Cited by 16Body Composition Measurement TechniquesSports Performance and TrainingElectrical and Bioimpedance Tomography

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

Open access
Campa, Francesco, Bongiovanni, Tindaro, Rossi, Alessio, Cerullo, Giuseppe, Casolo, Andrea, Martera, Giulia, Trecroci, Athos, Moro, Tatiana +1 more·2023·Journal of Translational Medicine

Abstract

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) + (stature 2/R × 0.227) + (Xc × 0.086) + (age × 0.058), R 2 = 0.97, Standard error of estimation (SEE) = 1.0 kg; LST = − 8.929 + (body mass × 0.635) + (stature 2/R × 0.244) + (Xc × 0.093) + (age × 0.048), R 2 = 0.96, SEE = 0.9 kg; ALST = − 24.068 + (body mass × 0.347) + (stature 2/R × 0.308) + (Xc × 0.152), R 2 = 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 R 2 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.

AI snapshot

Written from the paper’s full text.

TL;DR

New soccer-specific BIA equations were developed and validated in 102 male elite Italian Serie A soccer players to estimate fat-free mass (FFM), lean soft tissue (LST), and appendicular lean soft tissue (ALST). The new models showed high accuracy and no mean bias, whereas generalized athletic BIA equations underestimated FFM components.

Key findings

  • Developed models: FFM = −7.729 + (body mass × 0.686) + (stature²/R × 0.227) + (Xc × 0.086) + (age × 0.058), R² = 0.97, 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.
  • In train-test validation, generalized formulas for athletes underestimated all predicted FFM components (p < 0.01), while the new soccer-specific models showed no mean bias (p > 0.05), with R² values ranging from 0.83 to 0.91 and no trend (p > 0.05).
  • RROC AUC scores were 0.92 for FFM, 0.92 for LST, and 0.74 for ALST.
  • Using the new FFM model, predicted vs reference fat mass percentage showed no mean difference (12.3% ± 0.8; P = 0.954), whereas the generalized athletic equation overestimated fat mass percentage (15.6% ± 1.3; P < 0.001).

Methods

  • Cross-sectional study of 102 male elite soccer players (mean age 24.7 ± 5.7 years) from the Italian first division (Serie A), assessed during the first half of the in-season period and randomly divided into development (N = 73) and validation (N = 29) groups.
  • Foot-to-hand BIA at 50 kHz measured resistance (R) and reactance (Xc); DXA provided reference FFM, LST, and ALST.
  • Backward stepwise linear regression developed models; validation used regression analysis, Bland–Altman tests, concordance correlation coefficient, and RROC AUC.

Limitations

  • The paper states DXA is not the state-of-the-art method for fat and FFM, which should be assessed with air plethysmography and dilution techniques in a four-compartment model.
  • The cross-sectional design prevents assessing predicted FFM components over time; longitudinal and interventional studies are needed.
  • Findings cannot be generalized to other sports, females, sub-elite or adolescent players, or BIA measures from different technologies or sampling frequencies.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1186/s12967-023-04795-z

Cites

53 of 53 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

19 of 50 cited sources checked · 8 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    The use of predictive equations developed in the general population results in an underestimation of FFM components when applied to athletes.

    “Particularly, the use of predictive equations developed in the general population results in an underestimation of FFM components when applied to athletes [22].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [22] Coratella G, Campa F, Matias CN, Toselli S, Koury JC, Andreoli A, et al. Generalized bioelectric impedance-based equations underestimate body fluids in athletes. Scand J Med Sci Sports. 2021. https://doi.org/10.1111/sms.14033. source

      The Discussion (page unavailable) reports that generalized equations generally underestimated total body water and extracellular water in athletes. These are FFM components, but the paper does not establish underestimation of FFM components more broadly, and it reports exceptions for some equations and athlete groups. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    Soccer players present different bioelectrical characteristics compared to other athletes.

