Association between phase angle and isolated and grouped physical fitness indicators in adolescents

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Association Between Phase Angle And Isolated And Grouped Physical Fitness Indicators In Adolescents ´ Priscila Custodio Martins , Luiz Rodrigo Augustemak de Lima , ´ Juliane Berria , Edio Luiz Petroski , Analiza Monica Silva , Diego Augusto Santos Silva PII: DOI: Reference:

S0031-9384(19)31358-7 https://doi.org/10.1016/j.physbeh.2020.112825 PHB 112825

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Physiology & Behavior

Received date: Revised date: Accepted date:

18 December 2019 23 January 2020 25 January 2020

´ Please cite this article as: Priscila Custodio Martins , Luiz Rodrigo Augustemak de Lima , ´ Juliane Berria , Edio Luiz Petroski , Analiza Monica Silva , Diego Augusto Santos Silva , Association Between Phase Angle And Isolated And Grouped Physical Fitness Indicators In Adolescents, Physiology & Behavior (2020), doi: https://doi.org/10.1016/j.physbeh.2020.112825

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1 Highlights  Phase angle was directly associated with isolated and grouped physical fitness indicators in adolescents;  The phase angle values can vary according to physical fitness, which indicates the use of phase angle as a marker that presents variability depending on the level of physical fitness of adolescentes;  The phase angle is as a useful tool to be used in physical assessments and screening of recommendations for physical activity, physical exercise, and health-related physical fitness.

2 Title: ASSOCIATION BETWEEN PHASE ANGLE AND ISOLATED AND GROUPED PHYSICAL FITNESS INDICATORS IN ADOLESCENTS

Running title: PHASE ANGLE AND PHYSICAL FITNESS

Priscila Custódio Martins¹, Luiz Rodrigo Augustemak de Lima², Juliane Berria³, Edio Luiz Petroski³, Analiza Mónica Silva4, Diego Augusto Santos Silva³

¹Degree in Physical Education. Federal University of Santa Catarina. Research Center in Kinanthropometry and Human Performance. Florianópolis, Brazil. ²Professor, PhD. State University Alagoas, Maceio, Brazil. ³Professor, PhD. Research Center in Kinanthropometry and Human Performance. Florianópolis, Brazil. 4

Professor, PhD. Technical University of Lisbon, Faculty of Human Movement, Lisboa, Portugal.

Corresponding author: Priscila Custódio Martins Federal University of Santa Catarina, Sports Center University campus, Trindade Zip code: 88040-900, Florianópolis, Brazil E-mail: [email protected]

Acknowledgements The authors would like to thank all the students that in the study and the staff of the Board of Education of Florianopolis for their contribution to the research. Financial Support This study is financially supported by the National Council for Scientific and Technological Development (CNpQ - 474184/2013-7). PCM received scholarships from the Brazilian Coordination for the Improvement of Higher Education Personnel (CAPES). This study is registered at www.clinicaltrials.gov (Identifier NCT02719704).

3

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical Standards Disclosure

All procedures were approved by the Ethics Committee on Human Research of the Carmela Dutra Maternity Hospital (process 780.303), and all participants provided a consent form signed by their respective legal guardians.

ABSTRACT

Objective: Examine association between phase angle and isolated and grouped physical fitness indicators in adolescents. Methods The sample consisted of 353 adolescents, aged 10-16 years. Phase angle was calculated based on crude resistance and reactance values (50kHz frequency) obtained by tetrapole electrical bioimpedance (BIA). Fat mass and lean mass were estimated by means of anthropometric equations. Hydraulic dynamometer was used to measure handgrip strength and aerobic fitness was obtained by means of the 20-meter back-and-forth test. The z-score for isolated and grouped physical fitness indicators was calculated. Covariates were age, habitual physical activity and screen time (obtained by questionnaire), and sexual maturation (self-reported). Results: For males, phase angle was directly associated with lean mass (β=0.02, p<0.01), handgrip strength (β=0.03, p<0.01), and aerobic fitness (β=0.01, p=0.05), even adjusting for covariates. For females, phase angle was directly associated with lean mass (β=0.02; p=0.04) after adjusting for covariates. Phase angle was directly associated with composite physical fitness z-score in both sexes (male, β=0.09, p<0.01, female, β=0.03, p=0.05), even adjusting for covariates. Conclusions:

4 Phase angle was directly associated with isolated and grouped physical fitness indicators in adolescents. In this way, the phase angle can be used to monitor the health of adolescents.

