Athlete or Non-athlete? This Is the Question in Body Composition

Navigating Anthropometric Assessment in Sports Settings: Perspectives from ISAK Practitioners in the UK and Ireland

BACKGROUND

Anthropometric assessment in high-performance sports is complex, requiring both physical and psychological considerations. Despite the increasing number of International Society for the Advancement of Kinanthropometry (ISAK) accredited practitioners, the ethical and practical challenges they face-particularly in applying anthropometric data within dynamic sports environments-remain underexplored.

AIM

This qualitative study explores ISAK practitioners' experiences of anthropometric assessment in high-performance sport, identifying key challenges and practitioner-informed strategies to enhance practice and athlete well-being.

METHOD

Three on-line focus groups were conducted in August and September 2024 with 14 UK- and Ireland-based practitioners (11 female, three male), aged 44.0 ± 7.2 years. Participants had 10.6 ± 5.5 years of experience as ISAK Level 3 accredited practitioners and 11.0 ± 5.9 years of experience providing anthropometric support in sport, with 92% having worked at the international level. A semi-structured topic guide was used to facilitate discussion, and data analysis followed Braun and Clarke's reflexive thematic analysis framework.

RESULTS

Three key themes were identified: (1) Holistic athlete care: Integrating anthropometric and performance data; (2) Bridging the gap: Enhancing education and training for real-world application; and (3) Challenging the status quo: Addressing cultural and organisational barriers. Participants emphasised the importance of holistic, individualised approaches to anthropometric assessment that resist reductionist views of body metrics. They advocated for structured mentorship, expanded professional development, and greater interdisciplinary collaboration to support ethical and effective practice.

CONCLUSIONS

Entrenched data-driven cultures and hierarchical structures hinder athlete-centred care. Overcoming these barriers requires collaboration between regulatory bodies, ISAK practitioners, and multidisciplinary teams. Integrating frameworks such as Entrusted Professional Activities and Communities of Practice, alongside experiential learning approaches, will enhance practitioner autonomy and ensure anthropometric assessment remains both effective and athlete centred.

Anthropometric-based predictive equations developed with multi-component models for estimating body composition in athletes

PURPOSE

Body composition can be estimated using anthropometric-based regression models, which are population-specific and should not be used interchangeably. However, the widespread availability of predictive equations in the literature makes selecting the most valid equations challenging. This systematic review compiles anthropometric-based predictive equations for estimating body mass components, focusing on those developed specifically for athletes using multicomponent models (i.e. separation of body mass into ≥ 3 components).

METHODS

Twenty-nine studies published between 2000 and 2024 were identified through a systematic search of international electronic databases (PubMed and Scopus). Studies using substandard procedures or developing predictive equations for non-athletic populations were excluded.

RESULTS

A total of 40 equations were identified from the 29 studies. Of these, 36 were applicable to males and 17 to females. Twenty-six equations were developed to estimate fat mass, 10 for fat-free mass, three for appendicular lean soft tissue, and one for skeletal muscle mass. Thirteen equations were designed for mixed athletes, while others focused on specific contexts: soccer (n = 8); handball and rugby (n = 3 each); jockeys, swimming, and Gaelic football (n = 2 each); and futsal, padel, basketball, volleyball, American football, karate, and wheelchair athletes (n = 1 each).

CONCLUSIONS

This review presented high-standards anthropometric-based predictive equations for assessing body composition in athletes and encourages the development of new equations for underrepresented sports in the current literature.

Agreement between fat-free mass from bioelectrical impedance analysis and dual-energy X-ray absorptiometry and their use in estimating resting metabolic rate in resistance-trained men

BACKGROUND

This study aimed to determine the agreement between fat-free mass (FFM) estimates from bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) and their use in estimating resting metabolic rate (RMR) in men undergoing resistance training.

METHODS

Thirty healthy resistance-trained men (22.7 ± 4.4 years, 70.0 ± 8.7 kg, 174.6 ± 6.7 cm, and 22.9 ± 2.3 kg/m2) were evaluated. The equation developed by Tinsley et al. (RMR = 25.9 × fat-free mass [FFM] + 284) was adopted to calculate the RMR. DXA was used as the reference method for FFM.