    “As result of these peculiarities, recent studies [24, 27] have shown that soccer players present different bioelectrical characteristics compared to other athletes [28] and this could make it necessary to develop dedicated predictive equations.”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [24] Mala L, Maly T, Zahalka F, Bunc V, Kaplan A, Jebavy R, et al. Body composition of elite female players in five different sports games. J Hum Kinet. 2015;45:207–15. https://doi.org/10.1515/hukin-2015-0021. source

      The Conclusion (page unavailable) reports that elite female soccer players differed from players of at least one other sport in 8 of 10 body-composition variables measured using bioimpedance. It does not establish that soccer players generally have different bioelectrical characteristics: the measured phase angle did not differ significantly between groups, and the study does not report a comparison of raw electrical characteristics. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [27] Campa F, Silva AM, Talluri J, Matias CN, Badicu G, Toselli S. Somatotype and bioimpedance vector analysis: a new target zone for male athletes. Sustainability. 2020. https://doi.org/10.3390/su12114365. source
    • cites [28] Santos DA. Reference values for body composition and anthropometric measurements in athletes. PLoS ONE. 2014. https://doi.org/10.1371/journal.pone.0097846. source

      The Results tables (page not available) compare soccer players with athletes in other sports on body-composition and anthropometric measures. The Methods list weight, height, anthropometry and DXA, but the passages found when searching for bioelectrical impedance, resistance, reactance and phase angle do not address whether soccer players differ in bioelectrical characteristics. (LLM, conf=0.76)

      Experimental — accuracy not yet measured
  • Premisecitation

    Loss of accuracy of BIA predictive equations may occur when anthropometric characteristics differ between the development study subjects and the subjects on whom the formulas are applied.

    “This loss of accuracy may happen when anthropometric characteristics differ among the subjects involved in the development studies and the subjects on which these formulas are applied [11].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [11] Campa F, Coratella G. Athlete or non-athlete? This is the question in body composition. Front Physiol. 2021. https://doi.org/10.3389/fphys.2021.814572. source
  • Premisecitation

    Underestimation of FFM components from generalized equations was already shown when equations for the normal population were applied to athletes.

    “The underestimation of FFM components from generalized equations was already showed when equations for the normal population were applied on athletes [22].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [22] Coratella G, Campa F, Matias CN, Toselli S, Koury JC, Andreoli A, et al. Generalized bioelectric impedance-based equations underestimate body fluids in athletes. Scand J Med Sci Sports. 2021. https://doi.org/10.1111/sms.14033. source
  • Premisecitation

    Lean soft tissues are more sensitive to variations due to detraining periods where a rapid decrease can be experimented.

    “but with respect to body fat, lean soft tissues are more sensitive to variations due to detraining periods where a rapid decrease can be experimented [50].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [50] Campa F, Bongiovanni T, Trecroci A, Rossi A, Greco G, Pasta G, et al. Effects of the COVID-19 lockdown on body composition and bioelectrical phase angle in serie A Soccer players: a comparison of two consecutive seasons. Biology. 2021. https://doi.org/10.3390/biology10111175. source

      The Discussion (page unavailable) reports that muscle mass fell markedly during the detraining-like lockdown while fat-mass percentage remained unchanged. This supports the comparison for muscle mass in the soccer players studied, but the paper does not establish that lean soft tissues generally decrease rapidly during detraining. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 21
  • May combine two claims. 17
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    The resistance index being the second predictor is due to the conductive properties of soft tissues.

    “this is the result of the well-known conductive properties of soft tissues [5]”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [5] Lukaski H, Raymond-Pope CJ. New frontiers of body composition in sport. Int J Sports Med. 2021. https://doi.org/10.1055/a-1373-5881. source
  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisecitation

    It is crucial to use BIA-based equations that have been developed and validated in a similar population as the one being assessed.

