Sports Med 2006; 36 (10): 817-828LEADING ARTICLE 0112-1642/06/0010-0817/$39.95/0

2006 Adis Data Information BV. All rights reserved.

Psychomotor SpeedPossibly a New Marker for Overtraining Syndrome

Esther Nederhof,1,2 Koen A.P.M. Lemmink,1,2 Chris Visscher,1,2 Romain Meeusen3 andTheo Mulder1,2

1 Center for Human Movement Sciences, University Medical Center Groningen, University ofGroningen, Groningen, The Netherlands

2 University Center for Sport, Movement and Health, University Medical Center Groningen,Groningen, The Netherlands

3 Department of Human Physiology and Sports Medicine, Free University of Brussels,Brussels, Belgium

Overtraining syndrome (OTS) is a major threat for performance and health inAbstractathletes. OTS is caused by high levels of (sport-specific) stress in combinationwith too little regeneration, which causes performance decrements, fatigue andpossibly other symptoms. Although there is general consensus about the causesand consequences, many different terminologies have been used interchangeably.

The consequences of overreaching and overtraining are divided into threecategories: (i) functional overreaching (FO); (ii) non-functional overreaching(NFO); and (iii) OTS. In FO, performance decrements and fatigue are reversedwithin a pre-planned recovery period. FO has no negative consequences for theathlete in the long term; it might even have positive consequences. Whenperformance does not improve and feelings of fatigue do not disappear after therecovery period, overreaching has not been functional and is thus called NFO.OTS only applies to the most severe cases. NFO and OTS could be preventedusing early markers, which should be objective, not manipulable, applicable intraining practice, not too demanding, affordable and should be based on a soundtheoretical framework. No such markers exist up to today. It is proposed thatpsychomotor speed might be such a marker.

OTS shows similarities with chronic fatigue syndrome and with major depres-sion (MD). Through two meta-analyses, it is shown that psychomotor slowness isconsistently present in both syndromes. This leads to the hypothesis that psycho-motor speed is also reduced in athletes with OTS. Parallels between commonlyused models for NFO and OTS and a threshold theory support the idea thatpsychomotor speed is impaired in athletes with NFO or OTS and could also beused as an early marker to prevent NFO and/or OTS.

In the past 20 years, the overtraining syndrome of the majority of research and review articles has(OTS) has received much attention from researchers been on the prevention of OTS. However, no relia-and practitioners because it is a serious threat for ble marker for the early detection of OTS has beenathletic performance and health. The primary focus described so far. Therefore, the goal of the present

818 Nederhof et al.

article is to propose a possible new marker for OTS the overreaching has no detrimental effects in theusing a multidisciplinary approach. long term, and in many cases even has positive

effects, this kind of overreaching is termed ‘func-1. Terminology tional’.

In NFO, the overload training does have detri-Before proceeding with reviewing the methodsmental effects in the long term. Full recovery doesthat have been developed for the early detection ofnot take place within the pre-planned period of time.OTS, current terminology in the field will be dis-This is undesirable because of two reasons. First, acussed because many different terms have been usedrecovery period that takes longer than planned mightfor the same concept.[1-5] In North American litera-interfere with competitions. A second problem thatture, the term ‘staleness’ is mostly used for thecan occur with NFO is deconditioning due to theproblem that is termed ‘overtraining syndrome’ orlonger recovery period. Therefore, this kind of over-just ‘overtraining’ in the European literature. Otherreaching is non-functional.terms that have been used for this phenomenon are