Keywords: adolescent health, cell membrane, body composition, physical fitness, cardiorespiratory fitness.

INTRODUCTION The phase angle from the relationship between resistance and reactance, data obtained by electrical bioimpedance (BIA) is a marker of nutritional status, prognosis of diseases and health and cell integrity indicator(22), which has been considered as an important tool in the evaluation and prescription of physical exercisesb(26). Probably, part of the growing interest in the phase angle is due to the ease of obtaining data, low cost, and wide possibility of investigation(17). Phase-angle studies have been carried out in different populations, such as in children and adolescents with pathologies(32), healthy adults(25), older adults(29) and athletes (Matias et al., 2015). In summary, phase angle is directly associated with muscle mass and body cell mass in children with type I diabetes(32) and increased strength, endurance, and muscle power in adults (25). In the elderly, phase angle presented an inverse relationship with inflammatory markers (interleukin-6 and TNF-α)(29), and in athletes, phase angle decreased during the competition cycle due to the loss of water and muscle mass(24). Furthermore, a meta-analysis identified that phase angle was directly associated with physical activity in adults with and without the diagnosis of diseases (21). Thus, important changes from cellular to tissue level, as well in the physical function were able to explain the phase angle variability and demonstrate its importance for health. Specifically on physical fitness indicators, previous studies have demonstrated direct association with handgrip strength and fat-free mass in cancer and HIV patients, and in children after congenital heart disease surgery(18,

22)

, in addition to inverse associations with body fat in

5 children and adults(5). Thus, much of the current literature refers to adults or individuals with morphological and metabolic alterations due to the presence of diseases. Since adolescence is marked by major changes in physical fitness due to growth and development(23), the associations reported between physical fitness and phase angle may be different, as the presence of diseases can have consequences that influence the hydration status of tissues, which can influence the direction and magnitude of associations. In addition, no study tested the association between phase angle and combined physical fitness indicators. The combination of physical fitness indicators can compensate for the variability of individual indicators (3)

which can incorporate the deficit values of individual physical fitness indicators, which may

occur simultaneously in adolescents (9). Considering that physical fitness is an important general health(23) understanding the association of isolated and grouped physical fitness indicators and phase angle values may contribute to understand the interrelation between morphology and function, in view of the quality and integrity of body cells and membranes. Therefore, the aim of this study was to analyze the association between phase angle and physical fitness, characterized by isolated and grouped body composition indicators (lean mass and fat mass), handgrip strength, abdominal resistance and aerobic fitness of adolescents. The hypothesis of the study is that the phase angle is associated with greater intensity to the indicator of grouped physical fitness compared to the isolated indicators of physical fitness.

METHODS

Study Design This is a cross-sectional study characterized by a secondary analysis of baseline data from intervention, whose aim was to verify the effect of a multi-component intervention on physical

6 fitness related to health and body image of adolescents(20). The study was conducted in 2015. All parents/guardians signed the informed consent form (TCLE) authorizing participation in the survey and adolescents signed the Assent Term.

Population and sample The target population was adolescents of both sexes aged 10-16 years enrolled in grades 6-9 of elementary school in the municipal school network of Florianopolis, Santa Catarina, Brazil (N = 7,484 students), distributed in 26 schools. Recruitment was carried out on the basis of five schools that met the intervention criteria. At two selected schools, 1011 adolescents were invited to participate in the study. Of this amount, 568 adolescents accepted to participate in the research and returned the TCLE signed by parents/guardians. The final sample consisted of 353 adolescents who performed all baseline assessments. The inclusion criteria were: 1) to present TCLE signed by parents/guardians and 2) to present all evaluations. Exclusion criteria were: 1) to present some motor limitation or musculoskeletal injury that would prevent physical fitness assessments or participate in physical activities offered in interventions; 2) perform nutritional monitoring and / or be taking medications to reduce or increase body mass; 3) not complying with BIA pre-test recommendations. The statistical power for this study was calculated a posteriori to identify associations between phase angle and the isolated and grouped physical fitness indicators, assuming the sample of 353 adolescents, type I (α = 0.05) and type II errors ( β = 0.80) and large effect size of 0.70 (G * Power® software version 3.1.9.2 (Universitat Dusselfodorf, Germany) was used.

