Estudo das respostas metabólicas, antropométricas e cardiopulmonares em crianças obesas submetidas.. por Ana Carolina Ramos e Côrte de Araujo - Versão HTML

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106 (10)

0.020*

-0.896

PAD (mmHg)

TC (n=15)

66 (10)

61 (6)

0.140

-0.532

TI (n=15)

66 (8)

62 (6)

0.330

-0.462

27

4.6 Análise de responsividade

A análise de responsividade indica que as variáveis cardiopulmonares

são as que melhores respondem ao treinamento. Entre as cinco primeiras

variáveis observadas no rank, três estão relacionadas à aptidão aeróbia. As

demais estão relacionadas à resistência à insulina (Índice HOMA e

insulinemia). Em geral, ambos os grupos apresentaram comportamento

similar aos parâmetros analisados no rank final. (Tabela 5).

Tabela 5 – Resultado da análise de responsividade com rank final

p (rank)

ES (rank)

SRM (rank)

Delta (rank)

Total

rank

TC

TI

TC

TI

TC

TI

TC

TI

TC

TI

Tempo de

0,0001 (1)

0,0002 (2)

1,1 (2)

1,3 (1)

1,5 (1)

1,1 (1)

18,5 (4)

19,2 (4)

1

1

exercício

VO2 pico

0,004 (5)

0,020 (7)

0,9 (3)

0,9 (4)

0,9 (4)

0,8 (4)

23,1 (3)

26,3 (3)

4

5

absolute

VO2 pico

0,001 (2)

0,004 (4)

0,9 (3)

1,0 (3)

1,2 (3)

0,7 (5)

17,8 (5)

13,3 (7)

2

6

relative

Velocidade

0,002 (3)

0,001 (5)

1,3 (1)

1,1 (2)

0,9 (4)

1,0 (2)

15,0 (6)

16,2 (5)

3

3

pico

HOMA

0,006 (6)

0,002 (3)

-0,7 (4)

-0,8 (5)

-0,9 (4)

-0,9 (3) -28,4 (1)

-31,3 (1)

4

2

Insulinemia

0,009 (7)

0,01 (6)

-0,6 (5)

-0,7 (6)

-0,8 (5)

-1,0 (2) -26,4 (2)

-28,3 (2)

5

4

Glicemia

0,140 (9)

0,55 (12)

-0,4 (7)

-0,5 (7)

-0,3 (8)

-0,5 (6) -2,7 (12)

-5,4 (11)

10

12

Leptinemia

0,210 (11)

0,74 (14)

-0,4 (7)

-0,3 (8)

-0,2 (9)

-0,5 (6) -7,4 (8)

-14,6 (6)

9

10

IMC

0,003 (4)

0,0001 (1)

-0,2 (8)

-0,5 (7)

-1,3 (2)

-0,8 (4) -5,0 (9)

-2,9 (14)

6

7

Circunferência

0,080 (8)

0,29 (10)

-0,6 (5)

-0,3 (8)

-0,4 (7)

-0,8 (4) -3,6 (10)

-4,0 (13)

7

11

abdominal

Peso

0,600 (14)

0,03 (8)

-0,1 (9)

-0,2 (9)

-0,7 (6)

-0,3 (8) -2,5 (13)

1,2 (15)

12

13

PAS

0,400 (13)

0,02 (7)

0,0 (10)

-0,9 (4)

-0,8 (5)

0,0 (9)

-6,6 (9)

-5,8 (10)

11

8

PAD

0,140 (9)

0,33 (11)

-0,5 (6)

-0,5 (7)

-0,2 (9)

-0,3 (8) -3,0 (11)

-6,6 (9)

9

11

Fc de

0,150 (10)

0,73 (13)

-0,7 (4)

-0,3 (8)

-0,4 (7)

-0,4 (7) -2,4 (14)

-4,9 (12)

9

13

recuperação

Reserva

0,240 (12)

0,12 (9)

0,5 (6)

0,5 (7)

0,7 (6)

0,4 (7)

10,0 (7)

6,8 (8)

8

9

cronotrópica

28

4.7 Avaliação clínica

Resultados da avaliação médica mostraram que não houve nenhuma

evidência clínica causada por exaustão ou sobrecarga excessiva, dor, lesão

osteoarticular ou muscular, ou qualquer outro evento adverso, antes, durante

ou após o treinamento.

29

5 DISCUSSÃO

O principal foco do estudo foi comparar os efeitos do TC versus TI nos

parâmetros relacionados à saúde da criança obesa. Demonstrou-se, pela

primeira vez, que ambos os tipos de exercício foram igualmente eficazes na

melhora de parâmetros metabólicos, IMC e capacidade aeróbia para essa

população.

Associado ao controle alimentar, o exercício tem sido considerado o

principal pilar no tratamento da obesidade infantil7,8,9. Entretanto, o tipo ideal

de treinamento capaz de garantir os melhores benefícios à saúde dessa

população permanece desconhecido. Nesse contexto, o TI tem sido,

recentemente, sugerido como uma alternativa ao TC para melhorar os

parâmetros metabólicos e cardiopulmonares em variadas populações,

incluindo jovens saudáveis32 e idosos com insuficiência cardíaca23. Na

população pediátrica saudável, o TI tem-se mostrado capaz de melhorar o

VO

18,26,30,42

2pico

, a velocidade máxima atingida no teste cardiopulmonar18, o

pulso de oxigênio pico e submáximo42, a capacidade pulmonar em repouso e

a resposta ventilatória ao exercício31. A partir desses dados da literatura, o

presente estudo traz como novidade: 1) a população estudada: crianças

obesas; e 2) a avaliação de outros parâmetros relacionados à saúde

(resistência insulínica e medidas de composição corporal) e à capacidade

física. Os resultados encontrados confirmam a eficácia do TI (bem como a

do TC) na melhora da capacidade aeróbia (VO2pico, tempo de exercício) na

população pediátrica, estendendo esse conhecimento a crianças obesas.