RESULTS

Furthermore, FFM was also estimated by BIA using a spectral device. No significant difference (p > 0.05) was observed between DXA (1884.2 ± 145.5 kcal) and BIA (1849.4 ± 167.7 kcal) to estimate RMR. A positive and significant correlation (r = 0.89, p < 0.05) was observed between DXA and BIA estimates of RMR. The mean difference between methods indicated that BIA presented a bias of -34.8 kcal.

CONCLUSION

These findings suggest that using FFM derived from DXA or BIA results in similar RMR estimates in resistance-trained men.

Trails, traits, and mental states: Psychological differences between competitive and recreational sub-ultra and ultramarathon runners

Psychological trait differences between ultrarunners (completing more than a standard 42.195 km marathon) and sub-ultrarunners (≤42.195 km) have been assumed, but not robustly examined. The current study investigated trait differences between competitive and recreational runners at sub-ultra and ultramarathon distances. Six hundred and eleven participants (334 recreational, 400 sub-ultrarunner) completed an online, anonymous survey assessing five traits: mental toughness (MT), grit, motivation, general self-efficacy (GSE), and personality. Bayesian ANOVAs indicated at least moderate evidence for differences within Distance for grit-perseverance of effort (PE) and intrinsic motivation (IM), such that ultrarunners scored higher than sub-ultrarunners. Similarly, we observed at least moderate evidence that competitive runners scored higher than recreational runners on overall grit, grit-PE, GSE, IM, and extrinsic motivation (EM). Interaction effects provided moderate evidence for greater MT and overall grit in competitive ultrarunners. Evidence for other differences were anecdotal or favoured the null hypothesis. This study represents a novel investigation into the psychological makeup of runners. We suggest that aspects of motivation, grit, and self-efficacy, but not personality, may differentiate competitive from recreational runners, and ultrarunners from sub-ultrarunners. The identification of these trait differences may benefit runners and coaches wanting to progress in distance or competition level, with broader application to workplace or academic contexts. Further research is needed to develop a clearer conceptualisation of mental toughness, and build upon the novel findings of this study, particularly given the paucity of literature that exists within this context.

Nutrition for Children and Adolescents Who Practice Sport: A Narrative Review

At a developmental age, adequate physical activity is fundamental to overall health and well-being and preventing obesity. Moreover, establishing active behavior can help children and adolescents meet their growth and neurodevelopmental goals. Nutritional requirements vary according to intensity, frequency, and practiced physical activity or sport; therefore, pediatricians should give children and adolescents and their families adequate counseling, avoiding both nutrient deficiencies and excessive or inadequate supplement intake. The focus should be not only on sports performance but also on the child's well-being, growth, and neurodevelopment. Our narrative review aims to discuss the nutritional needs of children and adolescents who practice physical activity, non-competitive sports activity, and elite sports activity while also analyzing the role of food supplements and the risk of eating disorders within this category of subjects.

Review of Athletic Guidelines for High-Altitude Training and Acclimatization

Ramchandani, Rashi, Ioana Tereza Florica, Zier Zhou, Aziz Alemi, and Adrian Baranchuk. Review of athletic guidelines for high-altitude training and acclimatization. High Alt Med Biol. 00:000-000, 2024. Introduction: Exposure to high altitude results in hypobaric hypoxia with physiological acclimatization changes that are thought to influence athletic performance. This review summarizes existing literature regarding implications of high-altitude training and altitude-related guidelines from major governing bodies of sports. Methods: A nonsystematic review was performed using PubMed and OVID Medline to identify articles regarding altitude training and guidelines from international governing bodies of various sports. Sports inherently involving training or competing at high altitude were excluded. Results: Important physiological compensatory mechanisms to high-altitude environments include elevations in blood pressure, heart rate, red blood cell mass, tidal volume, and respiratory rate. These responses can have varying effects on athletic performance. Governing sport bodies have limited and differing regulations for training and competition at high altitudes with recommended acclimatization periods ranging from 3 days to 3 weeks. Discussion: Physiological changes in response to high terrestrial altitude exposure can have substantial impacts on athletic performance. Major sport governing bodies have limited regulations and recommendations regarding altitude training and competition. Existing guidelines are variable and lack substantial evidence to support recommendations. Additional studies are needed to clarify the implications of high-altitude exposure on athletic ability to optimize training and competition.