When a state of deteriorated performance and‘failure adaptation’, ‘underrecovery’, ‘trainingfatigue goes together with clinical symptoms, whilestress syndrome’ and ‘unexplained underperfor-other pathological causes have been ruled out, wemance syndrome’.[6-9] Recently, Kellmann[10] pro-speak of OTS. Clinical symptoms might includeposed to integrate the North American and the Euro-depression, eating disorders, sleeping disorders andpean terminologies. In his proposal, the termshormonal deviations.[11-13] Although some signs and‘short-term overtraining’ and ‘overreaching’ shouldsymptoms, such as depressed mood, concentrationbe used synonymously and as verbs. ‘Long-termproblems, eating disturbances or sleeping problems,overtraining’ should be used synonymously withmight also be present in NFO athletes, this state‘overtraining’ and both should be used as verbs.should be differentiated from OTS by the absence of‘Overtraining syndrome’ is the term Kellmann[10]

pathophysiological symptoms. Also, the time that isproposes to use for the negative outcome of long-needed for recovery is different. Recovery fromterm overtraining.NFO might require some weeks or months of rest,However, based on practical and clinical obser-whereas for recovery from OTS months to years arevations as well as on scientific evidence, the authorsneeded. Thus, the main difference with the terminol-of the present article conclude that there must be anogy as proposed by Kellmann[10] is the distinctionadditional category between the two categoriesbetween FO and NFO and the fact that only the mostKellmann[10] proposed (e.g. overreaching and over-severe cases will experience OTS. This idea is sup-training). We propose to divide the outcome ofported in a consensus statement of the Europeanoverload training into the following three catego-College of Sport Science.[14]

ries: (i) functional overreaching (FO); (ii) non-func-tional overreaching (NFO); and (iii) overtraining 2. Prevalence of Overtrainingsyndrome (table I). Syndrome (OTS)

FO will be used for a temporary state of perform-ance decrements and fatigue, which is reversed Estimates of the prevalence of OTS should bewithin a pre-planned period of time. FO usually reconsidered in the light of the new terminology. Itoccurs after a period of overload training. Because has been estimated that between 20% and 60% of

Table I. Summary of the different terminology used

Old terminology New terminology Symptoms Recovery

Short-term overtraining or Functional overreaching Mild Days to weeksoverreaching

Long-term overtraining or Non-functional overreaching Moderate Weeks to monthsovertraining syndrome Overtraining syndrome Severe Months to years

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

Psychomotor Speed in Overtraining Syndrome 819

Table II. Overview of non-functional overreaching (NFO) and/or overtraining syndrome (OTS) case studies between 1995 and 2005

Study No. of Diagnosis by Duration of Severity of symptoms Duration of Status accordingsubjects authors symptoms recovery to new definition

Gouarne et al.[22] 2 OTS 6mo min. ND ND NFO or OTS

Meehan et al.[11] 5 OTS 4mo – 2y Moderate to severe ND NFO or OTS

Meeusen et al.[12] 1 OTS Several months Severe 1y OTS

Mourot et al.[23] 7 OTS ND ND A period of either NFO or OTSrest or bedrest

Rowbottom et al.[24] 10 OTS 6mo ND A period of either NFO or OTSrest or bedrest

Uusitalo et al.[13] 1 OTS 3mo min. Severe ND OTS

min. = minimum; ND = has not been described in the publication.

athletes experience the negative effects of overtrain- be argued that OTS may occur much less frequentlying at least once during their career.[3] These figures than the previously proposed percentages.have partly been determined by surveys with ques- It is possible that case studies presented on OTStions such as if participants “had experienced a give more insight into the prevalence, therefore, asignificant performance decrement that persisted for literature search was conducted. The authors identi-at least two weeks, and that without any doubt was fied six case studies of athletes with OTS that werecaused by too much physical training.”[15] Such published between 1995 and 2005.[11-13,22-24] A totalquestions may reveal something about the preva- of 26 cases were presented (table II). In 24 of theselence of NFO but not about the number of athletes cases, presented in four different studies, it could notwho have experienced OTS. be concluded whether it was OTS or NFO.[11,22-24] In