30

Interessantemente, a frequência cardíaca de recuperação, que é maior

na população obesa infantil43, foi reduzida tanto após o TI quanto o TC,

fortalecendo a hipótese da importância do exercício físico na melhora da

aptidão física e da função autonômica, independente da modalidade de

treino.

Além disso, os dois modelos de exercício foram igualmente eficientes e

substancialmente efetivos na melhora da insulina sérica e do índice HOMA,

marcadores de sensibilidade à insulina. Entretanto, os demais parâmetros

bioquímicos permaneceram inalterados. É Importante ressaltar que os

sujeitos apresentaram dados basais dentro do limite da normalidade, o que

pode explicar a ausência de alteração desses dados.

Com exceção da PAS e do peso corporal, que reduziram somente com

o TI (comparação intragrupo), ambos os tipos de treinamento foram

igualmente eficientes na melhora dos parâmetros relacionados à saúde.

Esses dados foram confirmados com a análise de responsividade baseada

no teste de “rank”, que revelou uma similaridade de respostas em ambos os

grupos, sendo aquelas relacionadas à capacidade aeróbia e à sensibilidade

à insulina mais responsivas em respostas a ambos os treinamentos. Sendo

assim, os dados permitem concluir que ambos os modelos de treinamento

podem ser usados como uma estratégia eficiente e segura na melhora de

saúde em crianças obesas.

Entretanto, é importante salientar que o exercício intermitente é uma

atividade mais “natural” à criança que o exercício contínuo e prolongado25.

Além disso, a sessão de TI foi cerca de 70% mais curta do que a sessão de

31

TC. Portanto, por ser um modelo de treinamento que demanda menos tempo

para ser realizado, e por melhor atender o padrão de atividade física

preferido pelas crianças, o TI pode ser considerado vantajoso em relação ao

TC. Estudos futuros são necessários para verificar se o TI confere mais

benefícios do que o TC no que tange à aderência ao exercício físico.

Esse estudo apresenta algumas limitações. Primeiramente, não há um

grupo controle. Crianças foram recrutadas de um hospital em que recebiam

tratamento multidisciplinar para a obesidade. Tendo em vista que o exercício

é tratamento de primeira linha para obesidade infantil, seria eticamente

inaceitável impedir que um grupo de pacientes praticasse o treinamento

físico. Além disso, é importante salientar o que a curta duração do estudo

torna improvável a possibilidade de que mudanças maturacionais tenham

influenciado os resultados. De fato, nenhum dos participantes apresentou

modificação no estágio maturacional após a intervenção.

O curto período de seguimento pode ser considerado outra limitação,

impedindo conclusões definitivas sobre a segurança e eficácia das

intervenções.

Finalmente, na tentativa de identificar claramente os efeitos do

treinamento, não houve nenhuma intervenção alimentar ou tratamento

farmacológico. Novos estudos devem investigar os possíveis efeitos

sinérgicos entre os tipos de treinamento e intervenções farmacológicas e

não farmacológicas.

O exercício físico é uma das estratégias mais eficientes no tratamento

da obesidade infantil. Entretanto, pouco se sabe sobre os diferentes efeitos

32

proporcionados por diferentes protocolos de treinamento. Nesse contexto, o

presente estudo traz evidências de que o TI pode ser tão eficiente quanto o

“tradicional” TC na melhora de parâmetros relacionados à saúde em

crianças obesas. Do ponto de vista prático, o TI pode ser incorporado em

programas terapêuticos que objetivem o tratamento da obesidade infantil, já

que este tipo de exercício consome pouco tempo e é mais prazeroso para a

população infantil. Sob uma perspectiva científica, entretanto, devemos

ressaltar que algumas questões ainda devem ser esclarecidas, tais como: 1)

O TI é eficaz em longo prazo? 2) O TI é tão seguro para crianças obesas

quanto o TC? 3) As crianças obesas realmente preferem o TI ao TC?

Estudos que contemplem maiores e mais diversificadas coortes são

necessários para responder a estas questões e ampliar nosso conhecimento

acerca desse emergente tipo de treinamento.

33

6 CONCLUSÃO

Tanto o TI quanto o TC foram, em geral, igualmente eficientes na

melhora de importantes parâmetros relacionados à saúde (ex.: aptidão

aeróbia, sensibilidade à insulina, IMC) em crianças obesas. Em virtude da

equivalência de resposta do TI e do TC, o primeiro emerge como uma nova

e eficiente estratégia de treinamento, que demanda pouco tempo de

execução e apresenta elementos motivacionais, capaz de promover

benefícios à saúde em crianças obesas.

34

7 ANEXOS

Anexo A – Termo de Consentimento Livre e Esclarecido

35

TERMO DE CONSENTIMENTO LIVRE E ESCLARECIDO

HOSPITAL DAS CLÍNICAS DA FACULDADE DE MEDICINA DA

UNIVERSIDADE DE SÃO PAULO-HCFMUSP

DADOS DE IDENTIFICAÇÃO DO SUJEITO DA PESQUISA OU RESPONSÁVEL

LEGAL

1. NOME: ___________________________________________________

DOCUMENTO DE IDENTIDADE Nº : ______________________________

SEXO :

M □

F □

DATA NASCIMENTO: ___/___/___

ENDEREÇO__________________________________________________

Nº______________ BAIRRO: ____________________________________

CIDADE: ______________________ CEP:___________________________

TELEFONE: DDD (____)_________________________________________

2. RESPONSÁVEL LEGAL: ______________________________________

NATUREZA (grau de parentesco, tutor, curador etc.): __________________.