Dependent variable

7 Phase angle Phase angle was analyzed using mono-frequency (50 kHz) tetrapole electrical bioimpedance (BIA), Biodinamics apparatus, model BF-310 (TBW/ACT Medical Group, São Paulo, Brazil). BIA was used to measure resistance (R) and reactance (Xc) to calculate the phase angle by the formula: arc tangent (Xc/R) × 180 °/π

(Norman et al., 2012) BIA presents high reproducibility with

concordance coefficient of 0.95-0.99(14). For the evaluation, adolescents remained in supine position on surface non-conductive of electricity. Electrodes were positioned on the dorsal surface of the wrist (proximal sensory electrodes) and ankle (distal source electrodes) at the base of the metacarpophalangeal and mactatarsophalangeal joints, all in the right side of the body. Adolescents were instructed to follow pre-test recommendations that included: 1) fasting for at least four hours; 2) light clothing, barefoot 3) without the use of earrings, rings or other metals; 4) abstaining from intense physical activity the previous day and 5) abstention from high-caffeine beverages in the previous 12 hours(14).

Independent variables Body fat (BF) percentage was calculated using the equation: %BF = 0.735 (triceps skinfold + calf skinfold) + 1(27). . To calculate fat mass (kg), the following equation was used: body mass * (%BF/100). From fat mass values, it was possible to calculate the lean mass by subtracting body mass and fat mass. Handgrip strength was measured using Saehan® hydraulic dynamometer (Model SH5001, Saehan Corporation, Masan, Korea). Handgrip strength presents high correlation (r = 0.89) with total muscle strength(33).. Evaluation procedures followed protocol described by the Canadian Society for Exercise Physiology(7).. During evaluation, adolescents were instructed to stand with arms extended to the side of the body and perform a maximal isometric contraction on the equipment that was positioned between the distal phalanges and the palm of the hand(7).. The test

8 was performed on both hands alternately, twice, and the best strength result in kilograms (kg) of each hand was recorded and summed to obtain the full strength. Abdominal resistance was obtained through the modified abdominal test proposed by the Fitnessgram® battery. The aim of this test is to complete as many sit-ups as possible up to a maximum of 75. In each sit-up, the participant complied with the distance of 11.5 cm from the initial point to the end on the mat, with both hands. In addition, the adolescent followed the cadence of a beep (beep) emitted by a metronome. Incomplete repetitions were not considered. The test was discontinued when the participant performed an incorrect repeat for the second time or reached maximum of 75 sit-ups. The 20-meter shuttle run test, proposed by Fitnessgram®, was used to obtain the maximum number of laps. It is a continuous and maximum aerobic test, with displacements and a rhythmic running form by sound signals (indicated by a recording), in a "shuttle run" distance of 20 meters(15). The test has high correlation with maximum VO 2 and was validated for adolescents(16). The test starts at 8.5 km/h and has progressive speed increment (0.5 km/h every minute). Participants moved around the bounded area and touched the line at the beep, reversing the direction of the run to the other end. The last course and the complete stage completed by adolescents were recorded.