these studies it was noted that all subjects exper-Other evidence for the over-estimated frequencyienced OTS- and NFO-related symptoms, but theof OTS occurrence comes from studies in whichseverity of the symptoms and/or the duration of theathletes were followed during a regular season. Forrecovery period have not been described. It is impor-example, Hooper et al.[16] followed 14 swimmerstant to report both the severity of the symptoms andduring 6 months. They found that 21% of the swim-the recovery period the athletes needed to be able tomers were overtrained at some point during thedistinguish NFO from OTS. The other two casesstudy. However, the criteria Hooper et al. used dopresented did probably experience OTS as theynot make a distinction between NFO and OTS: oneshowed symptoms at clinical levels and/or showedof their criteria for OTS was high fatigue for at leastmarked hormonal deviations and/or needed 1 year of7 days and no other pathological causes for thisrest to recover.[12,13] Thus, it must be concluded thatfatigue. Similar percentages were found in otherprevious estimations were probably too high. Itstudies,[17,18] but again no clear distinction can beseems that NFO is a much more frequently occur-made between NFO and OTS on the basis of thesering state than OTS. Previous estimations of a preva-publications. Urhausen et al.[19,20] and Gabriel etlence of 20–60% seem more correct for NFO thanal.[21] monitored 17 endurance athletes (cyclists andfor OTS.triathletes) over approximately 18 months. They

purposefully overloaded the athletes to induce(N)FO, which succeeded in 13 cases. Only two 3. Causes of Non-Functionalcases of non-purposefully induced (N)FO occurred. Overreaching and OTSNo report of undesirably long recovery periods hasbeen made[19] indicating that, according to the new NFO and OTS are caused by high stress in com-terminology, OTS did not occur. Thus, no conclu- bination with inadequate regeneration.[12,25,26] Physi-sions about the prevalence of OTS can be drawn in cal stress is seen as the most important cause of NFOthe light of this new terminology. It can, however, and OTS, although current insights point toward

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

820 Nederhof et al.

physiological stress in combination with psycholog- ment. In other words, personal disposition can beseen as a relevant modifier of individual stress ca-ical and/or social stressors in relation to regenera-pacities. The more favourable one’s disposition, thetion.[11,16,27,28] Thus, an athlete who experiences highmore stress one can handle. Support for this idea haslevels of stress, such as occupational stress, is at aalso been presented in case studies of NFO andhigher risk for NFO or even OTS than a similarOTS.[11,18]athlete under the same training regimen with low

occupational stress. Also, sudden changes in stres-4. Early Detectionsors, for example the death of a significant other, can

increase the risk for NFO and OTS substantially,Since the only effective cure for NFO and OTS iseven though the training load may remain the same.

(complete) rest for several weeks or months (up toIn their model, Kentta and Hassmen[27] stated that years in the case of OTS) it is desirable to prevent it

not only the amount of stress and regeneration an by monitoring different markers of NFO and/orathlete experiences is important in the development OTS. It is argued here that usable markers for NFOof NFO and OTS but also the individual stress and/or OTS should fulfil six criteria. They shouldcapacity. This stress capacity consists of physical, be: (i) objective; (ii) not manipulable; (iii) applica-psychological and social capacities that can all buff- ble in training practice; (iv) not too demanding forer stress.[27] This idea is very similar to the threshold athletes; (v) affordable for the majority of athletes;theory, which explains inter-individual differences and (vi) the selection of the markers should be basedin functional impairment after brain lesions.[29]

on a sound theoretical framework.Satz[29] stated that functional impairment only oc- Until today no reliable markers that fulfil thesecurs when a brain lesion, or another disease, takes six criteria have been identified (for extensive recentaway more of the reserve capacity than is minimally reviews see Halson and Jeukendrup,[1] Platen[31] andneeded for normal functioning. Thus, the decisive Urhausen and Kindermann[32]). Several reasons forfactor for the occurrence of functional impairment is inconsistent findings can be identified. The firstnot the size of a brain lesion or the stage of the problem in this field is the definition of overreach-disease but the reserve capacity that is still availa- ing and overtraining.[1,2,10,14,33] Another problem isble.[29] In athletes, not the absolute training load but that performance has not always been assessed.[1,31]

