Sports iuled 2011, 41 W); 329-3430112-lii42/ll/OC04.0329/S4996/0

© 2011 Adis Data Intofmatlon BV, All rights reserved

Strategies to Optimize Concurrent Trainingof Strength and Aerobic Fitness for Rowingand CanoeingJesús García-Pallares^'^ and Mikel Izquierdo^

1 Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Toledo, Spain2 Faculty of Sport Sciences, University of Murcia, Murcia, Spain3 Department of Health Sciences, Public University of Navarra, Pamplona, Spain

Contents

Abstract 3291, Literature Search 3312. Interference Phenomenon during Concurrent Training 3313. Concurrent Training Strategies to Minimize Interference 333

3.1 Training Periodization 3333.2 Training Volume and Frequency 3343.3 Optimal Combination of Strength and Endurance Training Intensities 3353.4 Sequence of Concurrent Training Sessions 3373.5 Number of Repetitions with a Given Load; Training to Failure versus Not to Failure 338

4, Conclusions 339

Abstract During the last several decades many researchers have reported an inter-ference effect on muscle strength development when strength and endurancewere trained concurrently. The majority of these studies found that themagnitude of increase in maximum strength was higher in the group thatperformed only strength training compared with the concurrent traininggroup, commonly referred to as the 'interference phenomenon'. Currently,concurrent strength and endurance training has become essential to opti-mizing athletic performance in middle- and long-distance events. Rowing andcanoeing, especially in the case of Olympic events, with exercise efforts be-tween 30 seconds and 8 minutes, require high amounts of maximal aerobicand anaerobic capacities as well as high levels of maximum strength andmuscle power. Thus, strength training, in events such as rowing and canoeing,is integrated into the training plan. However, several studies indicate that thedegree of interference is affected by the training protocols and there may beways in which the interference effect can be minimized or avoided. Therefore,the aim of this review is to recommend strategies, based on research, to avoidor minimize any interference effect when training to optimize performance inendurance sports such as rowing and canoeing.

330 García-Fallares & Izquierdo

Proper planning of training programme vari-ables, including intensity, frequency and volumeof exercise, is required to maximize physiologicaladaptations and to avoid overtraining in eliteathletes. This is especially important in most cy-clic sports (i.e. disciplines that require repeatedcontinuous movements similar to others such asrunning, walking, swimming, rowing, cross-countryskiing, cycling and canoeing), where both aerobicfitness and muscle strength need to be simulta-neously enhanced to optimize performance.Strength has been defined as the ability of the mus-cle to exert maximal force or torque at a specifiedvelocity.''' However, it varies for different muscleactions such as eccentric, concentric and isomet-ric. Therefore, an infinite number of values forstrength of muscles may be obtained as relatedto the type of action, the velocity of the actionand the length of the muscles. Muscle power,which is a function of the interaction between theforce applied and the speed of contraction, isassociated with the explosiveness of the muscles(i.e. the ability to develop a great deal of force ina short period of time, termed the rate of forcedevelopment).''!

On the other side, the aerobic endurance per-formance depends on two main fitness compo-nents: (i) the highest rate of oxygen consumption(VO2) attainable during maximal or exhaustiveeffort (maximal VO2 [VO2,paJ); and (ii) the an-aerobic threshold (AT): the VO2 level above whichaerobic energy production is supplemented byanaerobic mechanisms during exercise, resultingin a sustained increase in lactate concentrationand metabolic acidosis.'^! For highly trainedathletes the AT is normally placed at 80-90% ofthe VO2,,,,.

Several studies have shown the effectiveness ofconcurrent training programmes in enhancing theperformance of endurance athletes (e.g. runningeconomy, increases of the speed at lactic thresholdor improvements in the jump capability).'-^""' Pre-vious research demonstrates that both rowingand canoeing, especially in the case of Olympicevents (200, 500, 1000 and 2000 metres) with ex-ercise efforts between 30 seconds and 8 minutesrequire high levels of maximal aerobic and an-aerobic capacities, as well as maximum muscle

strength and power.''^"^"' In both sports, recentstudies found performance improvements follow-ing concurrent training programmes in highhtrained athletes, such as paddling speed and pad-dling power output at maximal and submaximalintensities, as well as lactic acid concentrations atsubmaximal intensities.''-''' '"•^-^!

Some of the mechanisms that may be re-sponsible for these improvements in performanceduring concurrent training are as follows:'-'''(i) increased strength that may improve mechan-ical efficiency, muscle coordination, and motorrecruitment patterns;'-^-''! (ii) an overall increase ofstrength that can facilitate changes and correc-tions in the technical model;'''' or (iii) increasedmuscular strength and coordination that mayreduce the relative intensity of each cycle en-abling the athlete to conserve energy.'-'"'

In recent decades, many researchers have fo-cused on studying the effects of the combinedstrength and endurance training programmes onphysical performance. The results of several stud-ies have shown that 10—12 weeks of concurren!training, with a weekly frequency between 4 and11 sessions, with intensities ranging from 60% to100% of V02max for endurance and from 40% to100% of one-repetition maximum (lRM) for resis-tance training, resulted in increases ranging from6% to 23% in V02n,ax and 22% to 38% of max-imum strength.''^"''! In the majority of thesestudies the increases in maximum strength werehigher in the group that performed only strengthtraining compared with the concurrent traininggroup. This potential conflict has been referred toas an 'interference phenomenon' because a com-promised strength development was observedwhen strength and endurance training were ap-plied concurrently.'-^! in contrast, the majority ofcurrent research supports the contention thatconcurrent training does not alter the ability topositively adapt to endurance training.'-^'^'^"'

Several studies have identified different factorsthat can influence the level or degree of inter-ference generated by concurrent training.'^''"'''''These factors include the initial training statusof the subjects, exercise mode, volume, intensityand frequency of training, scheduling of sessionsand the dependent variable being investigated.

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Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 331

In particular, the initial training status of subjectsmay play a critical role in the adaptations pro-duced by concurrent training.''*''' Most researchstudies have analysed the concurrent trainingadaptations in untrained subjects'^^-^'"''-'' or mod-erate to well trained participants.' -5.28.44-46] j ^ ^ ^ .ever, very few researchers have focused on studyingthe effects of concurrent training for elite andhighly trained athletes who require high levels ofstrength and endurance for successful performance,such as rowers and paddlers.'"•-'-'' ' This oftenrequires concurrent strength and endurance train-ing, which has become an integral part of train-ing programmes for middle- and long-distanceevents. Despite all of the experimental studies,there is a lack of practical information that en-ables coaches to design an effective training planto optimize performance in sports with high de-mands for muscle strength and aerobic fitness.Therefore, the aim of this review was to identifythe optimal combinations of training programmevariables in order to avoid or at least minimizethe negative effects of concurrent training in eliterowers and paddlers.

1. Literature Search

SciELO, Science Citation Index, NationalLibrary of Medicine, MEDLINE, Scopus,SportDiscus®, CINAHL, ProQuest, ScienceDir-ect and Google Scholar databases were searchedfrom January up to 11 April 2010 for articlespublished from original scientific investigations.Search terms included various combinations ofthe keywords 'concurrent training', 'rowing','canoeing', 'kayak', 'training periodization', 'train-ing to failure', 'training volume', 'repetitions','sets', 'resistance training', 'strength training' and"endurance training'. The names of authors citedin some studies were also utilized. Hand searchesof relevant journals and reference lists obtainedfrom articles were also conducted in the librariesof the Studies, Research and Sports Medicine Cen-ter, Government of Navarra, Pamplona, Spain.Such combinations resulted in the inclusion of89 original research articles addressing the effectsof concurrent training in elite and well trainedsubjects.

Search criteria were as follows: (i) English peer-reviewed scholarly journals only; (ii) dissertations,theses and conference proceedings were excluded;and (iii) studies must refer to the effects of con-current strength and endurance training andmanipulation of training programme variables inwell trained or highly trained athletes.