    “Recent studies showed that it is crucial to use BIA-based equations that have been developed and validated in a similar population as the one being assessed [20, 21].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [20] Moon JR. Body composition in athletes and sports nutrition: an examination of the bioimpedance analysis technique. Eur J Clin Nutr. 2013;67:S54. https://doi.org/10.1038/ejcn.2012.165. source
    • cites [21] Campa F, Matias CN, Moro T, Cerullo G, Casolo A, Teixeira FJ, et al. Methods over materials: the need for sport-specific equations to accurately predict fat mass using bioimpedance analysis or anthropometry. Nutrients. 2023. https://doi.org/10.3390/nu15020278. source
  • May combine two claims.

    Premisecitation

    Soccer players are on average shorter and lighter than volleyball or basketball players, resulting in lower FFM and different morphology.

    “For example, soccer players are on average shorter and lighter than volleyball or basketball players, resulting in a lower FFM as well as a different morphology [24, 25].”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [24] Mala L, Maly T, Zahalka F, Bunc V, Kaplan A, Jebavy R, et al. Body composition of elite female players in five different sports games. J Hum Kinet. 2015;45:207–15. https://doi.org/10.1515/hukin-2015-0021. source

      The Discussion reports that elite female soccer players had significantly lower fat-free mass than volleyball and basketball players, and links that difference to their lower height and body mass. The Results also report height and body-mass differences between those groups. The claim generalizes beyond elite female players and presents the proposed explanation as a definite cause, whereas the paper says the differences could be caused by height. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [25] Campa F, Silva AM, Matias CN, Monteiro CP, Paoli A, Nunes JP, et al. Body water content and morphological characteristics modify bioimpedance vector patterns in volleyball, soccer, and rugby players. Int J Environ Res Public Health. 2020. https://doi.org/10.3390/ijerph17186604. source

      The Results report different mean somatotype components for soccer and volleyball players, offering some support for a difference in morphology. Our copy does not report that soccer players were shorter or lighter, or had lower fat-free mass, than volleyball players; the study did not include basketball players. (LLM, conf=0.81)

      Experimental — accuracy not yet measured
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Interpretationcitation

    ALST reduction could be expected during transition periods and therefore closely monitored in soccer players.

    “Regarding the ALST, its reduction could be expected during transition periods and therefore closely monitored in soccer players [50].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [50] Campa F, Bongiovanni T, Trecroci A, Rossi A, Greco G, Pasta G, et al. Effects of the COVID-19 lockdown on body composition and bioelectrical phase angle in serie A Soccer players: a comparison of two consecutive seasons. Biology. 2021. https://doi.org/10.3390/biology10111175. source

      The Abstract and Conclusions report reduced muscle mass during the lockdown-related detraining period and recommend monitoring muscle mass in soccer players during detraining. The Introduction also discusses body-composition changes during off-season breaks. However, the study measured estimated muscle mass, not ALST specifically, and did not directly test ordinary transition periods. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    BIVA provides soft tissue classification (under, normal, over) and ranking (more or less than before intervention) by comparing an individual vector to a reference population.

    “the characteristic and innovative aspect of BIVA is that it provides soft tissue classification (under, normal, and over) and ranking (more or less than before intervention), comparing the position of an individual vector to a reference population [5].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [5] Lukaski H, Raymond-Pope CJ. New frontiers of body composition in sport. Int J Sports Med. 2021. https://doi.org/10.1055/a-1373-5881. source
  • May combine two claims.

    Findingcitation

    The participants of the present study had higher FFM and ALST values than previous groups, in line with previous studies on soccer players.

    “In contrast, the participants of the present study had higher FFM and ALST values, which are in line with previous studies on soccer players [29, 43].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [29] Micheli ML, Pagani L, Marella M, Gulisano M, Piccoli A, Angelini F, et al. Bioimpedance and impedance vector patterns as predictors of league level in male soccer players. Int J Sports Physiol Perform. 2014;9:532–9. https://doi.org/10.1123/ijspp.2013-0119. source
    • cites [43] Bongiovanni T, Tinsley G, Martera G, Orlandi C, Genovesi F, Puleo G, et al. Regional lean soft tissue and intracellular water are associated with changes in lower-body neuromuscular performance: a pilot study in elite soccer players. Eur J Investig Heal Psychol Educ. 2022;12:882–92. https://doi.org/10.3390/ejihpe12080064. source
  • May combine two claims.

