The IFITM5 mutation in osteogenesis imperfecta type V is associated with an ERK/SOX9-dependent osteoprogenitor differentiation defect.

Osteogenesis imperfecta (OI) type V is the second most common form of OI, distinguished by hyperplastic callus formation and calcification of the interosseous membranes in addition to bone fragility. It is caused by a recurrent, dominant pathogenic variant (c.-14C>T) in IFITM5. Here, we generated a conditional Rosa26 knock-in mouse model to study the mechanistic consequences of the recurrent mutation. Expression of the mutant Ifitm5 in osteo-chondroprogenitor or chondrogenic cells resulted in low bone mass and growth retardation. Mutant limbs showed impaired endochondral ossification, cartilage overgrowth, and abnormal growth plate architecture. The cartilage phenotype correlates with the pathology reported in OI type V patients. Surprisingly, expression of mutant Ifitm5 in mature osteoblasts caused no obvious skeletal abnormalities. In contrast, earlier expression in osteo-chondroprogenitors was associated with increase in the skeletal progenitor population within the periosteum. Lineage tracing showed that chondrogenic cells expressing the mutant Ifitm5 showed decreased differentiation into osteoblastic cells in diaphyseal bone. Moreover, mutant IFITM5 disrupts early skeletal homeostasis in part by activating ERK signaling and downstream SOX9 protein, and inhibition of these pathways partially rescued the phenotype in mutant animals. These data identify the contribution of a signaling defect altering osteo-chondroprogenitor differentiation as a driver in the pathogenesis of OI type V.

The Gut Microbiome Controls Liver Tumors via the Vagus Nerve.

Liver cancer ranks amongst the deadliest cancers. Nerves have emerged as an understudied regulator of tumor progression. The parasympathetic vagus nerve influences systemic immunity via acetylcholine (ACh). Whether cholinergic neuroimmune interactions influence hepatocellular carcinoma (HCC) remains uncertain. Liver denervation via hepatic vagotomy (HV) significantly reduced liver tumor burden, while pharmacological enhancement of parasympathetic tone promoted tumor growth. Cholinergic disruption in Rag1KO mice revealed that cholinergic regulation requires adaptive immunity. Further scRNA-seq and in vitro studies indicated that vagal ACh dampens CD8+ T cell activity via muscarinic ACh receptor (AChR) CHRM3. Depletion of CD8+ T cells abrogated HV outcomes and selective deletion of Chrm3 on CD8 + T cells inhibited liver tumor growth. Beyond tumor-specific outcomes, vagotomy improved cancer-associated fatigue and anxiety-like behavior. As microbiota transplantation from HCC donors was sufficient to impair behavior, we investigated putative microbiota-neuroimmune crosstalk. Tumor, rather than vagotomy, robustly altered fecal bacterial composition, increasing Desulfovibrionales and Clostridial taxa. Strikingly, in tumor-free mice, vagotomy permitted HCC-associated microbiota to activate hepatic CD8+ T cells. These findings reveal that gut bacteria influence behavior and liver anti-tumor immunity via a dynamic and pharmaceutically targetable, vagus-liver axis.

Delayed skeletal development and IGF-1 deficiency in a mouse model of lysinuric protein intolerance.

SLC7A7 deficiency, or lysinuric protein intolerance (LPI), causes loss of function of the y+LAT1 transporter critical for efflux of arginine, lysine and ornithine in certain cells. LPI is characterized by urea cycle dysfunction, renal disease, immune dysregulation, growth failure, delayed bone age and osteoporosis. We previously reported that Slc7a7 knockout mice (C57BL/6×129/SvEv F2) recapitulate LPI phenotypes, including growth failure. Our main objective in this study was to characterize the skeletal phenotype in these mice. Compared to wild-type littermates, juvenile Slc7a7 knockout mice demonstrated 70% lower body weights, 87% lower plasma IGF-1 concentrations and delayed skeletal development. Because poor survival prevents evaluation of mature knockout mice, we generated a conditional Slc7a7 deletion in mature osteoblasts or mesenchymal cells of the osteo-chondroprogenitor lineage, but no differences in bone architecture were observed. Overall, global Slc7a7 deficiency caused growth failure with low plasma IGF-1 concentrations and delayed skeletal development, but Slc7a7 deficiency in the osteoblastic lineage was not a major contributor to these phenotypes. Future studies utilizing additional tissue-specific Slc7a7 knockout models may help dissect cell-autonomous and non-cell-autonomous mechanisms underlying phenotypes in LPI.