Covariates Age (complete years) was obtained through a questionnaire, individually answered by adolescents. Sexual maturation was self-reported, based on the analysis of images of the pubertal stage of breasts and genitals(28) for girls and boys, respectively, according to Tanner's procedures (1962). The level of physical activity was measured by a list of 24 activities, validated for Brazilian adolescents (intraclass correlation coefficient = 0.88)(12) and with reproducibility by the Kappa index = 0.45 (89.3% agreement). In this list, adolescents recorded the weekly frequency and daily

9 duration of physical activities practiced in the previous week. The volume (minutes) of moderate to vigorous physical activity performed in the previous week was estimated by multiplying the frequency and duration of each activity in the list and the sum of all activities (Farias Junior et al., 2015). Screen time was measured by means of a questionnaire(14) validated (intraclass correlation coefficient = 0.72) for adolescents and with reproducibility by the Kappa index = 0.56. Screen time was obtained from a combination of four questions related to the daily time that adolescents watched TV and used the computer and / or video game (VG) during weekdays and at the weekend. These questions presented the following response alternatives: "I do not watch TV", "less than 1 hour a day", "1 hour per day", "2 hours per day", "3 hours per day", "4 hours per day" and "5 or more hours per day"(14) The combination of the screen time during weekdays and at the weekend was performed for TV and computer/VG (example: (TV week * 5) + (TV weekend * 2)/7)) and total screen time was obtained from the sum of the combinations of time on TV and computer/VG.

Characterization variables The body mass was measured with a digital scale of Filizola® (São Paulo, Brazil) brand with capacity of up to 150 kg and resolution of 100 grams. The measure was obtained from standardized procedures with the adolescents being barefoot and wearing light clothing. The evaluated ones were oriented to climb in the platform carefully, positioning in the center of the same one and distributing the weight equally on both feet. Only one measurement was performed at each evaluation. A portable, Alturaexata® (Belo Horizonte, Minas Gerais, Brazil) stadiometer with 0.1centimeter resolution was used to measure height. To perform the measurement the adolescents remained in the orthostatic position, barefoot and united, and head oriented in the Frankfort plane. The evaluator positioned his thumbs in the direction of the evaluator's ears and instructed him to

10 make and maintain a deep inhalation while holding his head in the Frankfort plane, exerting a slight upward pressure. The annotator lowered the cursor at an angle of 90 ° to the measurement scale, touching the highest point of the head and reading the measurement was done at the end of the inspiration. The body mass index was calculated from the measures of body mass and height, in the equation: (body mass (kg)/height (m)2).

Statistical analysis For the descriptive analysis of data, median, interquartile range, mean and standard deviation were calculated. Kurtosis and asymmetry were used to verify the normality of data (interval between -2 and +2) and analysis of histograms to identify normality in data distribution. Since morphological changes are related to sexual dimorphism(31), all analyses were performed stratified by sex. The composite physical fitness z-score was created based on the z-score of each physical fitness component (fat mass, lean mass, handgrip strength, and aerobic fitness [back-andforth]) adjusted for age. Thus, the composite physical fitness z-score was calculated by means of the following equation: (lean mass score-z + handgrip strength z-score + aerobic fitness z-score) - (fat mass z-score). Pearson's correlation coefficient was used to test the linear correlation between phase angle and physical fitness components (fat mass and lean mass, handgrip strength, abdominal resistance, back-and-forth test) and the composite physical fitness z-score. Simple and multiple linear regression analyses were used to test the association between outcome and exposure, adjusting for confounding factors: age and sexual maturation, level of physical activity and screen time. Regression coefficients (β), 95% confidence interval, determination coefficient for each model analyzed (R²) and effect size (Cohen's f²) were estimated. Diagnostic measures of models were analyzed as the akaike information criterion (AIC), Bayesian information criterion (BIC) and

11 variance inflation factor (VIF). For all analyses, STATA® software (StataCorp LLC, Texas, USA), version 14.0 was used, establishing p ≤ 0.05.

