Effect of Intensity and Duration of Exercise on Gut Microbiota in Humans: A Systematic Review

Ci a ion: Bonomini-Gnu zmann, R.; Plaza-Díaz, J.; Jo que a-Aguile a, C.; Rod íguez-Rod íguez, A.; Rod íguez-Rod íguez, F. E ec o In ensi y and Du a ion o Exe cise on Gu Mic obio a in Humans: A Sys ema ic Re iew. In . J. En i on. Res. Public Heal h 2022,19, 9518. h ps://doi.o g/10.3390/ije ph 19159518 Academic Edi o : Paul B. Tchounwou Recei ed: 15 June 2022 Accep ed: 25 July 2022 Published: 3 Augus 2022 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2022 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). In e na ional Jou nal o En i onmen al Resea ch and Public Heal h Re iew E ec o In ensi y and Du a ion o Exe cise on Gu Mic obio a in Humans: A Sys ema ic Re iew Romina Bonomini-Gnu zmann 1, Julio Plaza-Díaz 2,3,4,* , Ca los Jo que a-Aguile a 1,*, And és Rod íguez-Rod íguez 5and Fe nando Rod íguez-Rod íguez 6 1Escuela de Nu ición y Die é ica, Facul ad de Ciencias, Uni e sidad Mayo , San iago 8580745, Chile; [email p o ec ed] 2Child en’s Hospi al o Eas e n On a io Resea ch Ins i u e, O awa, ON K1H 8L1, Canada 3Depa men o Biochemis y and Molecula Biology II, School o Pha macy, Uni e si y o G anada, 18071 G anada, Spain 4Ins i u o de In es igación Biosani a ia IBS.GRANADA, Complejo Hospi ala io Uni e si a io de G anada, 18014 G anada, Spain 5Gas ic Cance Resea ch G oup—Labo a o y o Oncology, UC Cen e o In es iga ional Oncology (CITO), Pon i icia Uni e sidad Ca ólica de Chile, San iago 8331150, Chile; [email p o ec ed] 6IRyS G oup, Physical Educa ion School, Pon i icia Uni e sidad Ca ólica de Valpa aíso, Valpa aíso 2374631, Chile; e nando. od iguez@puc .cl *Co espondence: j plaza@ug .es (J.P.-D.); ca los.jo que a@mayo .cl (C.J.-A.); Tel.: +34-958241599 (J.P.-D.); +569-95791706 (C.J.-A.) Abs ac : (1) Backg ound: The gu mic obio a migh play a pa in a ec ing a hle ic pe o mance and is o conside able impo ance o a hle es. The aim o his s udy was o sea ch he ecen knowledge o he p o agonis played by high-in ensi y and high-du a ion ae obic exe cise on gu mic obio a composi ion in a hle es and how hese e ec s could p o ide disad an ages in spo s pe o mance. (2) Me hods: This sys ema ic e iew ollows he PRISMA guidelines. An exhaus i e bibliog aphic sea ch in Web o Science, PubMed, and Scopus was conduc ed conside ing he a icles published in he las 5 yea s. The selec ed a icles we e ca ego ized acco ding o he ype o s udy. The isk o bias was assessed using he Joanna B iggs Ins i u e’s C i ical App aisal Tool o Sys ema ic Re iews. (3) Resul s: Thi een s udies had nega i e e ec s o ae obic exe cise on in es inal mic obio a such as an upsu ge in I-FABP, in es inal dis ess, and changes in he gu mic obio a, such as an inc ease in P e o ella, in es inal pe meabili y and zonulin. In con as , se en s udies obse ed posi i e e ec s o endu ance exe cise, including an inc ease in he le el o bac e ia such as inc eased mic obial di e si y and inc eased in es inal me aboli es. (4) Conclusions: A la ge pa o he s udies ound epo ed ad e se e ec s on he in es inal mic obio a when pe o ming endu ance exe cises. In s udies ca ied ou on a hle es, mo e nega i e e ec s on he mic obio a we e ound han in hose ca ied ou on non-a hle ic subjec s. Keywo ds: ae obic exe cise; adul s; eli e a hle es; la ge in es ine; gu mic obio a 1. In oduc ion The in es inal o gu mic obio a is “ he se o mic obes ha colonize ou diges i e ac ha in e ac wi h each o he and wi h he hos ” [1–3]. Cu en ly, mo e han one housand di e en mic obial species ha e been ound ha can eside in he human gas oin es inal ac [ 4 ]. App oxima ely one hund ed six y species a e ound in he la ge in es ine [ 3 ], de eloping a biomass o mo e han 1.5 kg [ 5 ]. The mic obio a con ain bac e ia, as well as ungi, i uses, and p o is s [ 1 ]. The mos abundan and di e se amilies o bac e ia in he adul gas oin es inal ac a e Ac inobac e ia,Bac e oide es,Fi micu es, and P o eobac e ia, and less di e se a e Ve ucomic obia,Len isphae ae,Sine gis e es,Planc omyce es,Tene icu es, and Deinococcus-The mus [2,3]. In . J. En i on. Res. Public Heal h 2022,19, 9518. h ps://doi.o g/10.3390/ije ph19159518 h ps://www.mdpi.com/jou nal/ije ph In . J. En i on. Res. Public Heal h 2022,19, 9518 2 o 17 The composi ion o he gu mic obio a is o med h oughou ea ly childhood, induced by gene ic and en i onmen al ac o s [ 1 – 3 ]. The ma u a ion o he in es inal mic obio a in he adul ype is gone a he age o h ee yea s [ 1 , 6 ]. Fac o s such as age, li es yle, die , and gene ics can al e he gu mic obio a, c ea ing a dynamic ecosys em [ 7 ]. O he ela ed ac o s could include mode o deli e y, geog aphy, b eas eeding, weaning, and exposu e o en i onmen al bac e ia [ 1 ]. Some esea che s p oposed ha he in es inal mic obio a can ac as an endoc ine o gan [ 8 ] and can ha e an eno mous impac on human heal h, including he immune unc ion, physiology, me abolism, and nu i ion o he hos [ 9 ]. In he same line, he gu mic obio a pe o ms a se ies o p o ec i e, s uc u al, and me abolic unc ions essen ial o he heal h o he hos , including ood handling, he inges ion o complex polysaccha ides no diges ible by he hos , he mo emen o pa hogens, and he syn hesis o i amins among o he s [ 10 ]. Obse a ional s udies ha e ound ha in es inal mic obio a may con ibu e ei he o he pa hogenesis o a ious common me abolic diso de s including ype 2 diabe es, obesi y, ca dio-me abolic diseases, malnu i ion, and non-alcoholic li e disease, as well as o he me abolic heal h o he human hos [ 11 ]. Heal hy gu mic obio a shows an essen ial ole in he con igu a ion o he local and sys emic immune unc ion o in es inal bac e ia h oughou li e, a o ing he main enance o ole ance owa d an igens o he commensals and ac i a ion agains an igens o commensal pa hogens [ 12 ]. The in es inal mic obio a plays an impo an ole in he egula ion o hos ene gy me abolism, hyd a ion s a us, sys emic in lamma o y esponses, and oxida i e s ess [13]. Physical exe cise is desc ibed as he implemen a ion o some ac i i y in o de o imp o e o p ese e o e all heal h and physical i ness [ 14 , 15 ]. Cu en ly, physical exe cise is ecognized as a o midable p e en i e and ea men media ion ha is ecognized o be e icien in causing bene i s o immune and me abolic heal h [ 15 , 16 ]. Endu ance exe cise is desc ibed as ca dio ascula ac i i y, o example: cycling, unning, swimming, skiing, and owing ha is pe o med o a long ime, ou o six hou s pe day, six days pe week [ 17 ]. This in ense exe cise includes p ocesses ha in ol e physiological, a ec i e, cogni i e–beha io al, and biochemical esponses in an e o o eco e homeos asis [9]. Some p o essional a hle es expe ience immunosupp ession o gas oin es inal symp- oms, such as abdominal pain, dia hea, o leaky gu synd ome [ 8 ]. Al e a ions in he in es inal mic obio a p oduced by s enuous exe cise can also p oduce exe cise-induced gas oin es inal diso de s [ 18 ]. Some symp oms ha a e s a ed du ing he pe o mance o endu ance exe cise include bloa ing, nausea, c amps, and dia hea [ 19 ]. I has been s udied ha exe cising o exhaus ion can dis up he balance among he gu mic obio a and he immune sys em [ 12 ]. Exe cise-induced gas oin es inal damage o in lamma ion could ad e sely a ec a hle ic ou ine and, in some cases, ha e compe i ion d opou [ 20 ]. An- o he s udy men ions ha in ense exe cise c ea es inc eased gas oin es inal damage, mild endo oxemia, and in es inal pe meabili y [21]. The main inding in pos -exe cise gas oin- es inal p oblems is possible ischemia– epe usion inju y de eloping om a momen a y in e up ion o splanchnic blood low. When he in ense physical exe cise inishes, we ob- se ed igge ing eac i e oxygen species (ROS) p oduc ion, damage o he gas oin es inal mucosa, and in lamma ion [22]. Likewise, i is li le known hus a how high-in ensi y exe cise in luences he in es inal mic obio a [ 21 ]. The impo ance o knowing he mechanisms in which he in es inal mic obio a migh ha e an impo an ole in a ec ing a hle ic ou ine is o signi ican a en ion o a hle es wo king o expand hei compe i i e pe o mance and diminish ecupe a ion ime du ing aining [ 12 ]. Such in o ma ion could ha e an ad an age in he comp ehension o gu mic obio a in luences on a hle e heal h [12]. The e o e, he main aim o his sys ema ic e iew is o elucida e he knowledge o he unc ion played by high-in ensi y and high-du a ion ae obic exe cise on gu mic o- bio a composi ion in a hle es and how hese e ec s could p o ide disad an ages in hei spo s pe o mance. In . J. En i on. Res. Public Heal h 2022,19, 9518 3 o 17 2. Ma e ials and Me hods 2.1. Sea ch S a egy This sys ema ic e iew ollows he PRISMA guidelines [ 23 ]. An exhaus i e biblio- g aphic sea ch o h ee da abases (Web o Science, PubMed, and Scopus) was conduc ed conside ing he a icles published in he las 7 yea s ( om 1 Janua y 2015 o 31 Augus 2021). Table 1shows he sea ch s a egy in he Web o Science, PubMed, and Scopus da abases. This sys ema ic e iew was lis ed on he PROSPERO (In e na ional p ospec i e egis e o sys ema ic e iews) websi e on 5 May 2022, wi h he ollowing eco d CRD42022323300. A ailable om: h ps://www.c d.yo k.ac.uk/p ospe o/display_ eco d.php?ID=CRD420 22323300 (accessed on 14 June 2022). Table 1. Sea ch s a egy in da abases. Da abase Sea ch S a egy Limi s Fil e s Web o Science (ALL (Physical ac i i y AND gu mic obio a OR Physical ac i i y AND in es inal ba ie OR Physical ac i i y AND in es inal pe meabili y OR Physical exe cise AND gu mic obio a OR Physical exe cise AND in es inal ba ie OR Physical exe cise AND in es inal pe meabili y)) Ti le A icles English 238 i ems il e ed PubMed (Physical ac i i y OR physical exe cise) AND (gu mic obio a OR in es inal ba ie OR in es inal pe meabili y) Ti le A icles English Humans 104 i ems il e ed Scopus TITLE-ABS-KEY (physical AND ac i i y AND gu AND mic obio a) OR (physical AND ac i i y AND in es inal AND ba ie ) OR (physical AND ac i i y AND in es inal AND pe meabili y) OR (physical AND exe cise AND gu AND mic obio a) OR (physical AND exe cise AND in es inal AND ba ie ) OR (physical AND exe cise AND in es inal AND pe meabili y) AND (LIMIT-TO (OA, “all”)) AND (LIMIT-TO (PUBYEAR, 2022) OR LIMIT-TO (PUBYEAR, 2021) OR LIMIT-TO (PUBYEAR, 2020) OR LIMIT-TO (PUBYEAR, 2019) OR LIMIT-TO (PUBYEAR, 2018) OR LIMIT-TO (PUBYEAR, 2017) OR LIMIT-TO (PUBYEAR, 2016) OR LIMIT-TO (PUBYEAR, 2015)) AND (LIMIT-TO (DOCTYPE, “a ”)) AND (LIMIT-TO (LANGUAGE, “English”)) Ti le A icles English 5934 i ems il e ed 2.2. Selec ion and Exclusion C i e ia The selec ion c i e ia we e: (i) a icles w i en in English, (ii) da abases a o emen ioned, (iii) human s udies, (i ) o iginal a icles: clinical ials, andomized con olled ials (RCTs) quasi-expe imen al, long- e m, p ospec i e, and c oss-sec ional s udies, ( ) a icles om Janua y 2015 o Augus 2021. The exclusion c i e ia we e: (i) s udies ha include people wi h pa hologies, (ii) s udies ha include animals, (iii) s udies ha comp ise child en unde 18 yea s o age and olde adul s (+65 yea s), (i ) s udies ha in e ened wi h supplemen s o some die , ( ) case s udies, case epo s, le e s o he edi o , sys ema ic e iew and me a-analyses and na a i e e iew. No es ic ions we e placed on he body composi ion o he ained subjec . A e emo ing epea ed documen s, sui abili y was measu ed by e alua ion o he manusc ip i le and abs ac and la e e alua ion o he ull ex . 2.3. Da a Ex ac ion and Reliabili y The sea ch was ca ied ou by i e independen e iewe s (R.B.-G., F.R.-R., J.P.-D., C.J.-A. and A.R.-R.). They ead he i les and abs ac s o all e ie ed a icles. A mee ing was held o esol e disag eemen s abou eligibili y. The ollowing in o ma ion was collec ed om each included s udy: he i s au ho , yea o publica ion, ype o s udy, objec i e, he numbe o subjec s, body mass index (BMI), maximum oxygen consump ion (VO 2max ), In . J. En i on. Res. Public Heal h 2022,19, 9518 4 o 17 gende , and age when i was a ailable, ype o exe cise, how he exe cise was ca ied ou , he molecula analysis used o he de ec ion o he gu mic obio a, he main esul s ob ained, and conclusions. The selec ed a icles we e ca ego ized acco ding o he ype o s udy (low-, medium-, o high-in ensi y o long- e m exe cise in e en ions). The esul s o he s udies ha me he selec ion c i e ia o hei eco e y we e examined. 2.4. Assessmen o he Quali y and Le el o E idence The isk o bias was assessed using he Joanna B iggs Ins i u e’s C i ical App aisal Tool o Sys ema ic Re iews. In summa y, his ool includes ou speci ic checklis s depending on he s udy design (i.e., c oss-sec ional, quasi-expe imen al, coho , RCTs s udies). The answe s o each o hem had ou possible ca ego ies: “yes” (c i e ion me ) and “no” (c i e ion no me ). Speci ic ools included: eigh i ems o c oss-sec ional s udies, nine i ems o quasi-expe imen al, and hi een i ems o RCTs. Acco ding o he abo e, he s udies we e conside ed as “low quali y” e idence when ≤ 49% o he i ems we e classi ied as “yes” (c i e ion me ). Following, he a icles we e conside ed as “medium quali y” e idence be ween 50–74% o he i ems we e sco ed as “yes” and “high quali y” e idence when ≥ 75% o he i ems we e classi ied as “yes”. The answe s “no applicable” and “non- clea ” we e excluded by pe cen age [ 24 – 26 ]. The i e e iewe s assessed he s udies’ quali y sepa a ely. A consensus mee ing was o ganized o esol e possible di e ences be ween he e iewe s. 3. Resul s Figu e 1displays he chosen epo ing elemen s o sys ema ic e iews and he low cha o he sea ch s a egy. A o al o 6277 s udies we e loca ed in he h ee da abases assessed. Then, 95 s udies we e excluded o duplica es and 6136 s udies we e excluded a e eading he i le and abs ac ha we e ou side he opic o he e iew. A o al o 45 s udies we e assessed o eligibili y. A e analyzing he exclusion c i e ia, six een s udies we e included. Se en s udies had an obse a ional design (i.e., i e c oss-sec ional and wo long- e m designs), and nine s udies had an expe imen al design (eigh we e quasi-expe imen al, and one was RCT). Table 2shows he summa y o he s udies included. This e iew is ocused on da a om 513 pa icipan s, and he sample size anged om 4 o 86 subjec s. Two o he six een s udies in ol ed only women [ 18 , 27 ], six in ol ed only men [ 5 , 13 , 16 , 28 – 30 ], i e in ol ed bo h men and women [ 7 , 9 , 22 , 31 , 32 ] and h ee s udies did no epo he sex o he sub- jec s [ 19 , 33 , 34 ]. The age o he subjec s anged om 18 and 49 yea s; wo s udies did no epo he age o he subjec s [ 28 , 33 ]. The samples we e om 10 di e en coun ies: h ee s udies we e led in Poland, wo in Spain, wo in he Uni ed S a es, wo in China, wo in I eland, one in he Uni ed Kingdom, one in Aus alia, one in Belgium, one in Ge many and one om Japan. Rega ding he cha ac e is ics o he sample, ele en s udies o he six een we e con- duc ed on endu ance a hle es ( unne s, cyclis s, and ia hle es). Among hese nine s udies conside ing medium- and long-dis ance unne s [ 5 , 13 , 16 , 18 , 22 , 29 , 30 , 32 , 33 ], h ee s udies inco po a ed physically ac i e subjec s [ 27 , 31 , 34 ], one s udy on ia hle es [ 19 ], a s udy on cyclis s [ 7 ], a s udy included ma ial a s p o essionals [ 9 ], and a s udy on ugby play- e s [ 28 ]. Mos o he s udies inco po a ed in his sys ema ic e iew (81%) used ecal samples o de e mine changes in he in es inal mic obio a. O hese, mainly 75% de e mined he 16S ibosomal RNA gene ic sequence ha is commonly used o iden i ica ion, classi ica ion, and quan i a ion o mic obes wi hin complex biological mix u es such as en i onmen al samples and in es inal samples. A mino i y o ou s udies (25%) used plasma samples h ough he p o ein enzyme-linked immunoso ben assay es o de e mine ma ke s such as in es inal a y-acid binding p o ein (I-FABP) ela ed o mucosal damage, zonulin associ- a ed wi h in es inal pe meabili y, and co isol, c- eac i e p o ein, and TNF- α ela ed o a p oin lamma o y s a us. In . J. En i on. Res. Public Heal h 2022,19, 9518 5 o 17 In . J. En i on. Res. Public Heal h 2022, 19, x 5 o 18 Figu e 1. Flowcha o a icles h ough he sea ch p ocess. Table 2 shows he summa y o he s udies included. This e iew is ocused on da a om 513 pa icipan s, and he sample size anged om 4 o 86 subjec s. Two o he six een s udies in ol ed only women [18,27], six in ol ed only men [5,13,16,28–30], i e in ol ed bo h men and women [7,9,22,31,32] and h ee s udies did no epo he sex o he subjec s [19,33,34]. The age o he subjec s anged om 18 and 49 yea s; wo s udies did no epo he age o he subjec s [28,33]. The samples we e om 10 di e en coun ies: h ee s udies we e led in Poland, wo in Spain, wo in he Uni ed S a es, wo in China, wo in I eland, one in he Uni ed Kingdom, one in Aus alia, one in Belgium, one in Ge many and one om Japan. Rega ding he cha ac e is ics o he sample, ele en s udies o he six een we e con- duc ed on endu ance a hle es ( unne s, cyclis s, and ia hle es). Among hese nine s udies conside ing medium- and long-dis ance unne s [5,13,16,18,22,29,30,32,33], h ee s udies inco po a ed physically ac i e subjec s [27,31,34], one s udy on ia hle es [19], a s udy on cyclis s [7], a s udy included ma ial a s p o essionals [9], and a s udy on ugby playe s [28]. Mos o he s udies inco po a ed in his sys ema ic e iew (81%) used ecal samples o de e mine changes in he in es inal mic obio a. O hese, mainly 75% de e mined he 16S ibosomal RNA gene ic sequence ha is commonly used o iden i ica ion, classi ica- ion, and quan i a ion o mic obes wi hin complex biological mix u es such as en i on- men al samples and in es inal samples. A mino i y o ou s udies (25%) used plasma samples h ough he p o ein enzyme-linked immunoso ben assay es o de e mine ma ke s such as in es inal a y-acid binding p o ein (I-FABP) ela ed o mucosal damage, zonulin associa ed wi h in es inal pe meabili y, and co isol, c- eac i e p o ein, and TNF- α ela ed o a p oin lamma o y s a us. Figu e 1. Flowcha o a icles h ough he sea ch p ocess. The esul s e ealed ha nine s udies showed nega i e e ec s o ae obic exe cise on he in es inal mic obio a. Among hese ad e se e ec s, h ee s udies ound an inc ease in I-FABP [ 5 , 16 , 29 ], one s udy p esen ed in es inal dis ess [ 5 ], h ee s udies obse ed nega i e changes in he mic obiome [ 30 – 32 ], wo s udies ound an inc ease in P e o ella [ 7 , 33 ], h ee s udies obse ed an inc ease in in es inal pe meabili y [ 16 , 19 , 29 ], and wo s udies epo ed an inc ease in zonulin [ 19 , 29 ]. In con as , se en s udies obse ed posi i e e ec s o en- du ance exe cise, including an inc ease in he le el o bac e ia such as Rosebu ia hominis, Bi idobac e ium spp., Akke mansia muciniphila,Faecalibac e ium p ausni zii [ 18 , 27 ], Co iobac e i- aceae [22], inc eased mic obial di e si y [9,13,33] and inc eased in es inal me aboli es [28]. Addi ionally, an analysis has been pe o med o de e mine he s udy quali ies included in his e iew. Fo his, he Joanna B iggs Ins i u e’s c i e ium checklis (Table 3) was used. Di e en c i e ia we e used acco ding o he cha ac e is ics o he s udies. In his ega d, one s udy ul illed 100% o he c i e ia [ 27 ], and se en s udies ul illed ≥ 75% o he quali y c i e ia [ 7 , 9 , 13 , 27 , 28 , 31 , 33 ], classi ying hemsel es as high quali y. The es o he s udies [ 5 , 16 , 18 , 19 , 22 , 29 , 30 , 32 , 34 ] we e classi ied as medium quali y because hey ob ained a alue be ween >50% and <75% o he c i e ia (among 50–69.2%). No s udies wi h low quali y we e ound (<50% o he c i e ia). In . J. En i on. Res. Public Heal h 2022,19, 9518 6 o 17 Table 2. Cha ac e is ics as he ype o s udy, aim, sample, design, and mean esul s o he s udies. Au ho , Yea Type o S udy AIM Sample S udy Design Resul s Pugh e al. (2017) [5] Quasi-Expe imen al Cha ac e ize he HIIT e ec s on small in es inal damage ma ke s n= 11 (men unne s ained) Aged 33.1 ±10.4; VO2max 60.0 ±3.2 mL/kg/min Acu e HIIT episode ma ke s o in es inal pe meabili y and damage we e e alua ed and compa ed wi h es ing condi ions. Minimum unning pe o mance o 10 km (39 min) and a minimum o 5 wo kou sessions pe week, using se um sampling, p e-exe cise, a e each se o exe cises, and 2 h pos -baseline HIIT signi ican ly inc eased he se um lac ulose: hamnose a io and suc ose concen a ions compa ed wi h es . In con as , u ina y lac ulose: hamnose o suc ose concen a ions did no a y be ween s udy g oups. Plasma I-FABP augmen ed in he ecupe a ion pe iod om HIIT only. A e 24 h o HIIT, he esea che s ound mild symp oms o GI dis ess Liang e al. (2019) [9] C oss-sec ional Whe he he in es inal mic obio a is dis inc i e be ween highe -le el and lowe -le el a hle es n= 31 (p o essional ma ial a s a hle es). 15 women and 16 men; aged 20–24 Ma ial a s a hle es; Wushu ou ine, igo ous, as and dynamic spo s. The esea che s used 16S RNA gene sequencing o de e mine he in es inal changes Highe -le el a hle es ha e augmen ed me abolic capaci y and di e si y in he in es inal mic obio a compa ed wi h lowe -le el a hle es. Pe e sen e al. (2017) [7] C oss-sec ional De e mine he p esence o dis inc i e o ganisms in p o essional and ama eu le el compe i i e cyclis s n = 33 (p o essional and ama eu le el compe i i e cyclis s); 11 women and 22 men; aged 19–49 The s udy used me a ansc ip omic (RNA-Seq) sequencing and mWGS The inc ease in P e o ella was associa ed wi h ime epo ed exe cising du ing an a e age week. Se e al p o essional cyclis s ha e augmen ed le els o Me hanob e ibac e smi hii ansc ip s compa ed wi h ama eu cyclis s. B essa e al. (2017) [27] C oss-sec ional Compa e in es inal composi ion among wo g oups di ided by physical exe cise le els n= 40 (p emenopausal women). 