Physiologia, Volume 4, Issue 4 (December 2024) – 16 articles

The pervasive presence of per- and polyfluoroalkyl substances (PFAS) in the environment and their persistent nature raise significant concerns regarding their impact on human health. This review delves into the obesogenic potential of PFAS, shedding light on their mechanisms of action, epidemiological correlations with obesity and metabolic disorders, and the challenges faced in regulatory frameworks. PFAS, characterized by their carbon-fluorine chains, are ubiquitous in various consumer products, leading to widespread exposure through ingestion of contaminated food and water. Emerging evidence suggests that PFAS may act as endocrine-disrupting chemicals, interfering with lipid metabolism and hormone functions related to obesity. We examine in vitro, in vivo, human, and in silico studies that explore the interaction of PFAS with PPARs and other molecular targets, influencing adipogenesis and lipid homeostasis. Furthermore, the review highlights epidemiological studies investigating the association between maternal PFAS exposure and the risk of obesity in offspring, presenting mixed and inconclusive findings that underscore the complexity of PFAS effects on human health. Presently, there are major challenges in studying PFAS toxicity, including their chemical diversity and the limitations of current regulatory guidelines, potential remediation, and detoxification. This review emphasizes the need for a multidisciplinary approach, combining advanced analytical methods, in silico models, and comprehensive epidemiological studies, to unravel the obesogenic effects of PFAS and inform effective public health strategies. Full article

Background: Ultra-short race-pace training (USRPT) is designed to accustom swimmers to the pace of an event by using high volume and submaximal intensity with short intervals. However, due to imprecise data on volume and interval, further investigation is necessary. This scoping review aims to provide evidence-based insights into the advantages and disadvantages of recommended volumes and intervals during USRPT, guiding swimming coaches and offering practical advice regarding this training method. Methods: For this analysis, 90,613 studies from PubMed, Scopus, Web of Science, and Google Scholar were screened to examine the volume and interval of the USRPT method. Results: Only five studies met the inclusion criteria, were further assessed using a PRISMA-P document, and were analyzed for biases with the revised Cochrane risk-of-bias tool for randomized crossover trials. Excessive daily use of USRPT in training volume is discouraged due to potential psychological strain. Reaching failure should involve modifying variables such as intensity and interval. Additionally, interval periods should vary based on the targeted event’s physiological demands and the USRPT set’s volume. For short-distance events (50–100 m), it is recommended that USRPT protocols include a work-to-rest ratio of 1:1 or 1:2, allowing more time for aerobic contribution to replenish energy supplies (consistent with HIIT and SIIT principles). Conclusions: Further research on specific elements of USRPT, including volume and interval, is essential to identify the most effective training sets for swimmers across different distances and styles. Full article

Background: Oestradiol has been implicated as a factor in substrate utilisation in male and mouse studies but the effect of acute changes during the menstrual cycle is yet to be fully understood. Objective: To determine the role of oestradiol in respiratory exchange ratio (RER) during exercise at various intensities. Methods: This systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. From inception to November 2023, four online databases (Cochrane, SPORTDiscus, MEDline and Web of Science) were searched for relevant articles. Studies that reported a resting oestradiol measurement in naturally menstruating women with exercise at a percentage of maximal aerobic capacity (%V˙O_2max) were included. Mean and standard deviation for oestradiol, RER and exercise intensity were extracted and study quality assessed using a modified Downs and Black checklist. Risk of bias was assessed using I₂ measure of heterogeneity and Egger’s regression test, assessment of bias from methodological quality was identified by sensitivity analysis. Eligible datasets were extracted for pairwise comparisons within a meta-analysis and correlation between change in oestradiol and change in RER. Data were also pooled to produce a mean and standard deviation for RER for menstrual stage and for low and high oestradiol groups. Results: Twenty-four articles were identified, over 50% were identified as high quality. Sixteen articles included datasets eligible for meta-analysis. Eleven articles utilised a submaximal constant-load exercise intensity, finding a standardised mean difference of − 0.09 ([CI: −0.35–0.17], p = 0.5) suggesting no effect of menstrual phase on constant-load exercise RER. In six articles using incremental exercise tests to exhaustion, a standardised mean difference of 0.60 ([CI 0.00–1.19], p = 0.05) was identified towards a higher maximal RER attained in follicular compared to luteal phase. There was no correlation (R = −0.26, p = 0.2) between change in oestradiol and change in RER between phases. All 24 articles, totalling 650 participants, were included in pooled analysis. When grouped by menstrual cycle phase or when grouped by oestradiol levels, RER was higher in the follicular phase than the luteal phase at low and high constant load exercise intensities. Discussion: Findings from the pooled-analysis and meta-analysis suggest that there may be menstrual cycle phase differences in RER that are intensity dependent. These differences may be related to sex hormone levels, but this was not supported by evidence of correlation between differences in RER and differences in oestradiol. At present, it remains best practice to assess performance in the same menstrual cycle phase if seeking to assess change from baseline. Full article

