Adolescent Swimmers" report an error in Table 1 of their article [...].

The Influence of Increased Dairy Product Consumption, as Part of a Lifestyle Modification Intervention, on Diet Quality and Eating Patterns in Female Adolescents with Overweight/Obesity.

Our study examined how increased dairy consumption versus habitually low dairy consumption, against a background of healthy eating (and exercise), influenced diet quality, nutrient intake, and snacking in Canadian female adolescents (14.8 ± 2.2 years) with overweight/obesity (OW/OB). We also explored dairy consumption patterns in the group consuming dairy products. Participants were randomized into two groups: higher/recommended dairy (RDa; 4 svg/d; n = 24) or low dairy (LDa; 0−2 svg/d; n = 23). Both groups participated in a 12-week, eucaloric, lifestyle modification intervention consisting of exercise training and nutritional counseling. The intervention increased the total Canadian Healthy Eating Index score (p < 0.001) with no differences between groups. The "other food" sub-score improved more in RDa than LDa (p = 0.02), and the "saturated fat" sub-score increased more in LDa than RDa (p = 0.02). The intervention significantly increased the consumption of dairy-related nutrients more in RDa than LDa (p < 0.05). The intervention also decreased snack size in both groups (p = 0.01) and improved percentage of healthy snack energy intake more in RDa than LDa (p = 0.04). More servings of dairy products were consumed as snacks than at breakfast, lunch, or dinner (p < 0.05). Thus, our study improved diet quality, and dairy product consumption improved intakes of key related nutrients and snack consumption in adolescents with OW/OB.

Acute Effects of Milk vs. Carbohydrate on Bone Turnover Biomarkers Following Loading Exercise in Young Adult Females.

Dairy products and impact exercise have previously been identified to be independently beneficial for bone mineral properties, however, it is unknown how the combination of these two osteogenic interventions may alter acute bone turnover. Using a randomized crossover design, we compared the acute effects of consuming milk vs. an isoenergetic carbohydrate control beverage on bone biomarkers following loading exercise. Thirteen healthy female participants (Age = 20.3 ± 2.3y; BMI = 21.0 ± 1.1 kg/m2) consumed either 550 mL of 0% skim white milk (MILK) or 52.7 g of maltodextrin in 550 mL of water (CHO), both 5 min and 1 h following completion of a combined plyometric (198 impacts) and resistance exercise (3-4 sets/exercise, 8-12 reps/set, ∼75% 1-RM) bout. Venous blood samples were obtained pre-exercise, and 15 min, 75 min, 24 h and 48 h post-exercise to assess serum concentrations of bone resorption biomarkers, specifically carboxyl-terminal crosslinking telopeptide of type I collagen (CTX), receptor activator nuclear factor kappa-ß ligand (RANKL), and sclerostin (SOST), as well as bone formation biomarkers, specifically osteoprotegerin (OPG) and osteocalcin (OC). When absolute biomarker concentrations were examined, there were no interaction or group effects for any biomarker, however, there were main time effects (p < 0.05) for RANKL, SOST, and OC, which were lower, and the OPG: OPG/RANKL ratio, which was higher at 75 min post-exercise compared with baseline in both conditions. In addition to assessing absolute biomarker concentrations at specific timepoints, we also evaluated the relative (% change) cumulative post-exercise response (75 min to 48 h) using an area under the curve (AUC) analysis. This analysis showed that the relative post-exercise CTX response was significantly lower in the MILK compared to the CHO condition (p = 0.03), with no differences observed in the other biomarkers. These results show that while milk does not appear to alter absolute concentrations of bone biomarkers compared to CHO, it may attenuate relative post-exercise bone resorption (i.e., blunt the usual catabolic response to exercise).

Intensified training in adolescent female athletes: a crossover study of Greek yogurt effects on indices of recovery.