Repeated-sprint training in heat and hypoxia: Acute responses to manipulating exercise-to-rest ratio.

The aim of this study was to investigate acute performance and physiological responses to the manipulation of exercise-to-rest ratio (E:R) during repeated-sprint hypoxic training (RSH) in hot conditions. Twelve male team-sport players completed two experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144), air temperature of 40°C and relative humidity of 50%. Exercise involved either 3 × 5 × 10-s (E:R1:2) or 3 × 10 × 5-s (E:R1:4) maximal cycling sprints interspersed with active recoveries at 120W (20-s between sprints, 2.5 and 5-min between sets for E:R1:2 and E:R1:4 respectively). Sessions were matched for overall sprint and total session duration (47.5-min). Peak and mean power output, and total work were greater in E:R1:4 than E:R1:2 (p < 0.05). Peak core temperature was significantly higher in E:R1:4 than E:R1:2 (38.44 ± 0.33 vs. 38.20 ± 0.35°C, p = 0.028). Muscle deoxygenation magnitude during sprints was greater in E:R1:2 (28.2 ± 1.6 vs. 22.4 ± 4.6%, p < 0.001), while muscle reoxygenation did not differ between conditions (p > 0.05). These results indicate E:R1:4 increased mechanical power output and core temperature compared to E:R1:2. Both protocols had different effects on measures of muscle oxygenation, with E:R1:2 generating greater muscle oxygen extraction and E:R1:4 producing more muscle oxygenation flux, which are both important signals for peripheral adaptation. We conclude that the E:R manipulation during RSH in the heat might be used to target different physiological and performance outcomes, with these findings forming a strong base for future mechanistic investigation.Highlights During a typical repeated-sprint training session conducted in hot and hypoxic conditions, an exercise-to-rest ratio of 1:4 during sprint efforts displayed an increased mechanical power output compared to an exercise-to-rest ratio of 1:2. This represents a potentially useful increase in training stimulus.An exercise-to-rest ratio of 1:2 generated greater muscle oxygen extraction, while an exercise-to-rest ratio of 1:4 resulted in more muscle oxygenation flux and a higher core temperature, indicating key markers of environment-related physiological strain were varied between conditions.Exercise-to-rest ratio manipulation may be used to target different physiological and performance outcomes when prescribing repeated-sprint training in hot and hypoxic conditions.

Increased air temperature during repeated-sprint training in hypoxia amplifies changes in muscle oxygenation without decreasing cycling performance.

The present study aims to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during repeated-sprint training in hypoxia (RSH). Thirteen male team-sport players completed one familiarisation and three experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144). Air temperatures utilised across the three experimental sessions were: 20°C, 35°C and 40°C (all 50% relative humidity). Participants performed 3 × 5 × 10-s maximal cycle sprints, with 20-s passive recovery between sprints, and 5 min active recovery between sets. There were no differences between conditions for cycling peak power, mean power, and total work (p>0.05). Peak core temperature (Tc) was not different between conditions (38.11 ± 0.36°C). Vastus lateralis muscle deoxygenation during exercise and reoxygenation during recovery was of greater magnitude in 35°C and 40°C than 20°C (p<0.001 for all). There was no condition × time interaction for Tc, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion and thermal sensation (P>0.05). Exercise-induced increases in blood lactate concentration were higher in 35°C and 40°C than 20°C (p=0.010 and p=0.001, respectively). Integrating ambient temperatures up to 40°C into a typical RSH session had no detrimental effect on performance. Additionally, the augmented muscle oxygenation changes experienced during exercise and recovery in temperatures ≥35°C may indicate that the potency of RSH training is increased with additional heat. However, alterations to the training session may be required to generate a sufficient rise in Tc for heat training purposes.Highlights Heat exposure (35-40°C) did not affect mechanical performance during a typical RSH session. This indicates hot ambient temperature can be implemented during RSH, without negative consequence to training output.Hotter ambient conditions (35-40°C) likely result in greater muscle oxygenation changes during both exercise and recovery compared to temperate conditions.Although hotter sessions were perceived as more difficult and more thermally challenging, they did not further elevate Tc beyond that of temperate conditions. Accordingly, if intended to be used for heat acclimation purposes, alterations to the session may be required to increase heat load.