RESULTS A total of 1,011 adolescents were invited to participate in the study, and 353 adolescents met the eligibility criteria. The mean age of the sample was 12.5 (± 1.2) years and 55.0% of adolescents were female. Linear correlation analyses showed that the lean mass (r = 0.41, p <0.01) and handgrip strength (r = 0.41, p <0.01) (r = 0.20, p = 0.01) presented direct correlation with phase angle in male adolescents. However, only lean mass (r = 0.16, p = 0.03) was directly correlated to phase angle in females. The other variables investigated did not present statistical significance. Figure 1 summarizes correlations and 95% confidence intervals. For male adolescents, lean mass (r = 0.38, p <0.01), handgrip strength (r = 0.41, p <0.01), and the back-and-forth test (r = 0.17, p = 0.03) presented direct correlation with phase angle. In females, only lean mass z-score (r = 0.11, p = 0.03) was directly correlated to phase angle. In addition, composite physical fitness z-score was directly correlated to phase angle in male adolescents (r = 0.34, p <0.001), but not in female adolescents (r = 0.06, p = 0.06). Figure 2 summarizes correlations and 95% confidence intervals. Lean mass was directly associated with phase angle (R² = 0.16, p <0.01) in male adolescents. The increase in lean mass of 0.02 kg was associated with an increase of 0.1 degree in phase angle with small effect size (Cohen's f² = 0.19). Handgrip strength also showed association with phase angle for male adolescents (R² = 0.15, p <0.01). Thus, the increase in force of 0.03 kilograms was associated with an increase of 0.1 degree in phase angle, with small effect size (Cohen's f² = 0.18). For males, the back-and-forth test was directly associated with phase angle (R² = 0.06, p = 0.05), where the increase of 0.01 in the number of laps was associated with an increase of 0.1 degree in phase angle, with small effect size (Cohen's f² = 0.06). Analyses also showed that

12 there was no significant association between phase angle and fat mass and number of sit-ups (Table 2). For female adolescents, analyses showed direct association between lean mass and phase angle (R² = 0.05, p = 0.05), and each increase in lean mass of 0.02 kilogram was associated with an increase of 0.1 degree in phase angle. The isolated fat mass z-score was not associated with phase angle in adolescents of both sexes, even after adjustment for covariates. The lean mass (R² = 0.15, p <0.01) and handgrip strength z-scores (R² = 0.15, p <0.01) were directly associated with phase angle in male adolescents, even after adjusting for age, maturational level, habitual physical activity and screen time. Increments of 0.03 standard deviations in lean mass z-score and 0.20 standard deviations in handgrip force z-score were associated with an increase of 0.1 degree in phase angle with small effect size (lean mass: Cohen's f² = 0.16; handgrip strength: Cohen's f² = 0.18). In addition, the back-and-forth test z-score was directly associated with phase angle, but only in the crude model (R² = 0.02, p = 0.02) (Table 3). For females, only the lean mass z-score was directly associated with phase angle (R² = 0.05, p = 0.04), after adjusting for covariates. Thus, the increase of 0.02 standard deviations in lean mass z-score was associated with an increase of 0.1 degree in phase angle, with small effect size (Cohen's f² = 0.15) (Table 3). The composite physical fitness z-score was directly associated with phase angle for male adolescents (R² = 0.14, p <0.01), in which an increase of 0.09 standard deviations in the composite physical fitness z-score was associated with an increase of 0.1 degree in phase angle, with small effect size (Cohen's f² = 0.14), after adjusting for covariates. Analyses also showed that the composite physical fitness z-score was directly associated with phase angle for female adolescents, after adjusting for covariates (R² = 0.03, p = 0.05). The increment of 0.08 standard deviations in the composite physical fitness z-score was associated with an increase of 0.1 degree in phase angle with small effect size (Cohen's f² = 0.03) (Table 3).