the combination of total stress, total regeneration As the existence of FO, NFO or OTS is defined byand total capacity is the decisive factor for the the presence of performance decrements, this shouldoccurrence of NFO and/or OTS.[27]

be seen as a major weakness of overreaching andAttempts to explain inter-individual differences overtraining research. An additional source of varia-

in susceptibility to NFO and OTS are not new. In bility in research findings is the fact that markers1988, Anderson and Williams[30] presented a model have been studied under different circum-in which psychosocial variables predicted injuries. stances.[31,32] For example, hormonal parametersSpecifically, history of stressors, personality charac- might behave differently during rest or after stress

tests.[12,34] Hormonal parameters should also beteristics and coping resources were seen asmeasured under highly standardised conditions,[35]predictors of injury. A similar idea was presented bywhich might not always have been the case (seeTenenbaum et al.[9] in 2003. Their stress-responseTremblay et al.[31]). However, the purpose of themodel indicated how it is possible that differentpresent article is not to review existing research butathletes perceive the same stressors differently. Theto propose a new marker: psychomotor speed.perception of a stressor is mediated by personal

disposition. For example, an athlete who exper- Psychomotor speed might be a relevant variableiences a lot of social support might perceive chal- for the early detection of NFO and OTS. This argu-lenges in competition differently than an athlete who ment is based on the substantial overlap betweenmainly feels pressure from his/her social environ- OTS on the one hand and chronic fatigue syndrome

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

Psychomotor Speed in Overtraining Syndrome 821

(CFS) and major depression (MD) on the other differences in hormonal reactions on stress tests,hand, which will be further explored in section 5. It such as exercise tests, have been found betweenis well known that psychomotor speed is reduced in healthy subjects and patients with both CFS[46] andpatients with many different pathologies such as OTS.[12]

type 2 diabetes mellitus,[36] Parkinson’s dis- There also seems to be altered immune functionease,[37,38] Alzheimer’s disease[39] and HIV.[40] Be- in both CFS[43,44,47] and OTS,[32] although the num-cause there are more similarities between OTS and ber of studies conducted in the field of CFS is muchMD and between OTS and CFS than between OTS larger than the number of studies conducted in theand the aforementioned pathologies, the nature of field of OTS. The same is true regarding the auto-psychomotor slowness in MD and CFS will be ex- nomic nervous system. Although studies into auto-tensively explored in section 6. Preliminary evi- nomic nervous system functioning in OTS (e.g.dence for the existence of psychomotor speed in heart rate variability) look promising,[23,48] notathletes with a disturbed stress regeneration balance enough studies have been published in the field ofwill be presented in section 7. OTS to confirm similarities with CFS.[43,49]

Another disorder that shows marked similaritieswith OTS is MD. Armstrong and VanHeest[50] de-5. OTS and Related Syndromesscribed several characteristics that MD and OTS

The possible relationship between OTS and CFS have in common. The initiating factors as well as thewas first described more than a decade ago by Fry et factors that influence the symptoms in MD and OTSal.[41,42] and more recently by Shephard.[43,44] The are partly the same. MD can occur after the occur-only case evidence for this relation was given by rence of a negative life event, which has also beenRowbottom et al.[24] who reported that athletes diag- reported in OTS. The two syndromes also sharenosed with OTS also fulfilled the criteria for CFS. symptoms such as disturbed mood states, impairedIndeed, criteria for CFS largely overlap the com- mental and physical performance, altered balance ofmonly mentioned symptoms for OTS.[41,42] CFS is the autonomic nervous system and dysfunctions inmainly characterised by debilitating fatigue, which neuroendocrine systems. In both MD and OTS, ais also common in OTS. Other symptoms that CFS change in HPA axis function has been seen, as welland OTS have in common are mainly neuropsycho- as changes in the sympathetic-adrenal medullar axis.logical symptoms such as inability to concentrate, