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BJSM Online First, published on November 16, 2016 as 10.1136/bjsports-2016-097017 10.1136/bjsports-2016-097017 Discussion
Applying the acute:chronic workload ratio in elite football: worth the effort? Martin Buchheit The The use use of the acut acute: e:chr chron onic ic work worklo load ad ratio (A/C) has received a growing interest in the past 2 years to monit mon ito or injury risk in a variety of team sports. 1 2 This This ratio ratio is generally computed over 28 days (ie, load accumulated during the current week/load accumulated weekly over the past 28 days), using both internal (session-rate of perceive exert exertion ion (Session (Session-RP -RPE)× E)×dur durati ation) on) and external external (tracking (tracking variables, variables, often Global Global Positioning ositioning System System (GPS)-rela (GPS)-related, ted, such as high-speed high-speed running running and accelera acceleration tion variables) measures of competitive and training load. While the potential bene �t of such a metric is straight forward for practitioners, there remain several limitations to (1) the assessment of relative external load and in turn, turn, injur injuryy risk risk in play player erss diff differ erin ingg in locomotor locomotor pro�les les and and (2) (2) the effe effecti ctive ve monitoring of overall load across all training and match matches es through throughout out the year year.. In turn, these limitations limitations likely likely compromise compromise the usefulness of the A/C ratio in elite football (soccer). Assessing player player ’s locomotor locomotor pro�le and and relative relative external load. 1. Speed : Consi Consider dering ing that that subtle subtle differ differ-ences in sprinting intensity such as high (85–95% of maximal maximal sprinting speed) versus very high-speed running (>95%) may have important important implicati implications ons with wit h regard regard to injury risk and preventio prevention, n, 3 the indi indivi vidu dual alis isat atio ion n of high high-sp -spee eed d runn runnin ingg zone zoness may may be impo import rtan ant. t. However, such a sprint-intensity classi �cati cation on requi equirres the the use use of pla players yers’ maximal sprinting speed as a reference, which which is very very rare rarely ly assessed assessed in elite elite playe players. rs. There Therefor fore, e, consid consideri ering ng the large large varia variation tionss in locomo locomotor tor pro pro �les between players within the same team, the use of absolute ( �xed) speed thresholds to de�ne high-speed running zones may limit the sensitivity of the A/C ratio with with resp respec ectt to high high-sp -spee eed d runn runnin ingg load3 and in turn, injury risk. Fitness: Considering that � tness testing 2. Fitness: (eg, (eg, maxim maximal al aerobi aerobicc speed) speed) is also also
Performance Department, Paris Saint-Germain Football Club, Saint-Germain-en-Laye, France Correspondence to Dr to Dr Martin Buchheit, Performance Department, Paris Saint-Germain Football Club, 4a avenue du président Kennedy, Saint-Germain-en-Laye 78100, France;
[email protected]
rare in professional football, and considering the clear impact of �tness on injury injury risk, risk,4 it is dif dif �cult cult to de�ne which A/C ratio values may be critical when monitoring players with varying and unknown unknown �tness tness levels levels (eg, (eg, A/C ratio >1.2 vs >1.5 vs >1.8). In summary, the dif �culties encountered encountered in elite elite footba football ll to de�ne player playerss’ locomotor pro�le likely likely limit limit the sensitivi sensitivity ty and and in turn turn,, the the usef useful ulne ness ss of the the A/C A/C ratio in this speci �c population.