Taking the plunge: When is best for hot water immersion to complement exercise in heat and hypoxia.

This investigation assessed the psycho-physiological and performance effects of hot water immersion (HWI) implemented either before or after a repeated-sprint training in hypoxia (RSH) session conducted in the heat. Ten participants completed three RSH trials (3 × 10 × 5-s sprints), conducted at 40°C and simulated altitude of 3000 m. A 30-min monitoring period preceded and followed all exercise sessions. In PRE, the pre-exercise period was HWI, and the post-exercise period was seated rest in temperate conditions. This combination was reversed in POST. In CON, participants were seated in temperate conditions for both periods. Compared to CON, PRE elicited a reduction in power output during each repeated-sprint set (14.8-16.2%, all p < 0.001), and a significantly higher core temperature (Tc) during the pre-exercise period and throughout the exercise session (p < 0.001 and p = 0.025, respectively). In POST, power output and Tc until the end of exercise were similar to CON, with Tc higher at the conclusion of the post-exercise period (p < 0.001). Time across the entire protocol spent ≥38.5°C Tc was significantly longer in PRE (48.1 ± 22.5 min) than POST (31.0 ± 11.3 min, p = 0.05) and CON (15.8 ± 16.3 min, p < 0.001). Employing HWI following RSH conducted in the heat provides effective outcomes regarding physiological strain and cycling performance when compared to pre-exercise or no HWI.

Yap and Taz promote osteogenesis and prevent chondrogenesis in neural crest cells in vitro and in vivo.

Neural crest cells (NCCs) are multipotent stem cells that can differentiate into multiple cell types, including the osteoblasts and chondrocytes, and constitute most of the craniofacial skeleton. Here, we show through in vitro and in vivo studies that the transcriptional regulators Yap and Taz have redundant functions as key determinants of the specification and differentiation of NCCs into osteoblasts or chondrocytes. Primary and cultured NCCs deficient in Yap and Taz switched from osteogenesis to chondrogenesis, and NCC-specific deficiency for Yap and Taz resulted in bone loss and ectopic cartilage in mice. Yap bound to the regulatory elements of key genes that govern osteogenesis and chondrogenesis in NCCs and directly regulated the expression of these genes, some of which also contained binding sites for the TCF/LEF transcription factors that interact with the Wnt effector ß-catenin. During differentiation of NCCs in vitro and NCC-derived osteogenesis in vivo, Yap and Taz promoted the expression of osteogenic genes such as Runx2 and Sp7 but repressed the expression of chondrogenic genes such as Sox9 and Col2a1. Furthermore, Yap and Taz interacted with ß-catenin in NCCs to coordinately promote osteoblast differentiation and repress chondrogenesis. Together, our data indicate that Yap and Taz promote osteogenesis in NCCs and prevent chondrogenesis, partly through interactions with the Wnt-ß-catenin pathway.

DDRGK1 is required for the proper development and maintenance of the growth plate cartilage.