19 ac i e and 21 seden a y Aged 18–40; BMI 20–25 kg/m2 The esea che s used 16S RNA gene sequencing o de e mine he in es inal changes Pe o mance o physical ac i i y was associa ed wi h he p esence o heal h-p omo ing bac e ia (R. hominis,A. muciniphila, Bi idobac e ium spp., and F. p ausni zii). Dec eased le els o di e si y we e co ela ed wi h seden a y pa ame e s In . J. En i on. Res. Public Heal h 2022,19, 9518 7 o 17 Table 2. Con . Au ho , Yea Type o S udy AIM Sample S udy Design Resul s Ka hu e al. (2017) [16] Quasi-expe imen al E alua e he e ec o unning on GI unc ion ma ke s n= 17 (ac i e unne s); 8 women and 9 men; aged 18–45 The esea che s measu ed seconda y a iables, such as zonulin, le els o se um in es inal I-FABP, and bac e ial LPS, among o he s Bo h, se um I-FABP and in es inal pe meabili y inc eased a e unning, wi hou di e ences amongs g oups. No changes we e obse ed in he bac e ial LPS in se um Keohane e al. (2019) [13]Long- e m Analyze he changes in he in es inal mic obio a o ou well- ained male a hle es o p olonged, high-in ensi y ans-oceanic owing n= 4 (men a hle es ansa lan ic owing). Aged 25–27; BMI 23–25 kg/m2; VO2Max 46–50 mL/kg/min Me agenomic whole-genome sho gun sequencing was used In ense exe cise clea ly impac s he di e si y o he in es inal mic obio a, wi h changes in speci ic bac e ia ela ed o me abolic pa hways Bycu a e al. (2021) [31] Quasi-expe imen al Impac o CRE o RTE on in es inal mic obio a n= 56 n= 28 CRE g oup (21 women; Aged 20.7; BMI 24.5 kg/m2and 7 men; aged 20; BMI 24.0 kg/m2.n= 28 RTE g oup (17 women; aged 20.4; BMI 23.2 kg/m2and 11 men; aged 22.6; BMI 24.59 kg/m2 In es inal mic obio a was measu ed using 16S RNA gene sequencing The obse ed changes we e associa ed only wi h he CRE g oup, esul ing in dis u bance o he in es inal mic obio a Mo ishima e al. (2020) [18]C oss-sec ional E ec s o highly in ensi e endu ance exe cise on he in es inal mic obio a and i s ela ionship wi h he onse o he exe cise-induced GI diso de s n= 29 (15 women Japanese endu ance unne s and 14 nona hle ic bu heal hy women). Aged 20–21; BMI 20.7–21.9 kg/m2 Fecal mic obio a was es ed using 16S RNA me agenomics, and o he a iables such as mois u e con en , o ganic acids, and pu e ac i e me aboli es concen a ions we e examined Female eli e endu ance unne s ha e mo e abundance o Faecalibac e ium, and hese changes could be associa ed wi h he succina e concen a ion in his g oup To a e al. (2019) [19] Long- e m E alua e in es inal and muscle damage in ia hle es n= 15 ( ia hle es). Aged 6–14; VO2max 58.8 ±4.5 mL/kg/min Va iables used o he analysis we e: co isol, c- eac i e p o ein, zonulin, and TNF-α Zonulin and a iables o pe meabili y we e augmen ed a e he ace In . J. En i on. Res. Public Heal h 2022,19, 9518 8 o 17 Table 2. Con . Au ho , Yea Type o S udy AIM Sample S udy Design Resul s Zhao e al. (2018) [22] Quasi-expe imen al The gu mic obio a immedia ely esponds o he en e ic changes in ama eu hal -ma a hon unne s n= 20 (4 women and 16 men ama eu hal -ma a hon unne s). Aged 31.3; BMI 22.6 kg/m2 Fecal samples we e analyzed be o e and a e he ma a hon using 16 DNA sequencing analyses Co iobac e iaceae changes we e ela ed o he exe cise ole in a oiding disease and e ining heal h ou comes. Moi inho-Sil a e al. (2021) [34] Randomized con olled ial Analyze he changes in he in es inal mic obio a on p e iously physically inac i e, heal hy