DOCUMENTO DE IDENTIDADE:_________________________

SEXO:

M □

F □

DATA NASCIMENTO: ___/___/___

ENDEREÇO__________________________________________________

Nº______________ BAIRRO: ____________________________________

36

CIDADE: ______________________ CEP:___________________________

TELEFONE: DDD (____)_________________________________________

DADOS SOBRE A PESQUISA

1. TÍTULO DO PROTOCOLO DE PESQUISA:

Estudo

das

respostas

metabólicas,

antropométricas

e

cardiopulmonares em crianças obesas submetidas ao treinamento

intermitente comparadas ao treinamento contínuo.

2 PESQUISADOR :_____________________________________________

CARGO/FUNÇÃO:______________________________________________

INSCRIÇÃO CONSELHO REGIONAL Nº ____________________________

UNIDADE DO HCFMUSP: _____________________________________

3. AVALIAÇÃO DO RISCO DA PESQUISA:

SEM RISCO

RISCO MÍNIMO X

RISCO MÉDIO

RISCO BAIXO

RISCO MAIOR

4.DURAÇÃO DA PESQUISA : 3 meses

1 – Desenho do estudo e objetivo(s):

Em crianças e adolescentes a prática regular de exercícios físicos é

comprovadamente benéfica, melhorando a saúde física e mental destes

indivíduos. Muitos trabalhos já demonstraram benefícios do exercício físico

em paciente com obesidade. Há poucos estudos sobre o tipo de treinamento

37

ideal para a criança que garanta resultados melhores para a saúde. É

provável que um programa de exercícios adequado e individualizado

melhore sua condição física e psicológica.

Essas informações estão sendo fornecidas para a participação

voluntária do seu filho(a) neste estudo, que visa melhorar a capacidade

física (respiratória, força muscular e alongamento) através do exercício físico

programado e supervisionado por médicos, fisioterapeutas e educadores

físicos.

2 – Descrição dos procedimentos que serão realizados, com seus propósitos

e identificação dos que forem experimentais e não rotineiros:

Levantaremos a ficha médica do seu filho para saber sobre o grau de

obesidade, as alterações que essa doença já promoveu na saúde de seu

filho como: pressão alta, colesterol aumentado, glicemia aumentada.

Teremos o cuidado de saber o estágio do tratamento, os remédios que ele

toma, e outras informações que possam ser úteis. Seu filho responderá

questionários e será examinado em consulta e em laboratório. Seu filho será

ainda questionado sobre possíveis dores nas articulações durante o

exercício e sobre a quantidade de exercícios que faz durante o dia. Ele

passará por uma avaliação que incluirá testes de alongamento e de esforço

físico - que é um teste para medir a força do músculo. Além disso fará um

teste de esforço na esteira (ergoespirometria) que avalia o coração e a

capacidade respiratória.

Seu filho(a) praticará exercícios físicos cuidadosamente planejados,

duas vezes por semana, durante 12 semanas, com supervisão e

acompanhamento feito pelo médico, pelo fisioterapeuta e pelo professor de

educação física.

3 – Relação dos procedimentos rotineiros e como são realizados:

Será realizada coleta de sangue por punção periférica da veia do

antebraço no início e após 3 meses de treinamento. Será, ainda, realizado

38

um teste de esforço na esteira (ergoespiromentria) antes do treinamento,

após 6 semanas do início do treino e após o término do treinamento (12

semanas).

4 – Descrição dos desconfortos e riscos esperados nos procedimentos dos

itens 2 e 3:

De uma forma geral, seu filho não está sujeito a riscos durante a

prática dos exercícios, já que durante todo o período ele estará sendo

avaliado e monitorizado por profissionais da área da saúde. A criança,

porém, pode se queixar de dores no corpo após o treino. O exercício será

suspenso caso ocorra qualquer desconforto ou evento inesperado que possa

prejudicar seu filho.

Avaliação da capacidade respiratória - O exame para avaliar a

capacidade respiratória pode ocasionar algum cansaço na hora da

execução. Seu filho(a) também poderá sentir um pouco de dor nos músculos

até 2 dias depois do teste.

Programa de Exercícios - Durante o programa de exercícios ele poderá

sentir cansaço na primeira semana, o que provavelmente não acontecerá

nas outras semanas de exercício.

Exame de sangue – a coleta de sangue poderá causar um leve desconforto

no local da picada, que deve desaparecer em um dia.

Teste de esforço na esteira (ergoespirometria) – o objetivo do teste é

avaliar o comportamento do coração, da pressão e do pulmão durante o

exercício e ainda dar informações para prescrever o treino do seu filho. Por

ser um teste de esforço na esteira, a criança poderá sentir cansaço durante

o teste e, ocasionalmente, dores musculares no dia seguinte ao teste.

5 – Benefícios para o participante

Seu filho será avaliado e iremos desenvolver um programa de

exercícios adequado à sua condição clínica e física. Participando dele com

regularidade ele poderá melhorar sua condição física, o que irá permitir que

39

possa fazer suas atividades diárias com mais disposição, adquirindo mais

força muscular e capacidade respiratória. Além disso, com a realização

correta do programa de exercício e o controle alimentar segundo a orientaçã

da nutricionista, seu filho irá perder peso.

6 – Relação de procedimentos alternativos que possam ser vantajosos,

pelos quais o paciente pode optar;

Seu filho passará por um programa de exercícios cuidadosamente

desenvolvido para a sua condição física e clínica que poderá levar a melhora

da sua capacidade de executar as tarefas do dia-a-dia e diminuir a sensação

de cansaço. Será acompanhado por médicos, fisioterapeutas e professores

de educação física durante todo o período. Qualquer sintoma ou mudança

na sua condição física poderá ser avaliado e tratado de forma adequada e

individualizada.

7 – Garantia de acesso:

Em qualquer etapa do estudo, você terá acesso aos profissionais

responsáveis pela pesquisa para esclarecimento de eventuais dúvidas. O

principal investigador é a Dra Ana Carolina Corte de Araujo que pode ser

encontrada no LACRE (Laboratório de Avaliação e Condicionamento em

Reumatologia) do Hospital das Clínicas da FMUSP, no 4º andar do Prédio

dos Ambulatórios, Av. Dr Enéas de Carvalho Aguiar, 255. Telefone 3069-

8022. Se você tiver alguma consideração ou dúvida sobre a ética da

pesquisa, entre em contato com o Comitê de Ética em Pesquisa (CEP) –

Rua Ovídio Pires de Campos, 225 – 5º andar – tel: 3069-6442 ramais 16, 17,

18 ou 20, FAX: 3069-6442 ramal 26 – E-mail: cappesq@hcnet.usp.br

8 – É garantida a liberdade da retirada de consentimento a qualquer

momento e deixar de participar do estudo, sem qualquer prejuízo à

continuidade de seu tratamento na Instituição;

40

09 – Direito de confidencialidade – As informações obtidas serão analisadas

em conjunto com outros pacientes, não sendo divulgado a identificação de

nenhum paciente;

10 – Direito de ser mantido atualizado sobre os resultados parciais das

pesquisas, quando em estudos abertos, ou de resultados que sejam do

conhecimento dos pesquisadores;

11 – Despesas e compensações: não há despesas pessoais para o

participante em qualquer fase do estudo, incluindo exames e consultas.

Também não há compensação financeira relacionada à sua participação.

12 - Compromisso do pesquisador de utilizar os dados e o material coletado

somente para esta pesquisa.

Acredito ter sido suficientemente informado a respeito das

informações que li ou que foram lidas para mim, descrevendo o estudo

Estudo

das

respostas

metabólicas,

antropométricas

e

cardiopulmonares em crianças obesas submetidas ao treinamento

intermitente comparadas ao treinamento contínuo.

Eu discuti com a Dra Ana Carolina Corte de Araujo sobre a minha

decisão em participar nesse estudo. Ficaram claros para mim quais são os

propósitos do estudo, os procedimentos a serem realizados, seus

desconfortos e riscos, as garantias de confidencialidade e de

esclarecimentos permanentes. Ficou claro também que minha participação é

isenta de despesas e que tenho garantia do acesso a tratamento hospitalar

quando necessário. Concordo voluntariamente em participar deste estudo e

poderei retirar o meu consentimento a qualquer momento, antes ou durante

41

o mesmo, sem penalidades ou prejuízo ou perda de qualquer benefício que

eu possa ter adquirido, ou no meu atendimento neste Serviço.

_________________________________________________________

Assinatura do paciente/representante legal

Data:__________/___________/__________

Assinatura da testemunha

Data:__________/___________/__________

para casos de pacientes menores de 18 anos, analfabetos, semi-analfabetos

ou portadores de deficiência auditiva ou visual.

...........................................................................................................................

(Somente para o responsável do projeto)

Declaro que obtive de forma apropriada e voluntária o Consentimento Livre e

Esclarecido deste paciente ou representante legal para a participação neste

estudo.

_________________________________________________________

Assinatura do responsável pelo estudo

Data:__________/___________/__________

42

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APÊNDICE 1

Artigo “Similar Health Benefits of Endurance and High-

Intensity Interval Training in Obese Children”, publicado

na PLoS ONE, em agosto de 2012 – www.plosone.org

Similar Health Benefits of Endurance and High-

Intensity Interval Training in Obese Children

Ana Carolina Corte de Araujo1, Hamilton Roschel1,2,4,Andreia Rossi

Picanço1, Danilo Marcelo Leite do Prado1,Sandra Mara Ferreira

Vil ares3, Ana Lúcia de Sá Pinto1,Bruno Gualano1,2*

1 University of Sao Paulo, School of Medicine – Division of Rheumatology,

Sao Paulo, Sao Paulo, Brazil, 2 University of Sao Paulo, School of Physical

Education and Sport – Laboratory of Nutrition and Metabolism Applied to

Exercise, Sao Paulo, Sao Paulo, Brazil, 3 University of Sao Paulo, School of

Medicine – Division of Endocrinology, Sao Paulo, Sao Paulo, Brazil, 4

University of Sao Paulo, School of Physical Education and Sport –

Laboratory of Neuromuscular Adaptations to Strength Training, Sao Paulo,

Sao Paulo, Brazil

Abstract

Purpose. To compare two modalities of exercise training (i.e., Endurance

Training [ET] and High-Intensity Interval Training [HIT]) on health-related

parameters in obese children aged between 8 and 12 years. Methods. Thirty

obese children were randomly al ocated into either the ET or HIT group. The

ET group performed a 30 to 60-minute continuous exercise at 80% of the

peak heart rate (HR). The HIT group training performed 3 to 6 sets of 60-s

sprint at 100% of the peak velocity interspersed by a 3-min active recovery

period at 50% of the exercise velocity. HIT sessions last ~70% less than ET

sessions. At baseline and after 12 weeks of intervention, aerobic fitness,

body composition and metabolic parameters were assessed. Results. Both

the absolute (ET: 26.0%; HIT: 19.0%) and the relative VO2 peak (ET: 13.1%;

HIT: 14.6%) were significantly increased in both groups after the intervention.

Additional y, the total time of exercise (ET: 19.5%; HIT: 16.4%) and the peak

velocity during the maximal graded cardiorespiratory test (ET: 16.9%; HIT:

13.4%) were significantly improved across interventions. Insulinemia (ET:

29.4%; HIT: 30.5%) and HOMA-index (ET: 42.8%; HIT: 37.0%) were

significantly lower for both groups at POST when compared to PRE. Body

mass was significantly reduced in the HIT (2.6%), but not in the ET group

(1.2%). A significant reduction in BMI was observed for both groups after the

intervention (ET: 3.0%; HIT: 5.0%). The responsiveness analysis revealed a

very similar pattern of the most responsive variables among groups.

Conclusion. HIT and ET were equal y effective in improving important health

related parameters in obese youth.

Citation: Corte de Araujo AC, Roschel H, Picanço AR, do Prado DML,

Vil ares SMF, et al. (2012) Similar Health Benefits of Endurance and High-

Intensity Interval Training in Obese Children. PLoS ONE 7(8): e42747.

doi:10.1371/journal.pone.0042747

Editor: Reury F. P. Bacurau, University of Sao Paulo, Brazil

Received: May 7, 2012; Accepted: July 12, 2012; Published: August 6,

2012

Copyright: © 2012 Corte de Araujo et al. This is an open-access article

distributed under the terms of the Creative Commons Attribution License,

which permits unrestricted use, distribution, and reproduction in any medium,

provided the original author and source are credited.

Funding: The authors have no support or funding to report.

Competing interests: The authors have declared that no competing

interests exist.

* E-mail: gualano@usp.br

INTRODUCTION

The incidence of juvenile obesity has dramatical y increased worldwide in the

last fifty years, mainly as a result of a physical y inactive lifestyle and

inappropriate diet habits [1], [2]. Not surprisingly, the most successful

interventions aimed at preventing or treating obese children have primarily

focused on physical fitness promotion, along with behavioral and nutritional

counseling [1], [3], [4].

In spite of that, it is stil unclear which type of exercise is capable of eliciting

the greatest health benefits to obese children. Traditional y, the low-to-

moderate-intensity endurance training (ET) has been the most common type

of exercise recommended to improve body composition, physical capacity

and overal health-related parameters (e.g., blood pressure, insulin

resistance, lipid profile) in healthy and obese people [3], [4]. However,

recently, a growing body of literature has also supported the efficacy of high-

intensity interval training (HIT) in promoting health-related effects in healthy

children[5], [6] and

adults [7], [8],

and

individuals

with

metabolic

syndrome [9] and congestive heart failure[10].

The HIT consists of high-intensity exercise bouts interspersed by an interval

period between the sets. The claimed advantage of HIT relies in the fact that

this type of training is less-time consuming than ET, while producing

comparable

beneficial

adaptations.

For

instance,

Tjønna

et

al. [9] demonstrated that a 16-week, three times a week HIT (i.e., four 4-

minute bouts at 90% of maximal heart rate with a 3-minute active recovery)

and ET (i.e., 47 minutes at 70% of maximal heart rate) programs were

equal y effective in lowering mean arterial blood pressure and reducing body

mass and fat in metabolic syndrome patients. Nonetheless, HIT was superior

to ET in enhancing endothelial function, skeletal muscle biogenesis, and

excitation-contraction coupling and in reducing blood glucose and lipogenesis

in adipose tissue. Using a similar approach, Wisløff et al. [10] found similar

results in heart failure patients. Peak oxygen consumption (VO2peak) and

endothelial function improved more with HIT than moderate ET and was

associated with reverse left ventricular remodeling. Moreover, quality of life

was equal y improved in both groups. In healthy young subjects, serial

studies by Gibala's laboratory have showed that HIT (i.e., six repeats of a 30-

s al -out Wingate Test with 4.5 min recovery between repeats) and ET (i.e.,

40–60 min of continuous cycling at a workload that elicited ~65% of VO2peak)

induce similar metabolic, cardiovascular and skeletal muscle molecular

adaptations in healthy humans [7], [11]. In a recent review, Gibala and

Mcgee [8] stated that in young healthy persons of average fitness, HIT is a

time-efficient strategy to stimulate a number of skeletal muscle adaptations

that are comparable to traditional ET. The authors, however, stressed the

fact that “fundamental questions remain regarding the minimum volume of

exercise necessary to improve physiological wel -being in various populations

and the effectiveness of alternative (less extreme) interval-training

strategies”.

Prolonged physical activities (i.e., >30 min) are contrary to a child's pattern of

spontaneous exercise, which mainly comprises short-term intermittent

efforts [12], [13]. It is wel -known that children usual y present higher

perceived exertion in response to prolonged exercise [14]. This, along with

psychological and cultural factors (e.g., shorter attention span, the need for

recreational simuli, or motivation), may explain a child's preference for

activities of shorter duration. Therefore, HIT emerges as a promising time-

efficient and more motivational strategy capable of promoting health

adaptions in children. In fact, a few studies have corroborated the potential of

HIT training in inducing cardiovascular adaptations in healthy pediatric

populations [15], but none of them have compared the efficacy of

HIT versus ET in physical y-inactive obese youth.

Given that exercise has been recognized as a major cornerstone of juvenile

obesity management, efforts focused on determining the ideal type of training

for treating this condition are of great relevance. Thus, the aim of this study

was to compare two modalities of exercise training (i.e., HIT and ET) on

health-related parameters in obese children.