power) or different velocity thresholds (33%). 3. Moni Monito tori ring ng sys system tem used used but but for for variou variouss reaso reasons ns the commun communica icatio tion n with the club is very limited or absent (11%). 4. No monitori monitoring ng at all all (50%). (50%). In the the best best case casess (sce (scena nari rios os 1 and and 2 abov above), e), exter external nal load load can be estim estimat ated ed throughout the break (thereby aggregating both both club club and and nati nation onal al team team trai traini ning ng// matches data), and A/C ratios can be computed on return. In the worst and most frequent cases (scenarios 3 and 4), there is a net loss of external workload monitoring ing for for club club pra practit ctitio ione ners rs for for abou aboutt 10 days days duri during ng each each brea break k ( �gu gurre 1), which which in turn turn compr compromi omises ses the prope properr use of the A/C ratio for a month, which often often coinci coincides des with with the timing timing of the next break! To avoid arti �cial spikes/drops spikes/drops ( �gu gurre 1), the the leas leastt bad bad opti option on may may consis consistt in using using playe players rs’ historica historicall club data data to predi predict ct the missi missing ng sessio session n and match loads (based on training schedules and match playing times). While predicted data may be better than no data at all, the vera veracit cityy of the predi predicte cted d data data rema remains ins uncertain, and the trustability of the associated A/C ratios, questionable.
Integrating data from different tracking systems: systems: In comp compar aris ison on to othe otherr team team sports, an important methodological challeng lengee to moni monitor tor exte extern rnal al load load in elit elitee footbal footballl is that that traini training ng and matche matchess are are often often trac tracked ked with with differ different ent syste systems ms (eg, (eg, GPS during during traini training ng and semiau semiautom tomati aticc cameras cameras for matches). matches).5 Of course, course, practipractitione tioners rs can can use use calibratio alibration n equations equations to integrate all data; 5 however, (1) these speci�c equations are not always readily avail- Lack of load monitoring during the offable able and (2) betwe betweenen-sy syste stem m agreem agreement entss season period : The inabil inability ity to monito monitorr are never perfect, especially especially for the most load during the off-season leads to unrealimpo importa rtant nt vari variab able les, s, that that is, is, high high--speed isti isticc A/C A/C rati ratio o valu values es duri during ng the the �rst 5 running running and accelera acceleration tion variables. variables. The week weekss of train training ing during during the prese preseaso ason n prec precis isio ion n of the A/C A/C rati ratio o obta obtain ined ed for for period (fully realistic ratios likely obtained those those variab variables les is there therefor foree questi questionab onable le only only when when the the chro chroni nicc load load is whol wholly ly and may may also also decre decrease ase its sensitiv sensitivity ity and established, ie, after 28 days, �gure 1). 1). An alte altern rnat ativ ivee opti option on duri during ng this this peri period od usefulness. could be to reduce the duration required Dealing with international duties: duties: In all to calcul calculat atee chroni chronicc load, load, but the most most elite elite clubs, clubs, there there may may be at least least 10 –12 appropriate duration to select remains to internat internationa ionall player playerss within within each each team; team; be de�ned (2 vs 3 vs 4 weeks). each of them travelling in-season for intersession-R n-RPE PE method method:: a soluti solution on to national duty for 8 –10 days, 4–5 times a The sessio these limita limitation tions? s? While year. year. These ‘international international breaks’ repre- these While inte intern rnal al and and sent one of the greatest challenge for club external external loads are two separa separate te compocomposport scientists scientists seeking seeking to keep keep track track of nents of load which cannot be used intertheir player playerss’ competiti competition on and trainin trainingg chan change geab ably ly, it is beli believ eved ed tha that the the load load,, sinc sincee in the the vast vast majo majori rity ty of the the sess sessio ionn-RP RPE E meth method od may may offe offerr some some cases national teams staff use monitoring advantages over measures of external load approach approaches es and system systemss that that differ differ sub- in the speci speci�c conte context xt of elite elite footba football. ll. stan stanti tial ally ly from from thos thosee used used in play player erss ’ First, the validity of session-RPE to quanclubs. clubs. The likely likely differe different nt scenarios scenarios are tify exercise intensity and in tur n, overall the following (the % in bracket shows the training load, is well established. 