2. Interference Phenomenon duringConcurrent Training

Because strength and endurance training elicitdistinct and often divergent adaptive mechan-isms,'- -'-'* ' the concurrent development of bothfitness components in the same training regimencan lead to conflicting neuromuscular adapta-tions; as a result, different studies have foundcompromised adaptation of strength, especiallymuscle power, when both attributes were trainedat the same time as endurance." 5-27-29.36,.i7.45.48i

Although, historically, strength training hasbeen a fundamental aspect of all short-term cyclicsports, the majority of middle- and long-distancecyclic disciplines have considered resistance train-ing a potential enemy for physical performanceenhancement. Indeed, the majority of middle- andlong-distance coaches have considered strengthtraining a potential detriment to performanceand have only included it for specific parts, suchas starts and changes of pace. Most of the studieswith elite and highly trained athletes have foundinterference effects when strength and endurancewere trained concurrently (table I).

The interference of strength developmentduring concurrent training has been classicallyexplained by the following mechanisms;''*^'*''-^''(i) reductions in the motor unit recruitmentand decreases of rapid voluntary neural activa-tions;'-^-^ '**'' ' (ii) chronic depletion of muscleglycogen stores;'^^'^''' (iii) skeletal muscle fibre-type transformation from lib to lia and from liato I;l- 5-56i jy) overtraining produced by imbal-ances between the training and recovery processof the athlete;!-^--''''' and (v) decreases in the cross-sectional area of muscle fibres and in the rate ofmuscle force production'-**' due to the reductionin total protein synthesis following endurance

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332 García-Pallares & Izquierdo

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Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 333

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Leveritt et al.' ^l proposed two main reasonsfor this interference phenomenon occurring dur-ing concurrent training. First, the chronic hypo-thesis suggests that the musculoskeletal tissuecannot adapt metabolically and morphologicallysimultaneously, mainly due to differences in thetype and fibre size of the tissue when strengthtraining is carried out in isolation or combinedwith endurance training. Second, the acute hypo-thesis contends that residual fatigue produced byendurance training reduces the ability of musclesto generate force. Strength training with residualfatigue may compromise the quality of the train-ing, which may lead to a decline in strength de-velopment over a training cycle.

Because of the high demands for musclestrength and aerobic fitness in events such as row-ing and canoeing, it seems necessary to identify theoptimal combination of training variables to avoidor minimize the potential negative effects of con-current training. In light of recent studies, the fol-lowing sections will identify strategies and trainingprogrammes that have proven efTective in con-trolling potential interference eflects when strengthand aerobic fitness are developed concurrently.

3. Concurrent Training Strategies toMinimize interference

3.1 Training Periodization

Non-linear or undulating periodized resistancetraining programmes, in which short periods of highvolume are alternated with short periods of highintensity, can result in greater strength gains.l'*"^ 'Nevertheless, presently, the sequence and distribu-tion of the optimal training loads for sports in whichconcurrent training is required to achieve success incompetition, has not yet been identified.

Block periodization, the current trend in thetraining periodization for highly trained athletes,emphasizes the need to reduce the duration of thetraining phases and cycles, as well as the use ofhighly concentrated training loads focused onthe consecutive development of a minimal num-ber of motor and technical abilities.[-'•^-^•^^l Thisperiodization model has been developed in re-sponse to a number of negative effects that occur

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334 García-Pallares & Izquierdo

in elite athletes following the use of the tradition-al periodization model. This traditional modelhas been dominant for over 30 years in almost allsports and performance levels, and still remainsin force. The guidelines for this model are basedon the simultaneous development of many fit-ness components during the same training phase(e.g. aerobic capacity, maximal aerobic power[MAP], maximum strength) and, therefore, thismodel does not provide sufficient workload toenable the correct development of selected fitnesscomponents.'^''"''''''

In a recent study,'--' a 12-week periodized cy-cle of combined strength and endurance trainingwith special emphasis on prioritizing the develop-ment of two specific physical fitness componentsin each training phase (i.e. muscle hypertrophyand AT in one phase and maximum strength andMAP in the other phase), was effective for im-proving both cardiovascular and neuromuscularmarkers of top-level kayakers. In this study, ap-proximately 50% of total paddling volume duringeach phase was devoted to the development of oneendurance target. In addition, between 80-100%of the total strength training volume of each phasewas devoted to the development of one strengthtarget (figure 1).

In another study, the same group'-'' comparedtraining-induced changes in selected endurance

and performance variables following two maintraining periodization models (i.e. traditional vsblock periodization) in elite kayakers. Comparedwith traditional periodization guidelines, blockperiodization involved about half of the totaltraining volume, but with -10% higher workloadaccumulation over the selected training targets(45-60% of total training volume). The resultsdemonstrated that during short training phases.(5 weeks) block periodization resulted in a moreeffective training stimulus for the improvement ofkayaking performance (paddling spœed, stroke rateand power output) when compared with a tradi-tional approach in elite-level paddlers (figure 2).

These findings suggest that short training phases(5 weeks) using highly concentrated training loads(>50% of the total training volume) and whichfocus on the development of only two target fit-ness components in each training phase (i.e. onefor strength and another for endurance), result ina more effective training stimulus for the impro-vement of performance in highly trained athleteswhen compared with a more traditional trainingapproach.

3.2 Training Voiume and Frequency

The frequency of training may play a criticalrole in the adaptations created during concurrent

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Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 335

O ZI (%)• Z2(%)• Z3{%)

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Fig. 2. Relative contribution of each exercise intensity zone to thetotal endurance training volume performed in each phase of bothtraining periodization models (reproduced from García-Pallareset al.,l^'l with permission from Springer Science + Business f^edia).ATP, BTP and CTP = A, B and C phases of traditional periodization ap-proach; ABP, BBP and CBP=A, B and C phases of bloci< periodizationapproach; V02max = maximal oxygen consumption; VTjssecondventilatory threshold; Z1 = light intensity below second VTj; Z2 =moderate intensity between VTj and 90% of VOj^axI Z3 = high in-tensity between 90% and 100% of VOïmax-

Similarly, the total number ofweeks that athletes undergo this concurrent train-ing regimen also appears to be related to the levelof interference that is generated.i'* - **) Most ofthe studies have reported concurrent training tobe detrimental for only strength gains whentraining frequency was higher than 3 days per, eel^ [27.28,37.45.69] i^ studies where the trainingfrequency did not exceed 3 days per week, in-creases in maximum strength were detected fol-lowing concurrent training periods between 8 and16 weeks,!'5-22.67] and >20 weeks.!".-»«)

The manipulation of other variables that makeup the design of strength training such as thenumber of exercises, the number of repetitionsper set or the number of sets per exercise, is an-other widely studied issue. Several researchers haveconcluded that the strength training-induced ad-aptations, such as muscle hypertrophy or nervoussystem improvements, depend largely on the totalnumber of repetitions performed by the sub-jgj.{ [15.70-72] ¡J j jjg (jggj observed that during

strengthening programmes with trained subjects

a moderate training volume (i.e. 10 weeks with<85% of the total volume that athletes can toler-ate), is a more effective and efficient stimulus forincreasing strength than conducting a maximumor close to maximum number of repetitions in agiven training cycle.'''"•^'1

With regard to the number of repetitions per-formed per set, recent studies conducted withconcurrent training programmes in kayakers''^^and rowers''"^l showed that a moderate strengthtraining volume (approximately 50% of the maxi-mum number of repetitions that can be perfomiedin a set) were effective for increasing strength andpower. Izquierdo-Gabarren et al.'''"' found thatduring an 8-week pedodized cycle of combinedstrength and endurance training that incorporatedthree to five sets in four global and multi-jointexercises (prone bench pull, seated cable row, latpulldown, power clean) produced significant in-creases in strength, muscle power and rowingperformance in highly trained rowers. In contrast,both muscle strength and rowing performancecould be compromised if a given threshold vol-ume is surpassed or drastically reduced during ashort-term training programme. It is especially im-portant when both strength and aerobic endur-ance need to be concurrently enhanced.

To achieve optimal adaptations in musclestrength and power, as well as to minimize inter-ference phenomenon with endurance training, itis not recommended to perform a training fre-quency in excess of three strength training ses-sions per week. To maximize the strength trainingadaptations and to avoid overtraining, the opti-mal number of exercises and repetitions to per-form during each session need to be individuallyadjusted. A training volume close to 3-5 sets in4-6 specific and multi-joint exercises, during10-12 week training cycles, seems to be an ade-quate stimulus for optimal strength developmentin highly trained rowers and kayakers.

3,3 Optimal Combination of Strength andEndurance Training intensities

For a large number of sports, optimization ofphysical performance depends on the concurrentdevelopment of a small number of strength and

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336 Gareía-Pallarés & Izquierdo

endurance capabilities. Traditionally, the specificstrength improvement on rowing and canoeinghas been conducted under the guidelines of twoclassical methods: (i) local muscle endurance (LME)and hypertrophy with moderate-to-high load(i.e. 6—12RM) and high-volume, multiple-setprogrammes with short-to-moderate rest periodsbetween sets; and (ii) maximum strength andpower with high load (i.e. 1-6RM), multiple-setprogrammes with long rest periods between sets.' - 'Moreover, several research papers show that aero-bic performance in Olympic events for bothsports (rowing and canoeing) depends mainly onthe development of anaerobic threshold (AT) andVO,^,, or MAP.t'3-'^-21

Training for maximum strength (intensities >85%lRM) and maximal power (maximum powerloads) induce mainly central adaptations. Theseadaptations include improvement of the neuralcomponent through increased motor unit firingrate and changes in synchronization, recruitmentof higher threshold motor units, decreased co-contraction of antagonists and lower metabolicdemands at the muscle level.'^''' In addition, train-ing for LME and hypertrophy requires intensitiesthat range between 70% and 80% 1 RM and inducemainly peripheral adaptations. These adaptationsare highlighted by increases in the contractile pro-tein synthesis that promotes an increase in fibresize and muscle cross-.sectional area, as well as anincrease of glycolytic enzymes. However, thesetraining stimuli also produce dechnes in capillaryand mitochondrial density, as well as a consider-able metabolic and hormonal stress at the cellular

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Training intensities for MAP or VO2maconcerns aerobic endurance, induces mainly per-ipheral adaptations such as increases in mus-cle glycogen stores, capillary and mitochondrialdensity as well as an increase of oxidative en-zymes.' ''• ''•^*'' In contrast, adaptations to low andmoderate aerobic training intensity, commonlyrelated with improvements at the AT level, inducemainly central adaptations such as improvementsin pulmonary diffusion and haemoglobin affinity,as well as increases in blood volume and cardiacoutput.'-^«"'

Based on the results from these studies, Dochertyand Sporer'-^"' proposed a new model for examin-ing the interference phenomenon between endur-ance and strength training (figure 3). This modelsuggests that blending the specific training objec-tives of muscle hypertrophy for strength (LME)and MAP for endurance should be avoided(strength and power) due to these two trainingmodes inducing opposite physiological adapta-tions at the peripheral level, interferences thatprevent the body from optimally and simulta-neously adapting to both.'^^' In contrast, trainingat lower aerobic intensities (75-85% VO2max)-such as those usually employed to improve theAT, induce more central adaptations than wouldbe expected to cause much less interference withLME training. The cited model also predicts lessinterference when concurrently training for max-imum strength and power and MAP because thetraining stimulus for increasing strength wouldbe mainly directed at the neural system, not plac-ing high metabolic demands on the muscle^''"'(figure 4).

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Fig. 3. Docherty and Sporer's'^"' concurrent training modei (reproduced from Docherty and Sporer,'^"' with permission from Adis, a WoitersKluwer business [© Adis Data information BV, Ail rights reserved,]), AT = anaerobic threshold or lower endurance training intensities;LME = local muscie endurance training; MAP = maximal aerobic power; RM = repetition maximum; SPTm,, = maximum strength and powertraining; VO2ma» = nia)'i"ial oxygen consumption; î indicates Increase,

ffl 2011 Adis Data information BV, All rights resetved. Sports Med 2011,41 (4)

Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 337

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Fig. 4. Optimal combination between resistance and endurance training intensities. AT = anaerobic threshold or lower endurance trainingintensities; LME = local muscle endurance training; MAP = maximal aerobic power; SPT„,, = maximum strength and power training; î in-dicates increase; I indicates decrease.

Unfortunately, very few studies have exam-ined the effects of different concurrent trainingprogrammes in trained subjects to confirm orreject this theoretical model.'''"' de Souza et al.' **'assessed the effects of AT and MAP intensity onmaximum strength (lRM) and strength endurance(defined as the maximum number of repetitionsperformed with 80% of 1 RM) in a group of ex-perienced strength-trained athletes. The resultsshowed that a continuous low intensity andmoderate duration AT did not produce anyinterference on the subsequent strength session.Nevertheless, intermittent MAP exercise producedan acute interference effect on strength endur-ance, while maximum strength was not affectedby this aerobic exercise mode.

To the authors' knowledge, the study ofGarcia-Pallarés et al.'-^' is the first reportedpublication that examined the effects of a con-current training programme that followed theDocherty and Sporer'"'"' model in elite athletes. Inthis study, two consecutive phases (5 weeks) ofconcurrent training in elite kayakers, with specialemphasis on prioritizing the development of twospecific physical fitness components in each train-ing phase (i.e. muscle hypertrophy and AT inphase A and maximum strength and MAP in

phase B) produce great increases in maximumstrength (close to 10%), as well as increases inVOjmax (MAP) and VO2 at the second ventila-tory AT >9%.

In summary, it seems necessary to avoid thesimultaneous development of LME (8-lORM)and aerobic power, due to both training inten-sities inducing opposite adaptations on the sameperipheral components. Therefore, during a con-current training approach, endurance training atthe AT level or at lower intensities should be asso-ciated with SPT,„.,x intensities. Due to the com-patible training-induced adaptations associatedwith the MAP, LME and SPT^,,^ intensities, nointerference effects should be expected duringthe concurrent development of these fitnesscomponents.

3.4 Sequence of Concurrent Training Sessions

Several studies have highlighted the impor-tance of the sequence and timing of the aerobicand strength training sessions in order to mini-mize possible interferenceeffects.l-'''-''^'''^"*"! Thus,insufficient recovery between training sessionsmight hmit simultaneous adaptations to strengthand endurance training. Residual fatigue from a

© 2011 Adis Data Information BV. Aii rights reserved. Sports Med 2011:41 (4)

338 García-Pallares & Izquierdo

previous aerobic session could cause a reductionin the quality of subsequent strength trainingsessions by compromising the ability of the neuro-muscular system to rapidly develop force and/orreduce the absolute volume of strength trainingthat could be performed in such conditions.'^^'**''

Two studies conducted with untrained sub-jects'** '' ''' found that the order of the sessions (i.e.first strength training and then endurance train-ing or vice versa), produced no significant differ-ences in training-induced adaptations betweengroups, since both combinations allowed similarimprovements in maximum strength and MAP.Sale et al.'**"' found that concurrent strength andendurance training in untrained subjects allowedsimilar muscle hypertrophy adaptations when thestrength and endurance training sessions wereconducted on the same or on different days.Nevertheless, in this study, the strength gainswere significantly higher in the group that per-formed the training sessions on different days.Similarly, in well trained athletes,'**'' following anaerobic endurance training session, strength per-formance remained significantly decreased for atleast 8 hours after completion of the endurancesession. In a recent study,''-' highly trained kaya-kers achieved significant improvements in aero-bic power, and maximum strength and musclepower by placing the strength sessions before theendurance sessions or. when not feasible, sepa-rating both types of training sessions by at least6-8 hours to allow for restoration and glycogenrepletion.

From a similar point of view, several studieshave detected interference in strength gains dur-ing concurrent training only when the same musclegroups were used for both resistance and en-durance training.'-"'''*'' As already addressed insection 3.3, aerobic training intensities not ex-ceeding AT produce mainly central adaptations.This is a critical success factor for Olympic row-ing and canoeing, due to improvements in pul-monary diffusion and haemoglobin affinity, aswell as increases in blood volume and cardiacoutput.'"' By conducting extra endurance train-ing sessions at submaximal AT intensities and bynot involving specific muscle groups (e.g. cyclingfor paddlers), this may allow high-level athletes

to obtain the aforementioned central adapta-tions, as well as an increase of the total trainingvolume at submaximal AT intensities and an en-largement of the recovery periods between train-ing sessions. In contrast, performing endurancetraining sessions at MAP or supramaximal in-tensities (anaerobic metabolism) on non-specificmuscle groups is not recommended. This trainingintensity will mainly induce peripheral adapta-tions on muscle groups that will not have a deci-sive role in the competitive technique model.

In summary, the residual fatigue caused by aprevious endurance session could reduce and/orimpair the quantity and quality of subsequentstrength training sessions. Therefore, it seems rea-sonable to suggest a strict knowledge of therecovery periods between training sessions; in par-ticular, for highly trained athletes, the strengthtraining sessions should be placed before the en-durance sessions or at least separating both typesof training sessions by more than 8 hours. Perform-ing extra endurance training sessions at submaxi-mal intensities and employing mainly non-specificmuscle groups, may allow high-level athletes toachieve central adaptations, while the specificmuscle groups recover for subsequent sessions ofgreater intensity.

3.5 Number of Repetitions wWh a Given Load:Training to Faiiure versus Not to Failure

The number of repetitions performed with agiven load may impact the extent of muscle dam-age and cause subsequent decrements in velocityand force production.''*^''*^' Thus, the role oftraining leading to repetition failure (inability tocomplete a repetition in its full range of motion)has been of interest to coaches and sport scien-tists, in order to understand the physiologicalmechanisms underlying training-induced gains instrength and power. Most of these researchershave focused on studying the mechanisms andeffects that training leading to repetition failurehave on muscle strength and power, as well as theeffects on the athlete's performance.'' '**''"**' '

Short-term training (<9 weeks) leading to 're-petition failure' produces greater improvementsin strength when compared with a 'not to repeti-

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Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 339

tion failure' training approach in trained sub-jects.'**'** ! However, other studies have concludedthat training to repetition failure may not benecessary for optimal strength gains, since theincurred fatigue reduces the force that a musclecan generate.'** ** - **' Several factors, such as dif-ferences in the manipulation of volume and in-tensity of training, dependent variable selection,muscle groups involved and initial training statusof the subjects, may explain the contradictoryresults of these studies.

In previously resistance-trained men, it hasbeen reported that when the volume and intensityvariables were equated, training not leading torepetition failure led to similar improvements inmaximum strength and muscle power output'**^!(figure 5).

In highly trained male rowers,''^1 an 8-week,linear-periodized, concurrent strength and endur-ance training programme, using a moderate num-ber of repetitions not to repetition failure, provideda favourable environment for achieving greaterenhancements in strength, muscle power and row-ing performance when compared with higher train-ing volumes of repetition to failure (figure 6).

Likewise, in two studies performed with elitekayakers and with concurrent training, a peri-odized training cycle of 12 weeks''^' and a pre-

competitive training phase of 47 weeks' - ' allowedpaddlers to achieve great improvements in max-imum strength and power when a not to repeti-tion failure training approach was employed.

In summary, a concurrent strength and en-durance training programme using a moderatenumber of repetitions for not to repetition failuretraining provides a favourable environment forachieving greater enhancements in strength, mus-cle power and specific performance when com-pared with higher training volumes of repetitionto failure. The training for the not to repetitionfailure approach speeds up recovery from strengthtraining, allowing rowers and paddlers to executesubsequent endurance training sessions with a su-perior performance.