Assessment of Maximal Oxygen Uptake (VO2 Max) in Athletes and Nonathletes Assessed in Sports Physiology Laboratory

BACKGROUND

 Athletes' physical prowess plays a crucial role in their ability to succeed in any sporting endeavor. Each athlete on the field must have an exceptional aerobic capacity to withstand fierce competition and stringent regulatory guidelines. Maximal oxygen uptake (VO2 max) is a quantitative measure of aerobic capacity and is regarded as one of the most reliable indicators of cardiorespiratory and overall physical fitness of an individual by sports physiologists. The study aims to evaluate the VO2 max of athletes in comparison with nonathletes during treadmill and lower limb cycle ergometry exercises as assessed in the Sports Physiology Laboratory of a rural medical college. Treadmill exercise and bicycle ergometer exercise are the most common to perform as indoor aerobic exercises to assess one's physical fitness. Both these tests are equally useful in eliciting cardiac and vascular responses, so both these modalities were used to assess aerobic fitness.

METHODS

 This cross-sectional study, which examined participants aged 17-25, included 30 athletes (cases) and 120 age- and sex-matched controls. The VO2 max was evaluated using the Metabolic Module of Lab Chart Software, which was investigated through the PowerLab data acquisition system, AD Instruments (Bella Vista, NSW, Australia).

RESULTS

 The mean age of male athletes was 20.51 ± 2.69 years and of female athletes was 20.53 ± 1.62 years. The mean and standard deviation of VO2 max on the treadmill for male cases was 52.37 ± 8.78 mL/kg/min and for female cases was 40.96 ± 4.06 mL/kg/min, and on a cycle ergometer for male cases was 45.21 ± 9.43 mL/kg/min and for female cases was 34.32 ± 5.12 mL/kg/min. For the control group, the mean age of control males was 21.2 ± 2.62 years and of control females was 20.36 ± 1.5 years. The mean and standard deviation of VO2 max on the treadmill for control males was 33.35 ± 3.77 mL/kg/min and for control females was 25.09 ± 7.07 mL/kg/min, and on the cycle ergometer for control males was 34.17 ± 2.75 mL/kg/min and for control females was 24.15 ± 5.35 mL/kg/min.

CONCLUSION

This study showed significantly (p < 0.001) higher VO2 max levels in athletes of both genders compared to their age- and sex-matched controls upon exercise on the treadmill and cycle ergometer. This study underscores the significance of better cardiorespiratory fitness in athletes than nonathletes, giving pertinent insights about their aerobic capacity, which is precisely measured and expressed in terms of VO2.

What makes an athlete? A scoping review: Assessing the use of the word athlete with anterior cruciate ligament rehabilitation review studies. Is there a standard?

The term athlete does not currently have an agreed definition or standardized use across the literature. We analyzed the use of the term "athlete" amongst review studies specific to Anterior Cruciate Ligament (ACL) rehabilitation to investigate if the term was justified in its use. A comprehensive review of a database was performed to identify review papers which used the term "athlete" in the title, and which were related to ACL rehabilitation and surveillance. These papers were analyzed and their source papers were extracted for review. Twenty-eight review papers were identified. Source studies were extracted and analyzed. After removal of duplicates 223 source papers were identified. Despite using the term "athlete" in the review study titles only 5/17 (10.7%) sufficiently justified the use of this term. The term athlete was used in 117/223 (52.5%) of the source studies. Of those, 78/117 source studies (66.7%) justified the term athlete. The remaining 39/117 (33.3%) papers where participants were stated to be athletes, gave no justification. The ambiguous use of the term athlete amongst published studies highlights the need for a definition or justification of the term to be used in studies. The lack of a standard definition leads to the potential for studies to dilute high quality data by the potentially differing rehabilitation requirements and access to resources available to those with varying exercise levels. The indiscriminate use of the term athlete could lead to participants with widely ranging physical activity levels being included in the same study, and being used to create clinical advice for all. Advice could potentially vary across those of differing physical activity levels.