13 DISCUSSION The main finding of this study was that isolated and grouped physical fitness indicators were directly associated with phase angle in adolescents of both sexes. These results indicate that the phase angle values can vary according to physical fitness, which indicates the use of phase angle as a marker that presents variability depending on the level of physical fitness of adolescents. This demonstrates the importance of phase angle as a useful tool to be used in physical assessments and screening of recommendations for physical activity, physical exercise, and health-related physical fitness. Physical fitness is considered one of the most important global health markers, as well as a predictor of all-cause morbidity and mortality in adults(8), because it comprises different physical functions and body structures (skeletal, cardiorespiratory and metabolic)(23). Thus, when overall physical fitness is assessed, the individual’s general health status can be identified(23), which was expressed in this study from the composite z-score, already demonstrated in other studies, although there is no consensus on the isolated indicator to be used. Previous studies have identified associations between phase angle and isolated physical fitness indicators, such as direct association with lean mass and handgrip strength(22, 18) and inverse associations with body fat (5). Although no study that have tested associations between isolated and grouped physical fitness indicators with phase angle in children and adolescents was found, the results found in the present study demonstrate the importance of maintaining good levels of physical fitness in all indicators, since there is direct association with health and cell integrity, evaluated by the phase angle. Different studies in literature have reported that healthy lifestyles and behaviors are established during childhood and adolescence, and adequate levels of physical fitness at this stage of life tend to be carried into adulthood(8). In addition, changes in puberty that impact physical fitness(23) may also influence phase angle values during adolescence(6). Therefore, it was decided to calculate the individual and composite physical fitness z-score adjusted for age. The presence and

14 magnitude of associations between phase angle and gender-specific physical fitness was evident in the present study, which occurred predominantly in males. Muscle mass, in turn, is present in greater amount in males(13), which could explain in part the association of greater magnitude in male adolescents. In the present study, lean mass was directly associated with phase angle in adolescents of both sexes. This association is expected, since lean mass is largely constituted of body water(30), which is an excellent conductor of electricity, and therefore offers low resistance to the passage of electric current (14). Consequently, low resistance values directly contribute to the increase of phase angle(22), which explains the direct association observed in the present study. Research performed with adolescents demonstrated direct association between phase angle and fat-free mass measured by X-ray absorptiometry (DXA)(19). Despite the high reproducibility of DXA, the high costs and the need for adequate physical space impair its use in field studies, such as those carried out in schools, hospitals and clubs. On the other hand, BIA is a low-cost and easy-to-perform technique that provides quick evaluation(14). Handgrip strength was directly associated with phase angle in male adolescents. Similar results were found in adolescents and adults(25,

19)

, in which higher muscle strength values were

directly associated with higher phase angle values. Phase angle is inversely proportional to resistance, which is dependent on intra and extracellular water levels. Muscle strength is directly related to muscle mass(2), which has high body water concentrations, especially intracellular water, which explains in part the association between phase angle and strength. Aerobic fitness was directly associated with phase angle in male adolescents of the present study. Phase angle is directly associated with the amount of body cell(10), considered the most metabolically active lean mass component, and higher body cell mass concentrations can provide greater energy and physical performance in the test (10). However, no previous studies that

15 investigated the relationship between phase angle and aerobic fitness were found, which limits the comparison of data. The composite physical fitness z-score was directly associated with phase angle in adolescents of both sexes in the present study. These results reinforce the direct contribution of physical fitness, defined by different indicators, in the phase angle values of adolescents. In this way, phase angle, obtained in a simple and fast way, can be a tool to be used by health professionals to complement the assessment of adolescents' health status, especially because it is a screening instrument of physical fitness indicators of adolescents. However, further studies are needed to better investigate the direction of associations, as it is not fully understood in literature whether physical fitness impacts the phase angle or whether the phase angle impacts physical fitness. This study presents strengths such as the sample size and the representativeness of adolescents. Another strong point is the use of isolated and grouped physical fitness. However, the study presents limitations such as the sample heterogeneity due to age variability. This study has observational cross-sectional design, which does not allow determining causality. In addition, the use of questionnaires to investigate physical activity and screen time may be influenced by memory bias. It could be concluded that isolated and grouped physical fitness indicators were directly associated with phase angle, even adjusted for age, maturational level, screen time and habitual physical activity, suggesting a link between cell integrity and physical fitness in young people of both sexes.

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Figure 1. Pearson's linear correlation between phase angle and physical fitness indicators, stratified by the sex of adolescents.

Figure 2. Pearson's linear correlation between phase angle and z-score isolated and composite physical fitness, stratified by the sex of adolescents.