Loss-of-function mutations in DDRGK1 have been shown to cause Shohat type spondyloepimetaphyseal dysplasia (SEMD). In zebrafish, loss of function of ddrgk1 leads to defects in early cartilage development. Ddrgk1-/- mice show delayed mesenchymal condensation in the limb buds and early embryonic lethality. Mechanistically, Ddrgk1 interacts with Sox9 and reduces ubiquitin-mediated proteasomal degradation of Sox9 protein. To investigate the cartilage-specific role of DDRGK1, conditional knockout mice were generated by intercrossing Prx1-Cre transgenic mice with Ddrgkfl/fl mice to delete its expression in limb mesenchymal cells. Mutant mice showed progressive severe shortening of the limbs and joint abnormalities. The growth plate showed disorganization with shortened proliferative zone and enlarged hypertrophic zone. In correlation with these findings, Sox9 and Col2a1 protein levels were decreased, while Col10a1 expression was expanded. These data demonstrate the importance of Ddrgk1 during growth plate development. In contrast, deletion of Ddrgk1 with the osteoblast-specific Osteocalcin-Cre and Leptin receptor-Cre lines did not show bone phenotypes, suggesting that the effect on limb development is cartilage-specific. To evaluate the role of DDRGK1 in cartilage postnatal homeostasis, inducible Agc1-CreERT2; Ddrgklfl/fl mice were generated. Mice in which Ddrgk1 was deleted at 3 months of age showed disorganized growth plate, with significant reduction in proteoglycan deposition. These data demonstrate a postnatal requirement for Ddrgk1 in maintaining normal growth plate morphology. Together, these findings highlight the physiological role of Ddrgk1 in the development and maintenance of the growth plate cartilage. Furthermore, these genetic mouse models recapitulate the clinical phenotype of short stature and joint abnormalities observed in patients with Shohat type SEMD.

4-PBA Treatment Improves Bone Phenotypes in the Aga2 Mouse Model of Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a genetically heterogenous disorder most often due to heterozygosity for mutations in the type I procollagen genes, COL1A1 or COL1A2. The disorder is characterized by bone fragility leading to increased fracture incidence and long-bone deformities. Although multiple mechanisms underlie OI, endoplasmic reticulum (ER) stress as a cellular response to defective collagen trafficking is emerging as a contributor to OI pathogenesis. Herein, we used 4-phenylbutiric acid (4-PBA), an established chemical chaperone, to determine if treatment of Aga2+/- mice, a model for moderately severe OI due to a Col1a1 structural mutation, could attenuate the phenotype. In vitro, Aga2+/- osteoblasts show increased protein kinase RNA-like endoplasmic reticulum kinase (PERK) activation protein levels, which improved upon treatment with 4-PBA. The in vivo data demonstrate that a postweaning 5-week 4-PBA treatment increased total body length and weight, decreased fracture incidence, increased femoral bone volume fraction (BV/TV), and increased cortical thickness. These findings were associated with in vivo evidence of decreased bone-derived protein levels of the ER stress markers binding immunoglobulin protein (BiP), CCAAT/-enhancer-binding protein homologous protein (CHOP), and activating transcription factor 4 (ATF4) as well as increased levels of the autophagosome marker light chain 3A/B (LC3A/B). Genetic ablation of CHOP in Aga2+/- mice resulted in increased severity of the Aga2+/- phenotype, suggesting that the reduction in CHOP observed in vitro after treatment is a consequence rather than a cause of reduced ER stress. These findings suggest the potential use of chemical chaperones as an adjunct treatment for forms of OI associated with ER stress. © 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).

Validity and Reliability of a Field Hockey-Specific Dribbling Speed Test.

ABSTRACT: Tapsell, LC, Binnie, MJ, Lay, BS, Dawson, BT, and Goods, PSR. Validity and reliability of a field hockey-specific dribbling speed test. J Strength Cond Res 36(6): 1720-1725, 2022-The present study aimed to design a valid and reliable test for field hockey players that concurrently assesses the skill of dribbling and sport-specific agility. In total, 27 male and 32 female subjects were recruited from amateur (n = 20), state-level (n = 22), and national-level (n = 17) field hockey teams. The test course was developed in consultation with state- and national-level field hockey coaches, and using match analyses from existing literature. Subjects were familiarized before completing a testing session that consisted of 3 maximal-effort trials through a field hockey-specific course while dribbling a hockey ball, and another 3 trials of the same course without dribbling the ball. Amateur and state subjects completed an additional session for test-retest reliability analysis. Electronic timing gates recorded time to complete the course with the ball (DRIBBLE), without the ball (SPRINT), and the difference between DRIBBLE and SPRINT (DELTA). With significance set at p < 0.05, subjects of higher playing levels recorded significantly faster DRIBBLE (p < 0.001) and significantly lower DELTA (p < 0.001) times. No significant difference was found between player levels for SPRINT (p = 0.484) times. Intraclass correlations were 0.84 and 0.81 for DELTA and DRIBBLE, respectively. In conclusion, the dribbling test trialed here has sufficient validity and reliability for use in performance testing of field hockey athletes and can be implemented across playing levels to objectively track skill progression.