Athletic bioimpedance-based equations underestimate fat free mass components in male elite soccer players: development and validation of new soccer-specific predictive models

BACKGROUND

Bioelectrical impedance analysis (BIA) is a rapid and user-friendly technique for assessing body composition in sports. Currently, no sport-specific predictive equations are available, and the utilization of generalized formulas can introduce systematic bias. The objectives of this study were as follows: (i) to develop and validate new predictive models for estimating fat-free mass (FFM) components in male elite soccer players; (ii) to evaluate the accuracy of existing predictive equations.

METHODS

A total of 102 male elite soccer players (mean age 24.7 ± 5.7 years), participating in the Italian first league, underwent assessments during the first half of the in-season period and were randomly divided into development and validation groups. Bioelectrical resistance (R) and reactance (Xc), representing the bioimpedance components, were measured using a foot-to-hand BIA device at a single frequency of 50 kHz. Dual-energy X-ray absorptiometry was employed to acquire reference data for FFM, lean soft tissue (LST), and appendicular lean soft tissue (ALST). The validation of the newly developed predictive equations was conducted through regression analysis, Bland-Altman tests, and the area under the curves (AUC) of regression receiver operating characteristic (RROC) curves.

RESULTS

Developed models were: FFM = - 7.729 + (body mass × 0.686) + (stature2/R × 0.227) + (Xc × 0.086) + (age × 0.058), R2 = 0.97, Standard error of estimation (SEE) = 1.0 kg; LST = - 8.929 + (body mass × 0.635) + (stature2/R × 0.244) + (Xc × 0.093) + (age × 0.048), R2 = 0.96, SEE = 0.9 kg; ALST = - 24.068 + (body mass × 0.347) + (stature2/R × 0.308) + (Xc × 0.152), R2 = 0.88, SEE = 1.4 kg. Train-test validation, performed on the validation group, revealed that generalized formulas for athletes underestimated all the predicted FFM components (p < 0.01), while the new predictive models showed no mean bias (p > 0.05), with R2 values ranging from 0.83 to 0.91, and no trend (p > 0.05). The AUC scores of the RROC curves indicated an accuracy of 0.92, 0.92, and 0.74 for FFM, LST, and ALST, respectively.

CONCLUSIONS

The utilization of generalized predictive equations leads to an underestimation of FFM and ALST in elite soccer players. The newly developed soccer-specific formulas enable valid estimations of body composition while preserving the portability of a field-based method.

Comparison of Bioelectrical Impedance Indices for Skeletal Muscle Mass and Intracellular Water Measurements of Physically Active Young Men and Athletes

BACKGROUND

Bioelectrical impedance analysis (BIA) is a minimally invasive, safe, easy, and quick technology used to determine body composition.

OBJECTIVES

We compared the relationship among impedance indices obtained using single-frequency BIA, multi-frequency BIA, bioelectrical impedance spectroscopy (BIS), and skeletal muscle mass (SMM) of physically active young men and athletes using the creatine (methyl-d3) dilution method. We also compared the SMM and intracellular water (ICW) of athletes and active young men measured using a reference stable isotope dilution and BIS method, respectively.

METHODS

We analyzed data from 28 men (mean age, 20 ± 2 y) who exercised regularly. Single-frequency BIA at 5 kHz and 50 kHz (R5 and R50), multi-frequency BIA (R250-5), and BIS (RICW) methods of determining the SMM were compared. The deuterium and sodium bromide dilution methods of obtaining the total body water, ICW, and extracellular water measurements were also used, and the results were compared to those acquired using bioimpedance methods.

RESULTS

The correlation coefficients between SMM and L2/R5, L2/R50, L2/R250-5, and L2/RICW were 0.738, 0.762, 0.790, and 0.790, respectively (P < 0.01). The correlation coefficients between ICW and L2/R5, L2/R50, L2/R250-5, and L2/RICW were 0.660, 0.687, 0.758, and 0.730, respectively (P < 0.001). However, the correlation coefficients of L2/R50, L2/R250-5, and L2/RICW for SMM and ICW were not significantly different.

CONCLUSIONS

Our findings suggest that single-frequency BIA at L2/R50, multi-frequency BIA, and BIS are valid for assessing the SMM of athletes and active young men. Additionally, we confirmed that the SMM and ICW were correlated with single-frequency BIA, multi-frequency BIA, and BIS. Bioimpedance technologies may be dependable and practical means for assessing SMM and hydration compartment status of active young adult males; however, cross-validation is needed.