Background: During a period of intensified exercise (e.g. training/identification camps), often undertaken by competitive youth athletes, the maintenance of muscle function and peak performance can become challenging due to an accumulation of fatigue. The provision of post-exercise dairy protein in adults has been previously shown to accelerate recovery; however, its efficacy in youth athletes is currently unknown. Therefore, the purpose of this study was to examine the effects of increased dairy protein consumption with plain Greek yogurt (GY) on performance and recovery indices during an intensified soccer training camp in adolescent female soccer players. Methods: Thirteen players (14.3 ± 1.3 years) participated in a randomized, double blinded, crossover design study where they received 3 servings/day of either GY (~115 kcal, 17 g protein, ~11.5 g carbohydrates) or an isoenergetic carbohydrate control (CHO, ~115 kcal, 0.04 g protein, ~28.6 g carbohydrates) during two 5-day soccer-specific training camps. Performance was assessed before and after each training camp. Fasted, morning, creatine kinase (CK), insulin-like growth factor-1 (IGF-1), C-reactive protein (CRP), interleukin 6 (IL6), interleukin 10 (IL10) and tumor necrosis factor-α (TNFα) were measured in plasma pre- and post-training. Results: Training led to decrements in counter-movement jump (p = 0.01), broad jump (p = 0.04) and aerobic capacity (p = 0.006), with no effect of GY. A significant increase in anti-inflammatory cytokine IL10 was observed from pre- to post-training in GY (+26% [p = 0.008]) but not in CHO (p = 0.89). CRP and CK increased (+65% [p = 0.005] and +119% [p ≤ 0.001], respectively), while IGF-1 decreased (-34% [p ≤ 0.001]) from pre- to post-training with no difference between conditions. Conclusions: These results demonstrate that consumption of GY did not offer any added recovery benefit with respect to measures of performance and in the attenuation of exercise-induced muscle damage above that achieved with energy-matched carbohydrate in this group of young female soccer players. However, regular consumption of GY may assist with the acute anti-inflammatory response during periods of intensified training in adolescent athletes.

Menstrual Cycle Related Fluctuations in Circulating Markers of Bone Metabolism at Rest and in Response to Running in Eumenorrheic Females.

This study examined potential fluctuations in bone metabolic markers across the menstrual cycle both at rest and after a 30-min bout of continuous running at 80% of V̇O2max. Resting and post-exercise (0, 30, 90 min) sclerostin, parathyroid hormone (PTH), carboxy-terminal cross-linking telopeptide of type I collagen (ß-CTXI), and procollagen type 1 N propeptide (PINP) were assessed in 10 eumenorrheic women (age: 21 ± 3 y, BMI: 23.2 ± 3.0 kg.m2) during the mid- to late-follicular (FP: day 8.0 ± 1.4) and mid-luteal (LP: day 22.0 ± 2.5) phases of the menstrual cycle. Ovulation was determined using ovulation kits and daily measurement of oral body temperature upon awakening. Menstrual cycle phase was subsequently confirmed by measurement of plasma estradiol and progesterone. On average, resting estradiol concentrations increased from 46.3 ± 8.9 pg·mL-1 in the FP to 67.3 ± 23.4 pg·mL-1 in the LP (p = 0.015), and resting progesterone increased from 4.12 ± 2.36 ng·mL-1 in the FP to 11.86 ± 4.49 ng·mL-1 in the LP (p < 0.001). At rest, there were no differences between menstrual cycle phases in sclerostin (FP: 260.1 ± 135.0 pg·mL-1; LP: 303.5 ± 99.9 pg·mL-1; p = 0.765), PTH (FP: 0.96 ± 0.64 pmol·L-1; LP: 0.79 ± 0.44 pmol·L-1; p = 0.568), ß-CTXI (FP: 243.1 ± 158.0 ng·L-1; LP: 202.4 ± 92.3 ng·L-1; p = 0.198), and PINP (FP: 53.6 ± 8.9 µg·L-1; LP: 66.2 ± 20.2 µg·L-1; p = 0.093). Main effects for time (p < 0.05) were shown in sclerostin, PTH, ß-CTXI and PINP, without phase or interaction effects. Sclerostin increased from pre- to immediately post-exercise (45%; p = 0.007), and so did PTH (43%; p = 0.011), both returning to resting concentrations 30 min post-exercise. ß-CTXI decreased from pre- to post-exercise (20%; p = 0.027) and was still below its pre-exercise concentrations at 90 min post-exercise (17%; p = 0.013). PINP increased immediately post-exercise (29%; p < 0.001), returning to resting concentrations at 30 min post-exercise. These results demonstrate no effect of menstrual cycle phase on resting bone marker concentrations or on the bone metabolic marker response to intense exercise.