COPB2 loss of function causes a coatopathy with osteoporosis and developmental delay.

Coatomer complexes function in the sorting and trafficking of proteins between subcellular organelles. Pathogenic variants in coatomer subunits or associated factors have been reported in multi-systemic disorders, i.e., coatopathies, that can affect the skeletal and central nervous systems. We have identified loss-of-function variants in COPB2, a component of the coatomer complex I (COPI), in individuals presenting with osteoporosis, fractures, and developmental delay of variable severity. Electron microscopy of COPB2-deficient subjects' fibroblasts showed dilated endoplasmic reticulum (ER) with granular material, prominent rough ER, and vacuoles, consistent with an intracellular trafficking defect. We studied the effect of COPB2 deficiency on collagen trafficking because of the critical role of collagen secretion in bone biology. COPB2 siRNA-treated fibroblasts showed delayed collagen secretion with retention of type I collagen in the ER and Golgi and altered distribution of Golgi markers. copb2-null zebrafish embryos showed retention of type II collagen, disorganization of the ER and Golgi, and early larval lethality. Copb2+/- mice exhibited low bone mass, and consistent with the findings in human cells and zebrafish, studies in Copb2+/- mouse fibroblasts suggest ER stress and a Golgi defect. Interestingly, ascorbic acid treatment partially rescued the zebrafish developmental phenotype and the cellular phenotype in Copb2+/- mouse fibroblasts. This work identifies a form of coatopathy due to COPB2 haploinsufficiency, explores a potential therapeutic approach for this disorder, and highlights the role of the COPI complex as a regulator of skeletal homeostasis.

Localized chondro-ossification underlies joint dysfunction and motor deficits in the Fkbp10 mouse model of osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a genetic disorder that features wide-ranging defects in both skeletal and nonskeletal tissues. Previously, we and others reported that loss-of-function mutations in FK506 Binding Protein 10 (FKBP10) lead to skeletal deformities in conjunction with joint contractures. However, the pathogenic mechanisms underlying joint dysfunction in OI are poorly understood. In this study, we have generated a mouse model in which Fkbp10 is conditionally deleted in tendons and ligaments. Fkbp10 removal substantially reduced telopeptide lysyl hydroxylation of type I procollagen and collagen cross-linking in tendons. These biochemical alterations resulting from Fkbp10 ablation were associated with a site-specific induction of fibrosis, inflammation, and ectopic chondrogenesis followed by joint deformities in postnatal mice. We found that the ectopic chondrogenesis coincided with enhanced Gli1 expression, indicating dysregulated Hedgehog (Hh) signaling. Importantly, genetic inhibition of the Hh pathway attenuated ectopic chondrogenesis and joint deformities in Fkbp10 mutants. Furthermore, Hh inhibition restored alterations in gait parameters caused by Fkbp10 loss. Taken together, we identified a previously unappreciated role of Fkbp10 in tendons and ligaments and pathogenic mechanisms driving OI joint dysfunction.

Understanding and interpretation of a variant of uncertain significance (VUS) genetic test result by pediatric providers who do not specialize in genetics.