    Study design and conductcitation

    The present findings cannot be generalized to other sport disciplines, females, sub-elite or adolescent players, and cannot be extended to BIA measures from different technologies or sampling frequencies due to lack of agreement between bioelectrical impedance analysers.

    “Lastly, the present findings cannot be generalized to other sport disciplines, females, sub-elite or adolescent players, and they cannot be extended to BIA-measures obtained from different technologies or sampling frequencies due to the lack of agreement between bioelectrical impedance analysers [53, 54].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [53] Dellinger JR, Johnson BA, Benavides ML, Moore ML, Stratton MT, Harty PS, et al. Agreement of bioelectrical resistance, reactance, and phase angle values from supine and standing bioimpedance analyzers. Physiol Meas. 2021. https://doi.org/10.1088/1361-6579/abe6fa. source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [54] Stratton MT, Smith RW, Harty PS, Rodriguez C, Johnson BA, Dellinger JR, et al. Longitudinal agreement of four bioimpedance analyzers for detecting changes in raw bioimpedance during purposeful weight gain with resistance training. Eur J Clin Nutr. 2021;75:1060–8. https://doi.org/10.1038/s41430-020-00811-3. source
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Professional soccer players present fat mass values ranging from 11 to 14%, depending on the assessment method.

    “Professional soccer players present fat mass values ranging from 11 to 14%, depending on the assessment method [19].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [19] Sebastiá-Rico J, Soriano JM, González-Gálvez N, Martínez-Sanz JM. Body composition of male professional soccer players using different measurement methods: a systematic review and meta-analysis. Nutrients. 2023. https://doi.org/10.3390/nu15051160. source

      The Results report an overall mean fat-mass percentage of 11.85%, and the Discussion reports a DXA mean of 13.46%; both fall within the claimed range. But the Results also report a 10.19% mean for anthropometric equations, so 11–14% does not capture the full method-dependent range reported for male professional players. Page numbers are unavailable in our copy. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Recent studies highlighted that body composition differs according to gender, competitive levels, and age groups rather than playing position in soccer players.

    “Indeed, recent studies highlighted how body composition differs according to gender, competitive levels, and age groups rather than the playing position in soccer players [44, 45].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [44] Slimani M, Nikolaidis PT. Anthropometric and physiological characteristics of male soccer players according to their competitive level, playing position and age group: a systematic review. J Sports Med Phys Fitness. 2019;59:141–63. https://doi.org/10.23736/S0022-4707.17.07950-6. source
    • cites [45] Mascherini G, Castizo-Olier J, Irurtia A, Petri C, Galanti G. Differences between the sexes in athletes’ body composition and lower limb bioimpedance values. Muscles Ligaments Tendons J. 2017;7:573–81. https://doi.org/10.11138/mltj/2017.7.4.573. source

      The Discussion reports differences in body composition between male and female elite soccer players. The Methods and Discussion indicate that players were matched by age and competed at the same elite level; the paper does not establish differences by age group or competitive level, or compare those factors with playing position. (LLM, conf=0.89)

      Experimental — accuracy not yet measured
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingcitation

    Anthropometric dimensions of elite soccer players revealed a profile characterized by high musculoskeletal and loglinear components, with a low percentage of body fat.

    “In line with previous studies, anthropometric dimensions of elite soccer players revealed a profile characterized by high musculoskeletal as well as loglinear components, with a low percentage of body fat [25, 44].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [25] Campa F, Silva AM, Matias CN, Monteiro CP, Paoli A, Nunes JP, et al. Body water content and morphological characteristics modify bioimpedance vector patterns in volleyball, soccer, and rugby players. Int J Environ Res Public Health. 2020. https://doi.org/10.3390/ijerph17186604. source

      The Results report that the soccer players’ average somatotype was ectomorphic mesomorph, with relatively high mesomorphy and ectomorphy and low endomorphy. This supports the muscular and linear profile, but the paper does not report a body-fat percentage for the soccer players; low endomorphy alone does not establish that part of the claim. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [44] Slimani M, Nikolaidis PT. Anthropometric and physiological characteristics of male soccer players according to their competitive level, playing position and age group: a systematic review. J Sports Med Phys Fitness. 2019;59:141–63. https://doi.org/10.23736/S0022-4707.17.07950-6. source
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingcitation

    Somatotype was assessed among participants and three morphologies (balanced mesomorph, ectomorphic mesomorph, and mesomorph-ectomorph) were identified according to the Heath and Carter method.

    “Somatotype was also assessed among the participants and three different morphologies (i.e., balanced mesomorph, ectomorphic mesomorph, and mesomorph-ectomorph) were identified according to the Heath and Carter method [34].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [34] Carter JEL. The heath-carter anthropometric somatotype. San Diego: San Diego State University; 2002.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    Individual bioimpedance vectors were distributed within the BIVA soccer-specific references, with some vectors positioned out of the 95% tolerance ellipse.

    “Considering the individual vectors, they were distributed within the BIVA soccer-specific references [29], with some vectors positioned out of the 95% tolerance ellipse.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [29] Micheli ML, Pagani L, Marella M, Gulisano M, Piccoli A, Angelini F, et al. Bioimpedance and impedance vector patterns as predictors of league level in male soccer players. Int J Sports Physiol Perform. 2014;9:532–9. https://doi.org/10.1123/ijspp.2013-0119. source
  • May combine two claims.

    Findingown data

    The use of a generalized equation [33] resulted in an underestimation of FFM and then in an overestimation of fat mass in the soccer players.

    “Indeed, the use of a generalized equation [33] resulted in an underestimation of FFM and then in an overestimation of the fat mass in the soccer players.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [33] Matias CN, Campa F, Santos DA, Lukaski H, Sardinha LB, Silva AM. Fat-free mass bioelectrical impedance analysis predictive equation for athletes using a 4-compartment model. Int J Sports Med. 2021;42:27–32. https://doi.org/10.1055/a-1179-6236. source
  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Urine-specific gravity ≤ 1.020 was used to assure that participants were in a hydrated state.

    “Urine-specific gravity has been determined to assure that participants were in a hydrated state, defined as the value of urine-specific gravity ≤ 1.020 [36].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [36] Armstrong LE. Assessing hydration status: the elusive gold standard. J Am Coll Nutr. 2007;26:575S-584S. source
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The DXA scanner was calibrated daily prior to scanning using a calibration block according to manufacturer indications.

    “The scanner was calibrated daily prior to scanning, according to manufacturer indications using a calibration block.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    Two-thirds of participants were randomly assigned to the train set and one-third to the test group.

    “2/3 of the participants were randomly assigned (using random.org) to the train set, while the remaining participants (1/3) to the test group.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim.

    Study design and conductnone given

    A sample size of 77 participants was calculated considering a type 1 error of 5% and a power of 80%.

    “Given that a sample size of 77 participants was calculated considering a type 1 error of 5% and a power of 80%”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationown data

    The newly developed soccer-specific formulas enable valid estimations of body composition while preserving the portability of a field-based method.

    “The newly developed soccer-specific formulas enable valid estimations of body composition while preserving the portability of a field-based method.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: DXA provides accurate reference measurements of FFM, LST, and ALST.
    • Rests on an assumption: The sample of Italian Serie A male soccer players is representative of male elite soccer players generally.
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Normality of residuals and homogeneity of variance were tested during model development.

    “During model development, normality of residuals and homogeneity of variance were tested.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The test-retest coefficient of variation on duplicate measurements of R and Xc was 0.3% and 0.9%, respectively.

    “The precision of the bioelectrical device was assessed before each test session; the test– retest coefficient of variation (CV% = standard deviation/mean × 100%) on duplicate measurements of R and Xc was 0.3% and 0.9%, respectively.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationown data

    The applicability of the new equations may extend to elite soccer players worldwide, given that participants originated from diverse territories reflecting the typical composition of high-level soccer teams.

    “Conversely, the applicability of the new equations may extend to elite soccer players worldwide, given that the participants in this study originated from diverse territories, reflecting the typical composition of high-level soccer teams.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationcitation

    Underestimation of FFM may result in a hypoproteic diet and impairment of maintenance of skeletal muscle structures, given that athletes are commonly advised to consume protein intakes of ∼2.3-3.1 g per kg of FFM during the preparatory phase.

    “Considering that during the preparatory phase athletes are commonly advised to consume protein intakes in the range of ∼2.3–3.1 g for each kg of FFM, its underestimation may result in a hypoproteic diet and in an impairment of the maintenance of the skeletal muscle structures [12].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [12] Murphy CH, Hector AJ, Phillips SM. Considerations for protein intake in managing weight loss in athletes. Eur J Sport Sci. 2015;15:21–8. https://doi.org/10.1080/17461391.2014.936325. source
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Vectors out of the 95% tolerance ellipse may represent subjects with a lower fluid content with respect to the average soccer population.

    “According to the BIVA basics, such as vectors may represent subjects with a lower fluid content with respect to the average soccer population.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    DXA is not considered the state-of-the-art method for evaluating fat and FFM; it should be employed with air plethysmography and dilution techniques according to a four-compartment body composition model.

    “although DXA represents one of the most accurate technique for assessing lean soft tissues it is not considered the state-of-the-art method for evaluating fat and FFM, for which it should be employed in conjunction with air plethysmography and dilution techniques according to a four-compartment body composition model [14].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] Silva AM. Structural and functional body components in athletic health and performance phenotypes. Eur J Clin Nutr. 2019;73:215–24. https://doi.org/10.1038/s41430-018-0321-9. source
    • Rests on an assumption: DXA is one of the most accurate techniques for assessing lean soft tissues.
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    A low total body water may depend on a low body mass, so long vectors should not always be related to a hypohydration state.

    “Since a low total body water may depend by a low body mass, long vectors should not be always related to a hypohydration state.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    The independence of morphologic characteristics from positions may reflect the profile of the new millennium soccer player, where body dimensions can be similar among roles.

    “and this may reflect the profile of the new millennium soccer player, where body dimensions can be similar among roles.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning

    The new equations allow managing training and nutritional strategies aiming to enhance body composition and soccer performance, while maintaining the portability of BIA.

    “This allows to manage training and nutritional strategies aiming to enhance body composition and soccer performance, while maintaining the portability of the BIA.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    These groups of athletes presented average values of 47.7 kg for FFM and 29.4 kg for ALST.

    “These groups of athletes presented average values of 47.7 kg and 29.4 kg for FFM [33] and ALST [32], respectively.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [33] Matias CN, Campa F, Santos DA, Lukaski H, Sardinha LB, Silva AM. Fat-free mass bioelectrical impedance analysis predictive equation for athletes using a 4-compartment model. Int J Sports Med. 2021;42:27–32. https://doi.org/10.1055/a-1179-6236. source
    • cites [32] Sardinha LB, Correia IR, Magalhães JP, Júdice PB, Silva AM, Hetherington-Rauth M. Development and validation of BIA prediction equations of upper and lower limb lean soft tissue in athletes. Eur J Clin Nutr. 2020;74:1646–52. https://doi.org/10.1038/s41430-020-0666-8. source
  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationcitation

    Valid estimations of LST and ALST can be useful for monitoring the response of training regimes across the different phases of the season or during return-to-play after an injury.

    “Therefore, valid estimations of LST and ALST can be useful for monitor the response of training regimes across the different phases of the season or during the return-to-play after an injury [52].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [52] Nescolarde L, Yanguas J, Lukaski H, Rodas G, Rosell-Ferrer J. Localized BIA identifies structural and pathophysiological changes in soft tissue after post-traumatic injuries in soccer players. Annu Int Conf IEEE Eng Med Biol Soc. 2014;2014:3743–6. https://doi.org/10.1109/EMBC.2014.6944437. source
29 of 29
  • The paper relies on this without support.

    DXA provides accurate reference measurements of FFM, LST, and ALST.

    “DXA was performed to derive whole-body measures of FFM, fat mass, LST, and ALST.”
  • The paper relies on this without support.

    The sample of Italian Serie A male soccer players is representative of male elite soccer players generally.

    “A total of 102 male soccer players (age 24.7 ± 5.7 yrs) from the first Italian division (Serie A) were included in this cross-sectional study.”
    “The utilization of generalized predictive equations leads to an underestimation of FFM and ALST in elite soccer players.”
  • The paper relies on this without support.

    No other study has validated BIA prediction equations for estimating FFM components in soccer players.

    “no other study has validated BIA prediction equations for estimating FFM components in soccer players.”
  • The paper relies on this without support.

    DXA is one of the most accurate techniques for assessing lean soft tissues.

    “although DXA represents one of the most accurate technique for assessing lean soft tissues”
  • The paper relies on this without support.

    There are currently no specific reference values for elite soccer players.

    “To our knowledge, there are currently no specific reference values ​​for elite soccer players”
5 of 5

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Body-mass VIF changes between models with identical predictors

    Minor

    The FFM and LST models use the same development group and the same four predictors. A predictor's variance inflation factor does not depend on the outcome, so body mass cannot have VIFs of both 1.48 and 3.42.

  • Negative ALST limit is labeled underestimation despite the stated sign convention

    Minor

    The paragraph associates a negative lower limit of agreement for ALST (−11.3 kg) with overestimation, but calls its negative upper limit (−6.1 kg) underestimation. Under the sign convention used for the lower limit, the upper limit also indicates overestimation, contradicting the conclusion about ALST at higher values.

  • Overall mean age is below both subgroup means

    Minor

    The abstract reports a mean age of 24.7 years, but the development and validation groups are the entire sample and have mean ages of 25.2 and 25.9 years. The overall mean cannot be lower than both subgroup means.

  • Individual vectors cannot be both within 50% and outside 95% ellipses

    Minor

    The discussion says individual vectors fell within the 50% reference tolerance ellipse, then says some individual vectors were outside the 95% tolerance ellipse. Vectors inside the 50% ellipse cannot also be outside the wider 95% ellipse.

  • Lean-soft-tissue SEE differs between prose and table

    Minor

    The prose gives the LST model's SEE as 0.9 kg, while Table 2 gives 0.99 kg. Rounded to one decimal place, 0.99 kg is 1.0 kg, not 0.9 kg.

5 of 5

Cites

Flagged first, then by citations

Cited by

Sorted by citations

Authors
Campa, F., Bongiovanni, T., Rossi, A., Cerullo, G., Casolo, A., Martera, G., Trecroci, A., Moro, T., & Paoli, A.
Affiliations
  • University of Padua (IT)
  • University of Bologna (IT)
  • University of Pisa (IT)
  • University of Milan (IT)
Corresponding author
Casolo, Andrea
Venue
Journal of Translational Medicine
Published
2023-12-15
Volume
21
Issue
1
Pages
912-912
ISSN
1479-5876 (ISSN-L)
OpenAlex
W4389788180
Cited by
16
References
53
Citations by year
2026: 4 · 2025: 4 · 2024: 7
FWCI
2.36
Type
journal article
Language
en
Open access
Locations
  • Journal of Translational Medicine (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, cc-by)
  • Padua Research Archive (University of Padova) (submittedVersion, cc-by)
  • Archivio Istituzionale della Ricerca (Universita Degli Studi Di Milano) (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Università degli Studi di Padova
Topics
  • Health Sciences › Medicine › Physiology › Body Composition Measurement Techniques
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Electrical and Bioimpedance Tomography
Keywords
bioelectrical impedance analysis, fat-free mass, soccer players, prediction equations, body composition, bioimpedance, reactance, resistance
MeSH terms
Adult, Body Composition, Humans, Male, Regression Analysis, Soccer, Reproducibility of Results

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-07.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-07.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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