MATERIALS AND METHODS

Study sample and experimental design

One hundred outpatients were recruited from the Obesity Clinics

(Endocrinology Department, School of Medicine, University of Sao Paulo,

Brazil). Sixty-one did not meet inclusion criteria. Thirty-nine consecutive

outpatient children were selected. The inclusion criteria were as fol ows: (1)

age between 8 and 12 years; (2) BMI = 95th percentile, according to the First

National Health and Nutrition Examination Survey; (3) no pharmacological

treatment; (4) no evidence of metabolic, hormonal, orthopedic, and

cardiovascular disease at the time of the study's commencement; and (5) no

participation in any regular exercise training program (except physical

education classes, two days a week) at least 6 months before the

commencement of the study and throughout the protocol. Children were

randomly al ocated into 2 groups: endurance training (ET) and sprint interval

training (HIT). Subjects' demographic characteristics are presented in Table

1.

index-70_1.png

Table 1. Main patients' characteristics.

At baseline (PRE) and after 12 weeks (POST) of exercise training, aerobic

fitness, body composition and metabolic parameters were assessed. Food

intake was assessed at PRE and POST, but no dietetic intervention was

implemented. Throughout the study, the children and their parents received

generic counseling by a professional nutritionist regarding the benefits of

adopting healthy eating patterns. Children were submitted to medical

examination on a weekly basis and possible adverse events were recorded.

The protocol was approved by the local Ethics Committee (General Hospital,

School of Medicine, University of Sao Paulo) and written consent was

obtained from al patients' parents at the beginning of the study.

Pubertal evaluation

Pubertal developmental stage was determined according to the methods

described by Marshal and Tanner [16], [17].

Anthropometric measurements

Body mass was measured by an electronic body mass scale with children

dressed in a light T-shirt and shorts. Height was measured by a stadiometer.

Waist circumference was measured at the level of the umbilicus, using a non-

stretchable tape.

Bioelectrical impedance

Body composition was analyzed by bioelectrical impedance method using a

standardized body composition analyzer (BiaQuantum RJL Systems, Inc, MI,

EUA). Percentage of body fat was estimated using a validated equation

adjusted for gender, age, weight, and height, fol owing previously described

procedures [18]. Children were instructed to refrain from drinking and eating

for 4 hours before the test and exercising for at least 12 hours before the test.

Arterial Pressure

Sitting systolic and diastolic blood pressure (SBP and DBP, respectively)

were recorded fol owing standard procedures and using a mercury column

sphygmomanometer, after a 5-min period of absolute rest and with the

patient seated.

Metabolic parameters

Blood samples were col ected through a catheter inserted into the antecubital

vein after a 12-hour fasting period. Serum glucose, insulin, glycated

hemoglobin (Hb1aC), leptin, total cholesterol and sub-fractions (i.e., LDL-,

HDL- and VLDL-cholesterol) and triglyceride (TG) were measured in the

clinical laboratory of the General Hospital (School of Medicine, University of

Sao Paulo, Brazil) using standardized methods. The Homeostasis Model

Assessment for Insulin Resistance (HOMA-IR) was calculated using the

fol owing equation: (insulin resistance = insulin (µU/ml)×glucose

(mmol/L)/22.5).

Maximal graded cardiorespiratory test

A modified Balke treadmil (Centurion, model 200, Micromed, Brazil) test was

performed. Oxygen consumption (VO2) and carbon dioxide output (CO2)

were obtained through breath-by-breath sampling and expressed as a 30-

second average using an indirect calorimetry system (Cortex - model

Metalyzer III B, Leipzig, Germany). Heart rate (HR) was continuously

recorded at rest, during exercise and at recovery, using a 12-lead

electrocardiogram (Ergo PC Elite, InC. Micromed, Brazil). The recovery

period was set at four minutes using the initial workload (1.9 mph). Peak

oxygen consumption (VO2peak) and ventilatory threshold (VT) and respiratory

compensation point (RCP) were determined according to previously

described criteria [19]. Time-to-exhaustion was recorded for each test.

Additional y, HR recovery (∆HRR) was defined as the difference between HR

at peak exercise and at both first (∆HRR1) and second (∆HRR2) minutes

after exercise.

Food intake assessment

Food intake was assessed at PRE and POST by three 24-h dietary recal s

undertaken on separate days (2 weekdays and 1 weekend day). To help

subjects estimate portion sizes, a visual aid photo album of real foods

(Portion Photos of Popular Foods, 1997 - The American Dietetic Association,

Chicago, IL, USA) and real-size three-dimensional fake food samples (TBW,

São Paulo, SP, Brazil) were used. The 24-h dietary recal consists of the

listing of al foods and beverages consumed during the 24 h prior to the

recal . Energy and macronutrient intake were analyzed by the software

Dietpro 5.1 Professional.

Training Protocols

The training protocols consisted of walking/running exercise on a treadmil

(Centurion, model 200, Micromed, Brazil) performed twice a week on

alternate days for 12 weeks.

The ET group performed a 30-minute continuous endurance exercise at 80%

of the peak HR. Training progression in the ET group was applied by

increasing the exercise duration by 10 minutes every three weeks, until a

total of 60 minutes during the last three weeks of intervention (i.e., from

weeks 10 to 12). HR was continuously monitored during exercise to ensure

that the subjects trained at the target intensity. The ET energy cost estimated

by indirect calorimetry ranged from 268.1±61.4 to 536.2±122.8 Kcal,

considering 30 and 60 minutes of exercise, respectively.