The advancement of genetic testing technologies has allowed for better diagnosis and management of patients, but also results in more variants of uncertain significance (VUSs) due to the increased number of genes being analyzed. There are more genetic tests available and more providers who do not specialize in genetics ordering genetic testing, but few studies examining how providers who do not specialize in genetics interpret VUSs. This study surveyed pediatric providers at a midwestern pediatric care center who do not specialize in genetics about their understanding of a mock genetic test report with a VUS result and whether their understanding of the result was associated with experience ordering genetic tests. Participants' preferences about content of the report and steps taken to understand the result were also examined. Of the 51 participants, 33% correctly answered both knowledge questions about the VUS result: one asking them to interpret the result and one asking them how they would explain the result to the patient. There was no association between answering both knowledge questions correctly and types of previous genetic tests ordered (p > .1 for 8 types of genetic tests), having received a genetic test report with a VUS result (p = .58), having referred patients to a genetics professional (p = .74), or feeling comfortable discussing a positive, negative, or VUS genetic test result (p > .4). This suggests that having previous experience ordering genetic tests does not contribute to the participants' knowledge about a variant of uncertain significance. Most participants reported that the amount of information in each section of the mock report was adequate. Participants were likely to reference multiple resources to better understand a VUS result, including published literature (82%), gene-specific databases (67%), and colleagues (63%). While these results cannot be generalized to all institutions, institutions can use the two knowledge questions to determine participants' understanding of genetic test results. This will help healthcare institutions determine methods that will best aide their providers who order genetic testing but do not specialize in genetics in learning more about the genetic testing process and better utilize results to improve patient care.

Heat Added to Repeated-Sprint Training in Hypoxia Does Not Affect Cycling Performance.

PURPOSE: This study aimed to assess the influence of graded air temperatures during repeated-sprint training in hypoxia (RSH) on performance and physiological responses. METHODS: Ten well-trained athletes completed one familiarization and 4 experimental sessions at a simulated altitude of 3000 m (0.144 FIO2) above sea level. Air temperatures utilized across the 4 experimental sessions were 20°C, 25°C, 30°C, and 35°C (all 50% relative humidity). The participants performed 3 sets of 5 × 10 seconds "all-out" cycle sprints, with 20 seconds of active recovery between sprints and 5 minutes of active recovery between sets (recovery intensity = 120 W). Core temperature, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion, and thermal sensation were collected. RESULTS: There were no differences between conditions for peak power, mean power, and total work in each set (P > .05). There were no condition × time interaction effects for any variables tested. The peak core temperature was highest at 30°C (38.06°C [0.31°C]). Overall, the pulse oxygen saturation was higher at 35°C than at 20°C (P < .001; d < 0.8), 25°C (P < .001; d = 1.12 ± 0.54, large), and 30°C (P < .001; d = 0.84 ± 0.53, large). CONCLUSION: Manipulating air temperature between 20°C and 35°C had no effect on performance or core temperature during a typical RSH session. However, the pulse oxygen saturation was preserved at 35°C, which may not be a desirable outcome for RSH interventions. The application of increased levels of ambient heat may require a different approach if augmenting the RSH stimulus is the desired outcome.

Nitric oxide modulates bone anabolism through regulation of osteoblast glycolysis and differentiation.

Previous studies have shown that nitric oxide (NO) supplements may prevent bone loss and fractures in preclinical models of estrogen deficiency. However, the mechanisms by which NO modulates bone anabolism remain largely unclear. Argininosuccinate lyase (ASL) is the only mammalian enzyme capable of synthesizing arginine, the sole precursor for nitric oxide synthase-dependent (NOS-dependent) NO synthesis. Moreover, ASL is also required for channeling extracellular arginine to NOS for NO production. ASL deficiency (ASLD) is thus a model to study cell-autonomous, NOS-dependent NO deficiency. Here, we report that loss of ASL led to decreased NO production and impairment of osteoblast differentiation. Mechanistically, the bone phenotype was at least in part driven by the loss of NO-mediated activation of the glycolysis pathway in osteoblasts that led to decreased osteoblast differentiation and function. Heterozygous deletion of caveolin 1, a negative regulator of NO synthesis, restored NO production, osteoblast differentiation, glycolysis, and bone mass in a hypomorphic mouse model of ASLD. The translational significance of these preclinical studies was further reiterated by studies conducted in induced pluripotent stem cells from an individual with ASLD. Taken together, our findings suggest that ASLD is a unique genetic model for studying NO-dependent osteoblast function and that the NO/glycolysis pathway may be a new target to modulate bone anabolism.