21

Table 1. Characteristics of adolescents stratified by sex, Florianópolis, Santa Catarina, Brazil. Male (n = 159)

Female (n = 194)

Median

IIQ (p25; p75)

Mean (±sd)

Median

IIQ (p25; p75)

Mean (±dp)

p-value

Reatance (Ω /m)

50.0

45.0; 55.0

51.0 ±8.1

54.0

47.0; 60.0

54.7 ±12.7

<0.001

Resistance (Ω /m)

606.0

546.0; 654.0

605.3 ±84.4

650.0

600.0; 701.2

655.8 ±75.8

<0.001

Phase angle (degree)

5.0

4.0; 5.0

4.8 ±0.6

4.9

4.0; 5.0

4.8 ±1.0

0.064

Body mass (kg)

47.9

40.7; 57.2

50.0 ±12.7

48.4

41.9; 53.3

49.2 ±11.6

0.581

Height (cm)

156.0

148.9; 155.6

157.1 ±11.1

155.6

149.7; 160.3

154.9 ±7.8

0.037

Body mass index (kg.m-2)

19.0

17.3; 21.9

20.0 ±3.6

19.7

17.8; 22.3

20.3 ±3.8

0.424

Fat mass (kg)

2.4

1.0; 4.6

3.4 ±3.4

4.8

3.3; 6.8

6.8 ±4.2

<0.001

Lean mass (kg)

45.1

38.9; 53,5

46.1 ±10.7

43.8

337.2; 49.2

43.5 ±8.3

<0.001

Handgrip strenght (kg)

22.0

18.5; 29.0

24.6 ±8.4

22.0

18.0; 25.2

22.0 ±5.4

<0.001

Modified abdominal (repetition)

23.0

15.0; 45.0

31.5 ±22.7

16.0

9.0; 23.0

17.8 ±13.3

<0.001

Shuttle run (turns)

26.0

16.0; 40.0

29.8 ±16.4

16.0

12.0; 26.5

18.2 ±9.4

<0.001

441.0

225.0; 1111.5

840.8 ±965.9

300.0

156.2; 623.7

554.3 ±836.4

0.003

36.7

26.4; 47.0

35.7 ± 15.0

31.72

20.8; 45.0

32.8 ±16.3

0.088

Physical activity (minutes.dia-1) -1

Screen time (hours.week )

Q: interquartile range; sd: standard deviation; p25: 25th percentile; p75: 75th percentile; values in bold: p <0.05.

22

Table 2. Linear regression analysis between the phase angle and the physical fitness indicators in adolescents from Florianópolis, Santa Catarina, Brazil. Male (n = 159) β (CI95%)

R²

p

odel brute

-0.04 (-0.01; 0.07)

0.05

0.15

odel adjusted

-0.05 (-0.01; 0.07)

0.09

0.17

odel brute

0.02 (0.01; 0.03)

0.17

<0.01

odel adjusted

0.02 (0.01; 0.04)

0.16

<0.01

odel brute

0.03 (0.02; 0.04)

0.16

<0.01

odel adjusted

0.03 (0.01; 0.04)

0.15

<0.01

odel brute

-0.01 (-0.01; 0.01)

0.01

0.19

odel adjusted

-0.01 (-0.01; 0.01)

0.07

0.06

odel brute

0.01 (0.01; 0.02)

0.03

0.01

odel adjusted

0.01 (-0.01; 0.01)

0.06

0.05

Female (n = 194) VIF

AIC*; BIC

Cohen’s f²

β (CI95%)

R²

p

0.05

0.01 (-0.01; 0.05)

0.01

0.27

0.10

0.01 (-0.02; 0.05)

0.02

0.49

0.20

0.02 (0.01; 0.03)

0.02

0.02

0.19

0.02 (0.01; 0.04)

0.05

0.05

0.19

0.02 (-0.01; 0.05)

0.01

0.07

0.18

0.02 (-0.01; 0.06)

0.04

0.08

0.23

-0.01 (-0.01; 0.01)

0.01

0.36

0.07

-0.01 (-0.01; 0.01)

0.02

0.70

0.03

0.01 (-0.01; 0.01)

0.01

0.77

0.06

0.01 (-0.01; 0.02)

0.02

0.52

VIF

AIC*; BIC

Cohen’s f²

at mass (Kg)