Subcutaneous adipose tissue sclerostin is reduced and Wnt signaling is enhanced following 4-weeks of sprint interval training in young men with obesity.

Sclerostin is a Wnt/ß-catenin antagonist, mainly secreted by osteocytes, and most known for its role in reducing bone formation. Studies in rodents suggest sclerostin can also regulate adipose tissue mass and metabolism, representing bone-adipose tissue crosstalk. Exercise training has been shown to reduce plasma sclerostin levels; but the effects of exercise on sclerostin and Wnt/ß-catenin signaling specifically within adipose tissue has yet to be examined. The purpose of this study was to examine subcutaneous WAT (scWAT) sclerostin content and Wnt signaling in response to exercise training in young men with obesity. To this end, 7 male participants (BMI = 35 ± 4; 25 ± 4 years) underwent 4 weeks of sprint interval training (SIT) involving 4 weekly sessions consisting of a 5-min warmup, followed by 8 × 20 s intervals at 170% of work rate at VO2peak , separated by 10 s of rest. Serum and scWAT were sampled at rest both pre- and post-SIT. Despite no changes in serum sclerostin levels, we found a significant decrease in adipose sclerostin content (-37%, p = 0.04), an increase in total ß-catenin (+52%, p = 0.03), and no changes in GSK3ß serine 9 phosphorylation. There were also concomitant reductions in serum TNF-α (-0.36 pg/ml, p = 0.03) and IL-6 (-1.44 pg/ml, p = 0.05) as well as an increase in VO2peak (+5%, p = 0.03) and scWAT COXIV protein content (+95%, p = 0.04). In conclusion, scWAT sclerostin content was reduced and ß-catenin content was increased following SIT in young men with excess adiposity, suggesting a role of sclerostin in regulating human adipose tissue in response to exercise training.

Postexercise serum from humans influences the biological tug of war of APP processing in human neuronal cells.

Neurodegenerative diseases such as Alzheimer's disease (AD) are becoming more prevalent in our aging society. One specific neuropathological hallmark of this disease is the accumulation of amyloid-ß (Aß) peptides, which aggregate to form extraneuronal plaques. Increased Aß peptides are often observed well before symptoms of AD develop, highlighting the importance of targeting Aß-producing pathways early on in disease progression. Evidence indicates that exercise has the capacity to reduce Aß peptide production in the brain; however, the mechanisms remain unknown. Exercise-induced signaling mediators could be the driving force behind some of the beneficial effects observed in the brain with exercise. The purpose of this study was to examine if postexercise serum and the factors it contains can alter neuronal amyloid precursor protein (APP) processing. Human SH-SY5Y neuronal cells were differentiated with retinoic acid for 5 days and treated with 10% pre- or postexercise serum from humans for 30 min. Cells were collected for analysis of acute (30 min; n = 6) or adaptive (24 h posttreatment; n = 6) responses. There were no statistical differences in a disintegrin and metalloproteinase 10 (ADAM10) and ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) mRNA or protein expression with postexercise serum treatment at either time point. However, there was an increase in the ratio of soluble amyloid precursor protein α (sAPPα) to soluble amyloid precursor protein ß (sAPPß) protein content (P = 0.05) after 30 min of postexercise serum treatment. In addition, 30 min of postexercise serum treatment increased ADAM10 (P = 0.01) and BACE1 (P = 0.02) activity. These findings suggest that postexercise serum modulates important enzymes involved in APP processing, potentially pushing the cascade toward the nonamyloidogenic arm.