Influence of Electronic Devices on Sleep and Cognitive Performance During Athlete Training Camps.

ABSTRACT: Jones, MJ, Dawson, B, Eastwood, PR, Halson, SL, Miller, J, Murray, K, Dunican, IC, Landers, GJ, and Peeling, P. Influence of electronic devices on sleep and cognitive performance during athlete training camps. J Strength Cond Res 35(6): 1620-1627, 2021-This study investigated the effects of removing athletes' electronic devices in the evening on sleep and performance during training camps. Water polo athletes (n = 26) attending a 7-night training camp (study 1) and triathletes (n = 23) attending a 4-night training camp (study 2) were randomly allocated to a no-device group (no electronic devices could be used after dinner or overnight; ND) or control group (unrestricted electronic device use; CON). Sleep was monitored through wrist actigraphy. The ND group completed a questionnaire measuring anxiety related to being unable to use electronic devices ("nomophobia"). Triathletes also completed a psychomotor vigilance test (PVT) at the start and end of camp. Water polo ND athletes went to bed earlier and spent longer time in bed than CON on the first night, but not on other nights. In triathletes, sleep quantity was not different between groups on any night. No statistically significant differences were observed for changes in nomophobia from the first to the last night of camp. No differences in PVT performance were observed between ND and CON triathletes. In conclusion, removal of evening electronic devices does not improve sleep quantity or cognitive performance in athletes during short-duration (4-7 nights) training camps.

Repeat Application of Ischemic Preconditioning Improves Maximal 1,000-m Kayak Ergometer Performance in a Simulated Competition Format.

Halley, SL, Peeling, P, Brown, H, Sim, M, Mallabone, J, Dawson, B, and Binnie, MJ. Repeat application of ischemic preconditioning improves maximal 1,000-m kayak ergometer performance in a simulated competition format. J Strength Cond Res XX(X): 000-000, 2020-This study examined the effects of ischemic preconditioning (IPC) on repeat 1,000-m kayak ergometer time-trial (TT) performance, completed in a simulated competition format. Eight well-trained male kayak athletes performed 3 experimental trials, each consisting of two 1,000-m TTs separated by 80 minutes (TT 1 and TT 2). Trials included; (a) IPC (4 × 5 minutes 220 mm Hg alternating bilateral leg occlusion) 40 minutes before TT 1 only (IPC1); (b) IPC 40 minutes before TT 1 and 20 minutes before TT 2 (IPC2); and (c) no IPC (CON). Time, power, stroke rate, and expired gas variables (V[Combining Dot Above]O2 and accumulated oxygen deficit) were measured throughout each TT; blood gas variables (blood lactate, partial pressure of oxygen and blood pH) and rating of perceived exertion were measured before and after each effort. Physiological, perceptual, and physical measures were analyzed via a repeated measures analysis of variance with the level of significance set at p ≤ 0.05. There were large improvements in completion time for TT 1 in IPC1 (d = 1.24 ± 0.68, p < 0.05) and IPC2 (d = 1.53 ± 0.99, p < 0.05) versus CON. There was also a large improvement in TT 2 completion time in IPC2 versus CON (d = 1.26 ± 1.13, p = 0.03) whereas, IPC1 and CON were indifferent (d = 0.3 ± 0.54, p = 0.23). This study showed that a repeat application of IPC in a simulated competition format may offer further benefit in comparison to a single pre-exercise application of IPC.

Refining Treatment Strategies for Iron Deficient Athletes.

Iron deficiency (ID) is a prevailing nutritional concern amongst the athletic population due to the increased iron demands of this group. Athletes' ability to replenish taxed iron stores is challenging due to the low bioavailability of dietary sources, and the interaction between exercise and hepcidin, the primary iron-regulatory hormone. To date, copious research has explored the link between exercise and iron regulation, with a more recent focus on optimising iron treatment applications. Currently, oral iron supplementation is typically the first avenue of iron replacement therapy beyond nutritional intervention, for treatment of ID athletes. However, many athletes encounter associated gastrointestinal side-effects which can deter them from fulfilling a full-term oral iron treatment plan, generally resulting in sub-optimal treatment efficacy. Consequently, various strategies (e.g. dosage, composition, timing) of oral iron supplementation have been investigated with the goal of increasing fractional iron absorption, reducing gastric irritation, and ultimately improving the efficacy of oral iron therapy. This review explores the various treatment strategies pertinent to athletes and concludes a contemporary strategy of oral iron therapy entailing morning supplementation, ideally within the 30 min following morning exercise, and in athletes experiencing gut sensitivity, consumed on alternate days or at lower doses.