6 Second, proportion of players for each case in a severa severall studies studies have have shown shown good associaassociaFrench Ligue 1 club sending 18 players in tions tions betwe between en change changess in sessio session-R n-R PE PE 1 2 nine different national teams): load and injury risks in various sports. 1. Monitoring system system similar similar to that that used Finally and more importantly, RPE can be in the club (5%). collected across: 2. Monitori Monitoring ng system system in place place but using ▸ all sessio sessions ns or match matches es regar regardle dless ss of different technologies (eg, GPS brand), the external motion analysis system; differe different nt variable variabless (distance (distance ran ran into ▸ all trainin training/com g/competi petitive tive periods of the differe different nt velocity velocity zones vs metaboli metabolicc year year,, that that is, when when playe players rs are are with with Buchheit M. Br M. Br J Sports Med Month 2016 Vol 0 No 0
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Discussion
Figure 1 Daily distance (to (top panel) ran above 19.8 km/hour by an international player (French Ligue 1) during a 6-month period (with matches and training data integrated 5) and associated 28-day chronic and 7-day acute workloads (middle panel) and their ratio (bottom panel, with the horizontal dashed line standing for the typical ‘high-risk’ ratio of 1.5)). The player was selected with his national team to prepare for the Euro 2016 (21 May 2016 to 08 June 2016) but wasn ’t selected to participate in the � nal tournament. He then took ~3 weeks of rest before starting the preseason with his club (04 July 2016). Since the national team staff didn ’t use GPS, there are no running data available during his Euro preparation. We then assumed that during his holidays, whatever the sporting activities he practiced, he was very unlikely to reach a running speed >19.8 km/hour—high-speed load is therefore set at ‘0 distance’ for these 3 weeks. Note that in-season, national team training and competitive loads have been predicted using players ’ historical club data (based on training schedules and match playing times). As a consequence, the predicted running distance of the 4 matches played with the national team (2 per international break) are similar. While this may be seen as a limitation given the usually large (>15 –20%) match-to-match variations in high-speed running, this approach allows at least to produce the A/C ratio through these periods while avoiding erroneous spikes/drops. Finally, these data illustrate also nicely the limitation of the A/C ratio during the preseason period when no off-season data are available. With no off-season data (which differs from ‘0 distance’), chronic and acute loads are mathematically mathematically de�ned as similar for the �rst 7 training days, which results in an unrealistic A/C of 1! The use of predicted off-season data draws fortunately a much more realistic picture, with a ratio >4 at the start of the preseason, which decreases as training, and in turn � tness progresses.
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Buchheit M. Br J Sports Med Month Month 2016 Vol 0 No 0
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Discussion their clubs, with their national teams, or event eventual ually ly trai trainin ningg on their their own own during during the off-seaso off-season. n. In theory theory, this should allow a continuous tracking of load throughout the year. Despite the above mentioned arguments, and despite the lack of strong scienti �c evidenc dencee sugg sugges esti ting ng other otherwi wise se,, ther theree is a feeling that external load monitoring may be more relevant in the conte co ntext xt of injury 7 8 surveillance in elite football. 1. In fact fact,, RPE RPE is unli unlike kely ly sens sensit itiv ivee to subtle differences differences in sprinting intensity, intensity, while while this this may may be of impor importan tance ce in terms of injury risk and prevention, 3 2. RPE is someti sometime mess not even collect collected ed by national teams (scenarios 3 and 4 above above); ); the valid validity ity of sessio session-R n-RPE PE recalled on players ’ return is questionable, able, which which again again limits limits the validi validity ty and usefulness of the A/C ratio. 