The HIT protocol consisted of repeated 60-second efforts (covered distance

per bout: 118±14.5 m) at 100% of the peak velocity (determined by the

maximal graded cardiorespiratory test), interspersed by a 3-min active

recovery period at 50% of the peak velocity. Training progression was

applied by adding one bout of exercise every three weeks. The number of

bouts ranged from 3 (within the first 3 weeks) to 6 (within weeks 10–12). The

HIT energy cost (recovery periods included) ranged from 84.0±1 5.3 to

169.7±30.6 Kcal, considering 3 and 6 bouts of exercise, respectively.

After 6 weeks of training, a new maximal graded cardiorespiratory test was

conducted for training intensity adjustments.

Statistical Analysis

After the normality and homogeneity of the variance were confirmed, the

dependent variables were compared using a mixed model analysis with

repeated measures (SAS 8.2, SAS Institute Inc., Cary, NC, USA) assuming

group and time as the fixed factors and subjects as the random factor. A post

hoc test adjusted by Tukey was used for multicomparison purposes.

Significance level was previously set at p<0.05. Data are presented as mean

± standard deviation. Additional y, we performed a responsiveness analysis.

To that end, commonly used indices of responsiveness (standardized

response mean (SRM), Cohen's effect size (ES), percent change from

baseline, and p values from the mixed model analysis) were used. The SRM

was calculated by dividing the mean change in scores by the standard

deviation of the change whereas the ES was calculated by dividing the mean

change by the standard deviation of the baseline value (PRE) for each

parameter. Final y, we calculated an overal rank of responsiveness. The

rank was computed based on the sum score for al 4 responsiveness

statistics. Only the parameters that showed statistical significance were

included in the rank analysis.

RESULTS

The number of patients recruited to the study is shown in Figure 1. Al of the

100 volunteers who responded to the initial request were screened and 39

met the inclusion criteria. These patients were randomly assigned to either

the ET (n = 20) or HIT (n = 19) groups. Nine patients withdrew from the study

for personal reasons (five from the ET group and four from the HIT group).

Therefore, 30 patients were analyzed (ET = 15; HIT = 15). The adherence to

the training program was similar between groups (85.5 and 86.9%, for the ET

and HIT, respectively). Food intake remained unchanged after the

intervention (Total energy intake – ET PRE: 1925 POST: 1893 kcal; HIT

PRE: 2380 POST: 2365 kcal; Carbohydrate intake – ET PRE: 50.1 POST:

49.9%; HIT PRE: 48.3 POST: 43.0%; Protein intake – ET PRE: 19.0 POST:

19.6%; HIT PRE: 16.4 POST: 15.5%; Lipid intake – ET PRE: 30.7 POST:

index-76_1.jpg

30.0%; HIT PRE: 35.2 POST: 41.5%; p>0.05 for within- and between-group

comparisons).

Figure 1. Fluxogram of patients.

Both the absolute (ET: 26.0%; HIT: 19.0%) and the relative VO2 peak (ET:

13.1%; HIT: 14.6%) were significantly increased in both groups after the

intervention. Additional y, the total time of exercise (ET: 19.5%; HIT: 16.4%)

and the peak velocity during the maximal graded cardiorespiratory test (ET:

16.9%; HIT: 13.4%) were significantly improved across interventions (Figure

2).

index-77_1.jpg

Figure 2. Effects of ET and HIT on cardiorespiratory and exercise

parameters in response to a maximal graded exercise test.

Panel A: VO2 peak (L/min); Panel B: VO2(ml/kg/min); Panel C: Total time of

exercise (min); Panel D: Peak velocity (mph); ET = endurance training group;

HIT = high-intensity interval training; PRE = baseline; POST = after twelve

weeks of training. * indicates p<0.05 (within-group comparison).

∆HRR1 and ∆HRR2, which are markers of aerobic fitness and autonomic

function, were significantly increased in the HIT group (38.5 and 21%,

index-78_1.jpg

respectively), whereas only deltaHRR2 increased in the ET group (38.8%)

(Figure 3).

Figure 3. Effects of ET and HIT on absolute changes in heart-rate

recovery.

Panel A: absolute changes at the first (∆ HRR1 min) minute of recovery after

a maximal graded exercise test at baseline (PRE) and after twelve weeks of

training (POST). Panel B: absolute changes at the second (∆ HRR2 min)

minute. ET = endurance training group; HIT = high-intensity interval training;

* indicates p<0.05 (within-group comparison); # indicates main time effect

(p<0.05).

Insulinemia (ET: 29.4%; HIT: 30.5%) and HOMA-index (ET: 42.8%; HIT:

37.0%) were significantly lower for both groups at POST when compared to

PRE. The other biochemical parameters remained unchanged in both groups

(Table 2).

index-79_1.png

Table 2. Effects of ET and HIT on anthropometric measurements and

arterial blood pressure in obese children.

Body composition parameters are shown in Table 3. Body mass was

significantly reduced in the HIT (2.6%), but not in the ET group (1.2%).

Despite of the slight reduction in body mass observed in the HIT group, no

between-group differences were found at the POST test. A significant

reduction in BMI was observed for both groups after the intervention (ET:

3.0%; HIT: 5.0%).

index-80_1.png

Table 3. Effects of ET and HIT on metabolic parameters in obese

children.

The responsiveness statistics indicate the cardiorespiratory variables as the

most responsive parameters fol owing the intervention. Amongst the five top-

ranked variables, three were related to the aerobic fitness. The remaining

variables were related to the glucose metabolism (i.e., HOMA-index and

insulinemia). In general, both groups presented rather similar parameters in

the total ranking (Table 4).

index-81_1.png

Table 4. Ranking of the studied parameters.

Based upon the medical examination, no clinical evidence of excessive

exhaustion, pain, osteoarticular injury, muscle soreness, or any other

adverse event was noticed.