4. Conclusions

Several strategies or mechanisms have proveneffective in reducing the interference phenome-non of concurrent strength and endurance train-ing, especially in rowing and canoeing where bothcapabilities need to be developed simultaneouslyto optimize performance as follows:• Short training phases (5 weeks) using highly

concentrated training loads (>50% of the totaltraining volume) focusing on the concurrent

NRF Control

Fig. 5. (a) Maximal paraliel squat strength; and (b) parallel squat muscle power during the experimental period (reproduced from Izquierdoet al..l^^l with permission from The American Physioiogicai Society). 1 RM = one-repetition maximum; NRF = not to repetition faiiure group;RF = repetition to faiiure group; TO = timepoint hefore training; T1 =timepoint after 6 wk of training; T2 = timepoint after 11 wk of training;T3 = timepoint after 16 wk of training. * p < 0.05 from the corresponding timepoint TO; " p < 0.05 from the corresponding timepoint T1 ; t p < 0.05from the corresponding timepoint T2; t p< 0.05 from relative change at timepoint T2 between the groups.

it) 2011 Adis Data Information BV. Aii rights reserved. Sports Med 2011. 41 (4)

340 García-Pallares & Izquierdo

700 1

600 -

•:; 5 0 0<o

Pre-post 1 4

Weeks

• RFe NRF• Control

r 2 0

• 1 5

• 1 0

0 03

-5

mU

L - 1 0

Fig. 6. Changes in muscle power output with an absolute load corresponding to 70% of one-repetition maximum (1RM) in bench pull duringthe experimental period (reproduced from Izquierdo-Gabarren et ai.,''^' with permission from Lippincott Wiiliams and Wilkins). NRF = not torepetition faiiure group; RF = repetition to faiiure group; * p < 0.05 from wk 1 ; " p < 0.05 from corresponding vaiue of RF.

development of one strength and one endur-ance target, can provide a more effective train-ing stimulus for the improvement of performancein highly trained athletes when compared witha traditional training approach.Three strength training sessions per week seemsto be an optimal stimulus to achieve positiveadaptations in muscle strength and power, aswell as to minimize the interference phenomenonwith endurance training in high-level athletes.To maximize the strength training adapta-tions and to avoid overtraining, the optimalnumber of exercises and repetitions performedduring each session need to be individuallyadjusted. A training volume close to 3-5 sets in4-6 specific and multi-joint exercises, during10-12 weeks of training cycles, seems to be anadequate stimulus for an optimal strength devel-opment in highly trained rowers and kayakers.Avoidance of the simultaneous developmentof LME (8-10 RM) and aerobic power canreduce the interference phenomenon due toboth training intensities inducing opposite ad-aptations on the same peripheral components.

In contrast, due to the compatible training-induced adaptations associated with strengthand power and aerobic power, as well as thecompatible effects of MAP, LME and strengthand power intensities, no interference effectsshould be expected during the concurrentdevelopment of these fitness components.The residual fatigue caused by a previousendurance session could reduce and/or impairthe quantity and quality of subsequent strengthtraining sessions; in particular, for highlytrained athletes, the strength training sessionsshould be placed before the endurance ses-sions, or at least separating both types of train-ing sessions by more than 8 hours. Performingextra endurance training sessions at submaxi-mal intensities that involve mainly non-specificmuscle groups, may allow high-level athletesto achieve muscle peripheral adaptations,while the specific muscle groups recover forsubsequent sessions of greater intensity.The training to repetition failure approachshould be avoided in athletes at any performancelevel. A concurrent strength and endurance

© 2011 Adis Data Information BV, All rights reserved. Sports Med 2011; 41 (4)

Concurrent Strength and Aerobic Fitness Training for Rowing and Canoeing 341

training programme using a moderate numberof repetitions for not to repetition failure train-ing provides a favourable environment forachieving greater enhancements in strength,muscle power and specific performance whencompared with higher training volumes ofrepetition to failure. The training for the not torepetition failure approach speeds up recoveryfrom strength training, allowing rowers andpaddlers to perform subsequent endurancetraining sessions of higher quality.

Acknowiedgements

No sources of funding were used to assist in the prepara-tion of this review. The authors have no conflicts of interestthat are directly relevant to the content of this review.

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Correspondence: Dr Jesús García-Paltarés, Apartado 81,30720 Santiago de la Ribera, Murcia, Spain.E-mail; jesus.garcia.pallares@gmail.com

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