1.03

316.64; -455.88

0.01 1.09

547.00; -374.73

0.02

Lean mass(kg)

1.28

295.69; -425.09

0.02 1.15

543. 47; -378.26

0.05

andgrip strenght (kg)

1.31

293.45; 311.35

0.07 1.17

544.42; 563.62

0.09

odified (repetition

1.08

305.98; 323.88

0.01 1.07

539.75; 558.84

0.02

huttle run (turns)

1.15

305.01; 322.91

0.01 1.06

542.72; 561. 85

0.02

23

: confidence interval; VIF: multicollinearity diagnosis; AIC *: Akaike criterion corrected; BIC: Bayesian criterion; Cohen's f²: effect size for multiple linear regression; %: percentage; kg:

lograms; rep: repetitions; Raw model: phase angle; Model adjusted: phase angle adjusted for age, sexual maturation, physical activity level and screen time.

able 3. Simple and multiple linear regression between phase angle and z-scores of the isolated and grouped indicators of physical fitness, stratified by sex in

dolescents. Male (n = 159) β (CI95%)

R²

p

VIF

AIC*; BIC

Female (n = 194) Cohen’s f²

β (CI95%)

R²

0.05

0.02 (-0.01; 0.05)

0.01

0.27

0.10

0.01 (-0.02; 0.05)

0.02

0.49

0.19

0.02 (0.01; 0.03)

0.02

0.02

0.18

0.02 (0.01; 0.04)

0.05

0.04

0.16

0.09 (-0.08; 0.27)

0.01

0.27

0.18

0.17 (-0.02; 0.36)

0.04

0.08

p

VIF

AIC*; BIC

Cohen’s f²

Z-score fat mass (sd)

Model brute

-0.04 (0.02; 0.07)

0.05

0.06

Model adjusted

-0.04 (0.01; 0.07)

0.09

0.07

Model brute

0.02 (0.01; 0.03)

0.16

<0.01

Model adjusted

0.03 (0.01; 0.04)

0.15

<0.01

Model brute

0.23 (0.144; 0.32)

0.14

<0.01

Model adjusted

0.20 (0.10; 0.30)

0.15

<0.01

1.07

306.52; -415.08

0.01 1.09

547.00; -374.73

0.02

Z-score lean mass (sd)

1.10

297.82; -423.78

0.02 1.11

543.39; -378.33

0.05

Z-score handgrip strenght (sd)

Z-score modified abdominal (sd)

1.11

293.45; -416.25

0.01 1.11

544.43; -377.30

0.09

24

Model brute

-0.06 (-0.15; 0.02)

0.01

0.16

Model adjusted

-0.09 (-0.19; 0.02)

0.07

0.06

Model brute

0.10 (0.01; 0.20)

0.02

0.03

Model adjusted

0.09 (-0.01; 0.20)

0.07

0.06

Model brute

0.10 (0.06; 0.14)

0.13

<0.01

Model adjusted

0.09 (0.04; 0.13)

0.14

<0.01

1.08

305.98; -403.72

0.01

-0.10 (-0.33; 0.11)

0.01

0.33

0.08

-0.04 (-0.28; 0.19)

0.02

0.71

0.02

0.01 (-0.22; 0.22)

0.01

0.99

0.06

0.07 (-0.16; 0.31)

0.02

0.52

0.15

0.04 (-0.05; 0.13)

0.01

0.35

0.16

0.08 (-0.07; 0.18)

0.03

0.05

0.01 1.07

539.76; 363.50

0.02

Z-score shuttle run (sd)

1.12

305.00; -404.69

0.01 1.09

542.72; -366.69

0.02

Composite z-score (dp)

1.14

290.48; -407.35

0.01 1.14

539.37; 558.49

0.03

: confidence interval; VIF: multicollinearity diagnosis; AIC *: Akaike criterion corrected; BIC: Bayesian criterion; Cohen's f²: effect size for multiple linear regression; %: percentage; kg:

lograms; rep: repetitions; Raw model: phase angle; Model adjusted: phase angle adjusted for age, sexual maturation, physical activity level and screen time.