Objective: This study aimed to perform an umbrella review of existing systematic reviews on the effects of saddle position on cycling. Material and methods: We conducted a systematic search across the electronic databases EBSCO, PubMed, Scopus, Web of Science, and B-On for systematic reviews investigating the effects of saddle position on cycling, following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. To prevent the risk of bias, two researchers independently performed the search. To evaluate the methodological quality of the included reviews, the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR 2) checklist was used. Results: A total of seven systematic reviews that met the eligible criteria were included. The systematic reviews showed high heterogeneity among themselves (e.g., type of included studies, participants’ characteristics, or evaluated outcomes) and low to critically low methodological quality. Relationships have been found between the rider’s saddle position and health issues (such as low back pain (four studies), knee injury or pain (three studies), lumbar kyphosis (one study), and impact on perineum (two studies)), and on performance alterations (such as, muscle activation, oxygen uptake, load and intensity, efficiency (one study), and comfort (one study)). The results showed that some research provided conflicting evidence in regard to the studied relations (e.g., knee injury or pain, impact on perineum, and efficiency). Conclusions: Cyclists’ saddle position impacts various issues related to health and performance. More research is needed, and future studies should focus on the clarification of the conflicting evidence observed in this review. Full article

Background: Combining pool-based and resistance workouts, both in the pool and on dry land, is a valuable approach to enhancing swimming performance. However, few investigations have been conducted on this topic. Through a randomized controlled trial study, we investigated the effects of a 10-week concurrent resistance training program, which integrated resistance workouts both in the pool and on dry land on tethered force, lower limbs strength, anaerobic critical velocity, and swimming performance, in regional age-group breaststroke swimmers. Methods: Regional age-group swimmers (N = 24, males) were randomly divided into two groups. The experimental group (EG: 15.1 ± 0.5 years old) performed combined pool-based + resistance workouts, both in the pool and on dry land. The control group (CG: 15.1 ± 0.7 years old) performed their usual training regime, i.e., pool-based + resistance workouts on dry land only. The tethered swimming force, muscular strength, anaerobic critical velocity, and swimming performance and technique of the swimmers were evaluated before the training program began and after 10 weeks. Results: Improvements were observed in the EG vs. the CG in terms of the mean force (30.04%, p = 0.02; d = 0.75), one-repetition maximum back squat (20.57%, p = 0.01; d = 2.05), maximal force (19.23%, p = 0.03; d = 0.69), and anaerobic critical velocity (4.2%, p = 0.04; d = 0.61). The 50 and 200 m breaststroke performance times improved (4.3 and 5.4%, p = 0.01, d = 0.88–0.92, respectively) after 10 weeks. Conclusions: With the increasing demands of contemporary swimming competitions, which often include heats, semifinals, and finals, achieving optimal physical fitness to compete at an elite level, in every round, is vital for swimmers. The combination of resistance training workouts both in the pool and on dry land seems to enhance swimming performance in age-group swimmers, particularly in sprint to middle-distance breaststroke swimmers. Full article

Background: Tendon lesions affecting the proximal rectus femoris (PRF) muscle represent about 1.5% of hip injuries. Most acute cases are managed conservatively with physiotherapy. There is a lack of consensus regarding surgical intervention for chronic injuries. This article, alongside a literature review, presents a case of anatomical surgical reinsertion for chronic complete avulsion rupture of the PRF tendon. Case Report: A 34-year-old amateur athlete experienced acute inguinal pain from overexertion, with conservative treatment having failed over 3 months. Seven months later, proximal tendon rupture involving both PRF muscle heads was confirmed. An anterior Hueter approach released the tendon from the adhesions and fibrosis. The direct portion was reinserted into the inferior anterior iliac spine, and the reflex portion was reattached to the supraacetabular groove. The patient showed excellent improvement on the modified Harris Hip and Lysholm–Tegner scales. The quadriceps muscle force decreased by 20% compared to the contralateral leg at 3 months, reducing to 4% by 12 months. Normal activities resumed after six weeks, and sports resumed after 4 months. Conclusions: The patient experienced significant postoperative improvement, as shown by the enhanced functional scores and muscle force recovery over one year. The success of the anatomical reconstruction in restoring tendon continuity underscores the importance of tendon healing mechanisms, including tissue remodeling and revascularization, in chronic avulsion injuries. This case highlights the efficacy of anatomical reconstruction for chronic PRF tendon avulsion. The literature review offers further insights into treatment options and the physiological basis of recovery for such injuries. Full article

Background: Ketone body supplementation has emerged as a potential ergogenic aid in cycling. Exogenous ketones, primarily in the form of beta-hydroxybutyrate, offer an alternative fuel source, bypassing the need for strict ketogenic diets. However, the science surrounding their efficacy remains complex, with mixed field findings and unexplored mechanisms. Methods: A narrative review of the current literature was conducted, synthesizing studies on the metabolic and cognitive effects of ketone bodies in cycling. The review included an examination of human and mechanistic studies, along with emerging hypotheses on ketone bodies and their role in modulating red blood cell production and recovery processes. Results: Ketone body supplementation can theoretically spare glycogen, reduce muscle protein breakdown, enhance fat oxidation, and improve recovery by mitigating oxidative stress and inflammation. Additionally, ketone bodies may support cognitive function, reducing perceived mental fatigue. Preliminary evidence also suggests a potential role in modulating erythropoietin levels through histone acetylation, though further research is needed to establish its impact on oxygen delivery. Despite the theoretical potential, the practical assessment of field studies shows disappointing effects on performance from ketone body supplementation. Conclusions: While ketone bodies offer several potential benefits for cyclists, the variability in individual responses, lack of long-term data, and inconsistent findings in performance studies highlight the need for further research. Optimizing dosage, timing, and understanding the broader implications of ketone body supplementation will be crucial for their practical application in cycling. Full article

Military personnel routinely complete stressful training exercises in harsh environmental conditions to prepare for intense operational demands. Purpose: This study determined the effect of environmental conditions on salivary hormone profiles in Marines during a mountain warfare training exercise (MTX). Methods: Two cohorts of Marines (age 22 ± 4, height 174 ± 7 cm, body mass 79.2 ± 11.5 kg) completed an MTX (elevation 2100 to 3500 m) in the Fall (n = 63, temperature 11 ± 2 °C) and Winter (n = 64, temperature −5 ± 4 °C). Saliva samples were provided before (PRE), during (MID), and after (POST) the MTX, and were assayed for α-amylase, cortisol, DHEA, testosterone, and osteocalcin. Results: Linear mixed models were used to determine significant interactions (time × season) and found differences in DHEA, testosterone, and osteocalcin. Testosterone and DHEA were lower at MID compared to PRE and POST during the Fall MTX. Testosterone was higher at MID compared to PRE and POST during the Winter MTX, while DHEA remained stable. Osteocalcin was higher in Fall participants compared to Winter but demonstrated a similar trend to increase at MID and decrease at POST in both groups. Cortisol was higher during the Winter MTX compared to the Fall. Conclusions: These findings highlight the differential physiological stress responses in varying seasonal conditions, suggesting the need for tailored training strategies to enhance military readiness and prevent hormonal dysregulation. Further research is needed to elucidate the mechanisms underlying these seasonal effects. Full article

The brain-derived neurotrophic factor (BDNF) is a crucial protein in the development of the cognitive system. It regulates the growth of neurons and glial cells, synaptic plasticity, and neuroprotection. Background/Objectives: It has been suggested that high-intensity exercise could modulate the mechanisms of BDNF release, with potentially significant implications in the professional sports world. However, this is not yet fully proven, and the underlying physiological alterations are unknown. Methods: This paper reviews the current scientific literature to clarify the uncertainties about how high-intensity physical exercise influences BDNF release and its relationship with high-performance sports. Results: Strenuous exercise appears to increase BDNF synthesis through the action of lactate and the PGC-1α/FNDC5 pathway. Additionally, cognitive function has been described as an element to consider for maximizing sports performance. Conclusions: In this regard, this review provides a solid starting point for further investigation into the molecular mechanisms that promote BDNF expression mediated by exercise, as well as for seeking a direct correlation between the role of cognitive development and athletic performance in high-performance athletes. Full article

Background: Individuals observe Ramadan fasting for ~11 h per day for 28–30 days, which can negatively affect lean mass. Resistance training or increased protein intake can potentially preserve lean mass in these individuals. Methods: Twenty-three young and healthy adult Muslim men were divided into three groups: Ramadan fasting (RAM), Ramadan fasting combined with resistance training (RAM + RT), and Ramadan fasting combined with 30 g of daily whey protein (RAM + WH). Participants’ body mass, body mass index (BMI), body fat percentage, fat mass, and lean mass were measured the week prior to and during the last week of Ramadan via a stadiometer and dual-energy X-ray absorptiometry (DXA). Results: Body mass (kg) was decreased for all three groups (RAM = −1%, RAM + RT = −1%, RAM + WH = −1.3%; p = 0.033), though there were no differences between groups. Lean mass (kg) was decreased for all three groups (RAM = −1%, RAM + RT = −1%, RAM + WH = −2%; p = 0.013), though there were no differences between groups. No differences were observed for body weight, BMI, or body fat percentage. Conclusions: These results indicate resistance training or whey protein did not provide any advantage for preserving lean mass in individuals participating in Ramadan fasting. Full article

Background/Objectives: Endurance triathlons impose substantial physiological stress, yet the effects of short-course formats remain relatively unexplored. This preliminary study presents novel findings on proteinuria and hydration levels in well-trained triathletes. Methods: 27 participants (41.9 ± 7.4 years) who completed a sprint triathlon consisting of a 1500 m swim, 26 km cycle, and 8 km run. Urine samples were collected before and after the race. Results: Our results revealed a significant increase in post-race proteinuria cases from four to nine (p = 0.03) and the first reported case of post-race urobilinuria and ketoacidosis in this context. Additionally, pre-race glucosuria, present in nine cases, decreased to three post-race. Hematuria cases decreased from six to two (p = 0.13) and pre-race leukocyturia resolved post-race. There was a significant increase in urine specific gravity (from 1.018 to 1.023, p = 0.03), indicating dehydration. Conclusions: Short-course triathlons significantly induced post-race proteinuria, urobilinuria, and dehydration, highlighting the substantial physiological stress on kidney function and hydration status despite the shorter distances. These findings underscore the importance of monitoring urinary biomarkers and hydration levels in athletes before and after competition. Full article

Whilst cold therapies such as cold-water immersion are regularly used in practice, the practical application does not always align with best practices. In this commentary, we highlight the key components of the British Association of Sport and Exercise Sciences (BASES) Expert Statement on the use of cooling therapies for post-exercise recovery and provide additional discussion on the empirical evidence and rationale that informed our perspective. We developed a series of specific questions to ensure that cold therapy recovery protocols are context-specific and tailored to the needs of the individual athletes. These questions, which cover the WHEN, WHAT, and HOW of cold therapy, were central to the development of the Expert Statement. This was presented as a decision tree to ensure that key messages could be concisely disseminated across a range of sporting environments and populations (e.g., gyms, locker rooms, and treatment rooms), supporting and informing decision-making for those wanting to use cold therapy to assist their recovery in line with previously published peer-reviewed work. Discussion points included the suitability of cooling therapies in some contexts, how athletes’ choice of cooling mode should be largely driven by practicalities (e.g., budget and availability), and, lastly, future research directions. Full article

Background/Objectives: This study aimed to evaluate the effects of an 8-week combined plyometric and resistance training program on the physical fitness (PF) of adolescent girls aged 12 to 15 years. The objective was to determine whether combined training (CT) would yield greater improvements in performance measures compared to resistance training (RT) alone. Methods: Forty-seven adolescent girls were randomly assigned to either the CT group or the RT group. Performance measures such as the 20 m sprint, squat jump, vertical jump, handgrip strength, and flexibility (sit and reach test) were assessed before and after the 8-week intervention. Changes in these measures were analyzed to compare the effects of the two training approaches. Results: The CT group showed a significant reduction in sprint time (−6.5%) compared to the RT group (−4.1%), although the difference was not statistically significant. Squat jump height improved significantly by 5.6% in the CT group compared to 1.1% in the RT group (p < 0.05). Similarly, vertical jump height increased by 6.7% in the CT group and by 2.4% in the RT group (p < 0.05). Handgrip strength improved by 7.5% in the CT group and 4.6% in the RT group, with no significant differences between the groups. Flexibility showed slight, non-significant improvements in both groups. Conclusions: The findings suggest that a combined plyometric and RT program is more effective in enhancing explosive power, specifically squat and vertical jump performance, in adolescent girls compared to RT alone. These results highlight the potential of CT programs for improving overall physical performance in this population. Full article

Background/Objectives: The purpose of this study was to investigate the effect of a short-term passive post-exercise heat acclimation (HA) protocol on anaerobic performance in college students. Methods: In total, 28 participants (age 22.3 ± 2.1 years, height 168 ± 9.1 cm, mass 71.5 ± 16.6 kg) volunteered and were randomly divided into either an intervention (INT) or control (CON) group. Both groups followed a consecutive two-day protocol, consisting of a 25 min submaximal cycle @ 50–60% heart rate reserve (HRR), followed by a 25 min hot water immersion (INT) or nothing (CON). All participants performed a 30 s Wingate Anaerobic Test (WAnT) on four separate occasions—familiarization, pre-intervention, acutely post-intervention, and 24 h post intervention. The WAnT measured their peak power (W), relative peak power (W/kg), mean power (W), fatigue index (%), and total work (kJ). Results: From the results of the Factorial ANOVA, it was found that there were no significant differences, with no main effect for group (INT vs. CON) or time (Trials 1–4) and no significant interaction across all measured variables (p > 0.05). Conclusions: A two-day post-exercise passive HA protocol utilizing hot water immersion had no significant effect on the measurement of anaerobic performance in college students. Full article

Mitochondria are crucial for cellular functioning, serving as both an intracellular energy source and a signaling organelle. Recent evidence also highlights their existence outside of cells, where they participate in cell-to-cell communication. Cardiometabolic disease (CMD) has a complex pathogenesis closely associated with mitochondrial dysregulation, inflammation, and metabolic abnormalities. This review explores the roles of circulating extracellular mitochondria (CEMI) in CMD, detailing how their various forms, whether as intact structures or within vesicles, contribute to CMD pathogenesis. We classify different forms of CEMIs and discuss their potential as biomarkers and therapeutic agents in CMDs. We also describe mitochondrial transplantation as an emerging therapy for restoring cellular function in damaged tissues. Finally, to standardize CEMI assessment, we propose the Universal CEMI Assessment Protocol (UCAP), a framework aimed at enhancing comparability and reproducibility across studies. Full article

Firefighting is a physically demanding occupation that requires optimal fitness and coordination in addition to other physical and cognitive skills. When firefighters lack the physical fitness necessary to perform their duties, they put themselves and others in danger of injury and even death. The heavy, unbreathable personal protective equipment worn to shield firefighters from harmful conditions also promotes overall performance decrements via restricted range of motion as well as energy expenditure and heat-related fatigue. Firefighters are expected to carry other heavy loads, such as hose packs, tools, and victims, while working in hazardous environments. In addition to external load carriage, many firefighters also carry excess body fat that may contribute to poor physical fitness and performance. Therefore, it is imperative to incorporate training strategies to optimize load carriage and improve body composition for improved physical performance during emergencies. Thus, the aims of this narrative review are to (1) explore the impact of firefighter-specific issues on physical performance and safety and (2) identify strategies to assess and optimize occupational performance and safety. Plyometrics; resistance training; and exercise selection, volume, and intensity specifically for improving physical performance in firefighters will be discussed. Full article