DISCUSSION

The main focus of this study was to compare the effects of ET versus HIT on

health-related parameters in obese youth. We demonstrated for the first time

that the both types of training were equal y effective in improving metabolic

parameters, BMI, and aerobic fitness in this sample.

Along with dietetic counseling, exercise has been considered the major

cornerstone of juvenile obesity management [1], [3], [4]. However, the

optimal type of training capable of eliciting the most important health benefits

to obese children remains debatable. In this context, HIT has been recently

suggested as an alternative method to ET for metabolic and cardiovascular

status improvement for broad populations, from young health adults [11] to

old heart failure patients[10]. In health pediatric populations, HIT has been

shown to improve VO2peak [5], [15], [20], [21], maximal velocity in the

incremental test [5], high-intensity intermittent performance[15], peak and

submaximal oxygen pulse[20], and resting pulmonary function and ventilatory

response to exercise [22]. In light of these previous findings, the novelty of

the current study was two-fold: 1) the investigation of physical y-inactive

obese children; and 2) the evaluation of other health-related parameters

(e.g., insulin resistance and body composition measures) in addition to

performance-related variables in a pediatric sample.

The present results confirm the efficacy of HIT (to the same extent as ET) in

improving aerobic fitness (e.g., VO2peak, time-to-exhaustion) in pediatric

populations, extending this notion to obese youth. Interestingly, HR recovery,

which is significantly delayed in juvenile obesity [23], was also improved

fol owing both HIT and ET, further supporting the therapeutic role of exercise

in improving physical fitness and autonomic function, irrespective of the

training modality.

Furthermore, both exercise modes were equal y and substantial y effective in

improving insulinemia and HOMA-index, which are surrogate markers of

insulin sensitivity. However, the other biochemical parameters remained

stable. In this respect, it is worth noting that the individuals presented

metabolic parameters within a desirable range, which might explain the lack

of changes in potential y modifiable factors, such as lipid profile.

With exception of SBP and body mass which were attenuated solely in the

HIT group (within-group comparisons), both HIT and ET were equal y

effective in promoting health-related effects. This was further confirmed by a

comprehensive responsiveness analysis based on the rank tests, which

revealed a very similar pattern among groups of the most responsive

variables, with those related to aerobic fitness and insulin sensitivity being

situated in the top-five rank. Col ectively, the present data al ow concluding

that both HIT and ET may be used as an efficient and safe strategy to

improve health in obese youth. However, one must be aware that children

may be natural y prone to short bouts of intensive exercise rather than

prolonged continuous exercise [12]. Moreover, it is important to emphasize

that HIT sessions was substantial y less time-consuming (~70%) than ET

sessions. Thus, the fact that HIT is a time-efficient strategy that meets the

child's preference of physical fitness may be considered an advantage of this

exercise type over ET. Long-term studies should verify whether HIT training

does confer more beneficial results in terms of adherence and consequently

health outcomes in comparison with ET.

This study presents some limitations. First, a control group was not included.

Children were recruited from a medical hospital where they receive

multidisciplinary treatment for obesity. Given that exercise is the first line

treatment for juvenile obesity, it would be ethical y unacceptable to have our

outpatients refrain from exercise. Notwithstanding this recognized limitation, it

is important to stress the short-term characteristic of this study, mitigating the

impact of the maturation on the study's outcomes and, hence, the lack of the

non-trained group. In support of this, none of the individuals had the sexual

maturation status changed after the intervention. Second, the short-term

fol ow-up itself is another limitation, precluding definitive conclusions

regarding the safety and efficacy of the interventions. Final y, to al ow clearly

distinguishing the effect of the training, exercise training was not

accompanied by any dietetic prescription or psychological therapy. Further

studies should investigate the possible synergistic effect of these types of

training in addition to non-pharmacological interventions.

Exercise training is one of the most efficient strategies in the treatment of

juvenile obesity. However, little is known on the differential effects yielded by

alternative training protocols. In this respect, the current study provided

evidence that HIT may be as effective as traditional ET in improving general

health parameters in obese children. From a practical standpoint, HIT may be

incorporated into therapeutic programs aimed to treat juvenile obesity, since

this mode of exercise is less-time consuming and probably more pleasant to

children population. From a scientific perspective, however, one should be

aware that there are questions remaining on this topic stil to be elucidated,

such as: “Does the efficacy of HIT hold true on a long-term basis?” , “Is HIT as

safe as ET in obese children?” , “Do obese children real y prefer HIT over

ET?” , “Do energy expenditure-matched HIT and ET programs produce

comparable health benefits?”. Further studies with large and diversified

cohort of obese children wil be necessary to address these questions and

advance our knowledge on this emerging type of training.

In conclusion, both HIT and ET were equal y effective in improving important

health parameters (e.g., aerobic fitness, insulin sensitivity, BMI) in obese

children. In light of the equivalence of HIT and ET, the former emerges as a

novel time-efficient and potential y motivational strategy capable of promoting

health adaptations in juvenile obesity.

ACKNOWLEDGMENTS

We are grateful to Fundação de Amparo à Pesquisa do Estado de São Paulo

(FAPESP), Conselho Nacional de Pesquisa e Desenvolvimento (CNPq), and

Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior (CAPES)

for supporting our studies.

AUTHOR CONTRIBUTIONS

Conceived and designed the experiments: BG HR ALdSP ACCdA.

Performed the experiments: ACCdA ARP DMLdP. Analyzed the data:

ACCdA ARP ALdSP BG HR. Contributed reagents/materials/analysis tools:

ACCdA SMFV ALdSP. Wrote the paper: BG HR ACCdA. Statistical

expertise: HR BG.

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