A global Slc7a7 knockout mouse model demonstrates characteristic phenotypes of human lysinuric protein intolerance.

Lysinuric protein intolerance (LPI) is an inborn error of cationic amino acid (arginine, lysine, ornithine) transport caused by biallelic pathogenic variants in SLC7A7, which encodes the light subunit of the y+LAT1 transporter. Treatments for the complications of LPI, including growth failure, renal disease, pulmonary alveolar proteinosis, autoimmune disorders and osteoporosis, are limited. Given the early lethality of the only published global Slc7a7 knockout mouse model, a viable animal model to investigate global SLC7A7 deficiency is needed. Hence, we generated two mouse models with global Slc7a7 deficiency (Slc7a7em1Lbu/em1Lbu; Slc7a7Lbu/Lbu and Slc7a7em1(IMPC)Bay/em1(IMPC)Bay; Slc7a7Bay/Bay) using CRISPR/Cas9 technology by introducing a deletion of exons 3 and 4. Perinatal lethality was observed in Slc7a7Lbu/Lbu and Slc7a7Bay/Bay mice on the C57BL/6 and C57BL/6NJ inbred genetic backgrounds, respectively. We noted improved survival of Slc7a7Lbu/Lbu mice on the 129 Sv/Ev × C57BL/6 F2 background, but postnatal growth failure occurred. Consistent with human LPI, these Slc7a7Lbu/Lbu mice exhibited reduced plasma and increased urinary concentrations of the cationic amino acids. Histopathological assessment revealed loss of brush border and lipid vacuolation in the renal cortex of Slc7a7Lbu/Lbu mice, which combined with aminoaciduria suggests proximal tubular dysfunction. Micro-computed tomography of L4 vertebrae and skeletal radiographs showed delayed skeletal development and suggested decreased mineralization in Slc7a7Lbu/Lbu mice, respectively. In addition to delayed skeletal development and delayed development in the kidneys, the lungs and liver were observed based on histopathological assessment. Overall, our Slc7a7Lbu/Lbu mouse model on the F2 mixed background recapitulates multiple human LPI phenotypes and may be useful for future studies of LPI pathology.

Using the interaction of speed and acceleration to detect repeated-sprint activity in team sports.

PURPOSE: To compare the occurrence and characteristics of repeated-sprint (RS) activity in elite team sport competition when classified according to speed and/or acceleration, and their interaction via metabolic power (Pmet). Methods: Elite male hockey players (N = 16) wore player-tracking devices in six international matches. Sprint efforts were defined using four separate classifications: speed >5.5 m∙s-1, acceleration >1.5 m∙s-2, speed-or-acceleration, and Pmet >25.5 W∙kg-1. RS bouts were defined as ≥3 efforts with mean recovery ≤21 s. For Pmet, RS bouts were also classified using a maximal recovery period ≤21 s. The number of sprint efforts and RS bouts, and the number of efforts, effort durations and recovery periods within RS bouts, were compared across each classification method, and between mean and maximal recovery criteria. Results: More RS bouts were identified via Pmet (8.5 ± 2.8) than either speed and/or acceleration, and comprised more efforts (4.0 ± 0.4) with shorter recovery periods (11.5 ± 1.8 s). Fewer RS bouts (7.3 ± 2.8 vs. 8.5 ± 2.8) were identified with a maximum rather than mean recovery criterion. Conclusions: Definitions of sprint efforts and recovery periods which reflect ATP depletion and replenishment via Pmet suggest that RS activity occurs frequently in team sport competition, and is more demanding than when speed and/or acceleration are used to define RS activity in variable-speed locomotion.