3. The number number of profe professi ssiona onall playe players rs able/willing to keep track of their own session-RPEs during their off-season is likely likely <5 in the entir entiree elite elite footba football ll world. To conclude, practitioners likely need to adapt a cost –bene�t approach when trying to use the A/C ratio in elite football; balancing the important efforts required to ‘get the data alright ’ (integrating the different system systems, s, variabl variables es and speed speed zones when the data data are are avail availabl able, e, predi predicti cting ng data data when when noth nothin ingg is avail vailab able le,, coll collec ecti ting ng
Buchheit M. Br M. Br J Sports Med Month 2016 Vol 0 No 0
questionable RPEs on players ’ return from intern internat ation ional al dutie duties) s) versu versuss the actua actuall output (trustability of the �nal A/C ratios and and dif dif �cult cultie iess to de�ne ‘at risk risk’ A/C thresholds in players with unknown � tness level). While the use of session-RPE as an alternative input of load may be relevant, some substantial limitations remain, such as the lack of sensitivity of RPE to subtle differen differences ces in high running speeds. The optimal duration of both the chronic (2 vs 3 vs 4 weeks, based on off-season and preseason durations) and acute (3 vs 7 days, based on matches occurrence) periods of load load need need prob probab ably ly to be disc discus usse sed d to better �t the the spec specii�c trai training/completive pattern patternss of elite elite football. football.9 Injury prevenprevention cannot be limited to the monitoring of a single single (A/C) (A/C) number; number; understa understandin ndingg players’ individual needs and pro �les, and using common common sense sense when progra programmin mmingg workload workloadss are are probabl probablyy as importan importantt to keep players � t and healthy. Twitter Follow Martin Buchheit at @mart1buch at @mart1buch
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Competing interests None declared. Provenance and peer review Not review Not commissioned; externally peer reviewed. To cite Buchheit M. Br M. Br J Sports Med Published Published Online First: [ please [ please include Day include Day Month Year] doi:10.1136/ bjsports-2016-097017 Accepted 30 October 2016
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Gabbett Gabbett TJ. The The training-in training-injury jury preven prevention tion paradox: paradox: should athletes be training smarter and harder? Br harder? Br J Sports Med 2016;50:273 2016;50:273–80. Blanch P, Gabbett Gabbett TJ. Has the the athlete athlete trained trained enough to return to play safely? The acute:chronic workload ratio permits clinicians to quantify a player ’s risk of subsequent injury. Br injury. Br J Sports Med 2016;50:471–5. Malone Malone S, Roe M, Dora Dorann DA, DA, et al . High chronic training training loads and exposure to bouts of maximal velocity running reduce injury risk in elite Gaelic football. J football. J Sci Med Sport 2016. 2016. Malone Malone S, Roe M, Dora Dorann DA, DA, et al . Aerobic � tness and playing experience protect against spikes in workload: the role of the acute: chronic workload ratio on injury risk in elite Gaelic football. Int football. Int J Sports Physiol Perform 2016:1 Perform 2016:1–25. Buchhe Buchheit it M, Allen Allen A, Poon Poon TK, TK, et et al . Integrating different tracking systems in football: multiple camera semi-automatic system, local position measurement and GPS technologies. J technologies. J Sports Sci 2014;32:1844 2014;32:1844–57. Impellizzer Impellizzerii FM, Rampinini Rampinini E, Coutts Coutts AJ, et AJ, et al . Use of RPE-based training load in soccer. Med soccer. Med Sci Sports Exerc 2004;36:1042 2004;36:1042–7. Bowen Bowen L, L, Gross Gross AS, Gimpel Gimpel M, et M, et al . Accumulated workloads and the acute:chronic workload ratio relate to injury risk in elite youth football players. Br players. Br J Sports Med 2016, 2016, Duhig Duhig S, S, Shie Shield ld AJ, AJ, Opar Opar D, et D, et al . Effect of high-speed running on hamstring strain injury risk. Br risk. Br J Sports Med 2016. 2016. Carey Carey DL, Blanch Blanch P, Ong KL, et KL, et al . Training loads and injury risk in Australian football-differing acute: chronic workload ratios in�uence match injury risk. Br J Sports Med Published Published Online First: 27 Oct 2016 doi:10.1136/bjsports-2016-096309.
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