Sympathovagal Balance and Body Shape Index in Elite and Amateur Athletes: The Relationship Unraveled

Background Heart rate variability (HRV) is one piece among a complex network of adaptations existent in athletes that help them gain a better understanding of their own physiology. Sympathovagal balance is one of the spectral components of HRV analysis and is used to assess the frequently changing oscillations of a healthy heart, which can help in gauging the response of cardiac function towards physiological stress during exercise. This index is extensively used in appraising cardiac autonomic modulation. An evaluation of body composition in athletes has become a critical consideration when tracking HRV, as it helps practitioners understand the role of the autonomic nervous system (ANS) in obesity. The body shape index (BSI), which is based on waist circumference (WC), is an anthropometric parameter with decent predictive ability when measuring centripetal obesity. In this regard, the current study is an attempt to unravel the relationship between BSI and sympathovagal balance during exercise performed on two different instruments (treadmill and ergometer) by elite and amateur athletes. Methods It was an observational case-control study that included 30 elite and 120 amateur athletes. Symptom-limited exercise testing was performed by athletes on a motorized treadmill and ergometer in the sports physiology laboratory of a rural medical college in central India. Different anthropometric parameters like BSI and body surface area (BSA) were also recorded. Short-term HRV extracted from electrocardiogram (ECG) recordings was obtained using the Power Lab system and HRV analysis by LabChart software. Results The sympathovagal ratio, i.e., ratio of low frequency (LF) to high frequency (HF) in elite and amateur male populations showed a higher value than that in females, indicating a dominant sympathetic response in the males. There was a significant (p=0.042) positive correlation (r=0.24) between BSI and LF/HF Ratio in amateur females during treadmill exercise, whereas a significant (p=0.049) negative correlation (r=-0.27) was obtained in amateur males during ergometer exercise. Hence, increased weight and BSI were found to be associated with high sympathetic dominance, indicating a sympathovagal imbalance. Conclusion We attempted to explore the interaction between BSI and LF/HF during exercise performed on two different instruments (treadmill and ergometer) by elite and amateur athletes, which can help in testing the response of cardiac function to stress experienced during exercise. The study's uniqueness stems from discovering the relationship between BSI and HRV and how this relationship impacts sports performance. BSI measurement in athletes, both elite and amateur, allows for the assessment and forecasting of potential autonomic activity under exercise-induced stress by linking HRV with BSI.

Estimating fat-free mass in recreationally resistance-trained young men: Longitudinal and cross-sectional validation of different methods

Several techniques exist to measure fat-free mass (FFM). Accordingly, this study is based on data from our recent trial comparing the sensitivity of the main field methods available with that of dual-energy X-ray absorptiometry (DXA) as reference and analyzing the cross-sectional accuracy of these field methods in recreationally resistance-trained males. We hypothesized that the use of these techniques would lead to varying estimates of FFM compared with DXA. Participants (N = 23; 21.4 ± 3.3 years) completed a 10-week resistance training plus diet intervention designed to optimize hypertrophy. FFM was determined by bioelectrical impedance analysis (BIA), 23 anthropometric equations, and DXA. After the intervention, FFM increased significantly according to BIA and most anthropometric estimates, but this increase was not detected by 2 anthropometric equations or by DXA. Only 1 of these 2 equations showed significant correlation with DXA and no standardized or significant differences to this reference method, although it did display significant heteroscedasticity. In our cross-sectional analysis, only 1 anthropometric equation gave rise to good accuracy as confirmed by DXA. Our findings indicate that the use of different techniques to assess FFM gains in response to a hypertrophic intervention yields different results. BIA with general embedded equations should not be used to monitor a young male adult's body composition. To monitor FFM over time, we would recommend the Dunne et al. equation (2) as the most sensitive field method, and to assess FFM cross-sectionally, equation (1) of these authors is the most accurate field method.

Methods over Materials: The Need for Sport-Specific Equations to Accurately Predict Fat Mass Using Bioimpedance Analysis or Anthropometry

Bioelectrical impedance analysis (BIA) and anthropometry are considered alternatives to well-established reference techniques for assessing body composition. In team sports, the percentage of fat mass (FM%) is one of the most informative parameters, and a wide range of predictive equations allow for its estimation through both BIA and anthropometry. Although it is not clear which of these two techniques is more accurate for estimating FM%, the choice of the predictive equation could be a determining factor. The present study aimed to examine the validity of BIA and anthropometry in estimating FM% with different predictive equations, using dual X-ray absorptiometry (DXA) as a reference, in a group of futsal players. A total of 67 high-level male futsal players (age 23.7 ± 5.4 years) underwent BIA, anthropometric measurements, and DXA scanning. Four generalized, four athletic, and two sport-specific predictive equations were used for estimating FM% from raw bioelectric and anthropometric parameters. DXA-derived FM% was used as a reference. BIA-based generalized equations overestimated FM% (ranging from 1.13 to 2.69%, p < 0.05), whereas anthropometry-based generalized equations underestimated FM% in the futsal players (ranging from −1.72 to −2.04%, p < 0.05). Compared to DXA, no mean bias (p > 0.05) was observed using the athletic and sport-specific equations. Sport-specific equations allowed for more accurate and precise FM% estimations than did athletic predictive equations, with no trend (ranging from r = −0.217 to 0.235, p > 0.05). Regardless of the instrument, the choice of the equation determines the validity in FM% prediction. In conclusion, BIA and anthropometry can be used interchangeably, allowing for valid FM% estimations, provided that athletic and sport-specific equations are applied.

Variations in common operations in athletes and non-Athletes

Background

Achieving pre-injury activity level after an injury is the fundamental goal of any orthopedic treatment for an athlete. Unfortunately, pre-injury activity levels differ significantly in different patient categories, especially in athletes and non-athlete. Hence, an outcome suitable to a non-athlete may not be adequate for an athlete. This has led to variations in the surgical approach to the same injury in an athlete and non-athlete.There is plenty of literature published comparing the outcome in athletes and non-athletes after a particular surgery. Scattered discussion about variations in these surgeries based on functional demand was done in many publications. But there was a lack of a comprehensive narrative review summarizing variations in common operations among athletes and non-athletes.

Aim

This review attempted to summarize variations in common sports operations between high functional demand patients and low demand patients and discuss the variations from the author's perspective.

Methods

A review of all the relevant papers were conducted focusing on athletes and non-athletes. Most commonly performed sports surgeries were ACL reconstruction, Meniscal repair, PCL reconstruction, and Shoulder instability surgery. A literature search was done for each commonly performed surgery using relevant keywords in PubMed and Google Scholars. Summary of papers pertinent to athletes and non-athletes were compiled to prepare this narrative review.

Results

There is a lack of papers directly comparing results in athletes and non-athletes. However, many research papers discussed surgical variations in athletes (high demand) and non-athletes (low demand) patients. There are controversies in all commonly performed surgeries, and none of the papers gives a definitive guideline on the approach to athletes and non-athlete.

Conclusion

Rather than a common suggestion on surgical variation, an individualized approach would be appropriate to decide on variation in particular surgery in both athletes and non-athletes.

I expected to be pain free: a qualitative study exploring athletes' expectations and experiences of care received by sports chiropractors

Background

Knowledge about patient satisfaction and experience with care they receive can guide practitioners in establishing doctor-patient relationships and improve health outcomes. Although evidence suggests high patient satisfaction with chiropractic care in general, there is limited understanding of the expectations and experiences of athletes receiving sports chiropractic care.

Objective

To explore the athletes’ expectations and experiences with care received from sports chiropractors, and their perceptions of relevant areas of future research.

Methods

A qualitative study was conducted through an interpretivist lens exploring the perspectives of elite and competitive athletes receiving care from sports chiropractors in Canada. Participants were purposively recruited and interviewed until saturation was reached. Two research team members independently analyzed the interview transcripts using a conventional approach to content analysis. Content was inductively coded and discussed by the research team to generate categories.

Results

We interviewed 18 participants between December 2018 and March 2020, 14 were national level athletes participating in sports ranging from paddling to combat sports. Reported reasons for seeking care included acute care, injury prevention, enhancing performance and maintenance care. Generated categories were organized under topics of experience with care, expectations of care, and research agenda. Participants experienced a variety of interventions, reassurance, varying treatment times, and reported positive impact on their athletic performance. They expected musculoskeletal assessment and treatment including at and beyond the injury site, symptom improvement, good communication and expertise from the chiropractor. Some participants suggested interpersonal and interprofessional communication can be improved, in particular the level of collaboration with other members of their health care team. Overall, participants reported a high level of trust and satisfaction with care received from sports chiropractors. From our participants’ perspective, suggested areas of research should focus on injury mechanics and prevention, impact of care on performance, and interprofessional collaboration.

Conclusions

In general, participants were very satisfied with care. Overall, participants’ expectations and experiences aligned but changed over time. Addressing the findings of this study can be used to enhance the quality of care provided to athletes from sports chiropractors, as well as inform future research agendas. Further work assessing if athletes in other competitive levels have similar experiences and expectations is needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12998-022-00426-4.

Development and Cross-Validation of a Predictive Equation for Fat-Free Mass in Brazilian Adolescents by Bioelectrical Impedance

The bioelectrical impedance analysis (BIA) is one of the most commonly used techniques for assessing body composition in a clinical setting and in field approaches, as it has the advantages of easy application, fast, and non-invasive, in addition to its relatively low cost. However, the available predictive equations need to be valid for the evaluated subjects. The aim of this study was to verify the validity of several published BIA equations in estimating fat-free mass (FFM) among Brazilian adolescents, in addition to developing and cross-validating a BIA equation to estimate FFM appropriate for Brazilian adolescents. This is a cross-sectional study with 257 adolescents (128 girls) aged 10-19 years, randomly divided into two groups, namely, development (n = 172) and cross-validation (n = 85). The standard technique for assessing FFM was dual X-ray absorptiometry (DXA). The paired t-test, multiple regression, and the Bland-Altman plots were used to test the validity of the proposed models and to perform cross-validation of the model. The equation derived in this study was as follows: FFM = -17.189 + 0.498 (Height2/Resistance) + 0.226 Weight + 0.071 Reactance - 2.378 Sex + 0.097 Height + 0.222 Age; r 2 = 0.92; standard error of the estimate = 2.49 kg; the new equation for FFM showed better agreement when compared with that of the equations developed in other countries. In conclusion, the newly developed equations provide a valid FFM estimation and are recommended for Brazilian adolescents with similar characteristics.

Reference Percentiles for Bioelectrical Phase Angle in Athletes

The present study aimed to develop reference values for bioelectrical phase angle in male and female athletes from different sports. Overall, 2224 subjects participated in this study [1658 males (age 26.2 ± 8.9 y) and 566 females (age 26.9 ± 6.6 y)]. Participants were categorized by their sport discipline and sorted into three different sport modalities: endurance, velocity/power, and team sports. Phase angle was directly measured using a foot-to-hand bioimpedance technology at a 50 kHz frequency during the in-season period. Reference percentiles (5th, 15th, 50th, 85th, and 95th) were calculated and stratified by sex, sport discipline and modality using an empirical Bayesian analysis. This method allows for the sharing of information between different groups, creating reference percentiles, even for sports disciplines with few observations. Phase angle differed (men: p < 0.001; women: p = 0.003) among the three sport modalities, where endurance athletes showed a lower value than the other groups (men: vs. velocity/power: p = 0.010, 95% CI = -0.43 to -0.04; vs. team sports: p < 0.001, 95% CI = -0.48 to -0.02; women: vs. velocity/power: p = 0.002, 95% CI = -0.59 to -0.10; vs. team sports: p = 0.015, 95% CI = -0.52 to -0.04). Male athletes showed a higher phase angle than female athletes within each sport modality (endurance: p < 0.01, 95% CI = 0.63 to 1.14; velocity/power: p < 0.01, 95% CI = 0.68 to 1.07; team sports: p < 0.01, 95% CI = 0.98 to 1.23). We derived phase angle reference percentiles for endurance, velocity/power, and team sports athletes. Additionally, we calculated sex-specific references for a total of 22 and 19 sport disciplines for male and female athletes, respectively. This study provides sex- and sport-specific percentiles for phase angle that can track body composition and performance-related parameters in athletes.