adul s in compa ison o con ols ha did no pe o m egula exe cise n= 36 (11 con ols; 13 endu ance g oup; 12 s eng h g oup). Aged 22–41.3; BMI 19.7–32.5 kg/m 2 Fecal mic obio a was es ed using 16S RNA me agenomics Mucosal damage and in lamma ion we e ound a e sho - e m esis ance aining. No changes we e obse ed in in es inal mic obio a Sadowska-K epa e al. (2021) [29]Quasi-expe imen al E alua e in es inal damage in middle-aged male subjec s n= 10 (ama eu long-dis ance unne s). Aged 21–35 Va iables used o he analysis we e: TAS, TOS/TOC, hs-CRP, I-FABP, and zonulin A e he exe cise, he le els o in es inal pe meabili y bioma ke s as, hs-CRP, I-FABP, zonulin, and in lamma ion we e augmen ed Kulecka e al. (2020) [33]Quasi-expe imen al E alua e di e ences in in es inal mic obio a amongs heal hy con ols and endu ance a hle es n= 71 n= 14 ma a hon unne s; n= 11 c oss-coun y skie s; n= 46 heal hy con ol indi iduals Fecal mic obio a was es ed using 16S RNA me agenomics Excessi e aining is associa ed wi h changes in Bac e oides and P e o ella and bac e ial di e si y Tabone e al. (2021) [30] Quasi-expe imen al De e mine whe he he changes a e d i en by exe cise on he gu mic obio a (wi h 16S RNA gene) and he se um and ecal me abolome n= 40 (men endu ance c oss-coun y unne s). Aged 35.8 ±8.0; BMI 22.8 ±2.1 kg/m2; VO2max 58.8 ±3.24 mL/kg/min Fecal mic obio a was es ed using 16S RNA me agenomics The changes in gu mic obio a could be ela ed o physiological changes in ammonia, u ic acid, and lac a e In . J. En i on. Res. Public Heal h 2022,19, 9518 9 o 17 Table 2. Con . Au ho , Yea Type o S udy AIM Sample S udy Design Resul s Ba on e al. (2017) [28] C oss-Sec ional E alua e di e ences in in es inal mic obio a amongs exe cise and a mo e seden a y s a e n= 86 (40 men p o essional in e na ional ugby union playe s and 46 men con ols) Fecal mic obio a was es ed using 16S RNA me agenomics P o essional in e na ional ugby union playe s had mo e a o able e ec s in me abolic pa hways han he con ol g oup C a en e al. (2021) [32] Quasi-expe imen al E alua e di e ences in in es inal mic obio a acco ding o aining olume n= 14 (highly ained middle-dis ance unne s). n= 6 women; aged 22.0 ± 3.4; VO2max 59.0 ±3.2 mL/kg/min n= 8 men; aged 20.7 ±3.2; VO2max 70.1 ±4.3 mL/kg/min Fecal mic obio a was es ed using 16S RNA me agenomics No changes we e obse ed in in es inal mic obio a acco ding o aining olume in uppe axons. Changes in amily, genus, and species we e obse ed, hese changes did no e u n o p e-le els Abb e ia ions: AFT, a e ecal; BEF, be o e ecal; BMI, body mass index; CRE, ca dio espi a o y exe cise; DS, s anda d de ia ion; FCCS, emale c oss-coun y skie s; FDR, alse disco e y a e; FMR, emale ma a hon unne s; GI, gas oin es inal; HIIT, high-in ensi y in e al aining; hs-CRP, High-sensi i i y C- eac i e p o ein; H olT , high- olume aining; I-FABP, in es inal a y acid-binding p o ein; kg/m 2 , kilog am pe squa e me e ; LPS, lipopolysaccha ide; MCCS, male c oss-coun y skie s; MCHC, mean co puscula hemoglobin concen a ion; mL/kg/min, millili e s pe minu e pe kilog am; MMR, male ma a hon unne s; mWGS, me agenomic whole genome sho gun; No mT no mal aining; PGM, pe sonal genome machine; PWC, physical wo king capaci y; RNA, ibosomal ibonucleic acid; RTE, esis ance aining exe cise; Tape T , exponen ial educ ion in aining; TAS, o al an ioxidan s a us; TOC, o al oxidan capaci y; TOS, o al oxidan s a us; VO2max, he maximum amoun o oxygen; WHO, Wo ld Heal h O ganiza ion; WSER, Wes e n S a es Endu ance Run. 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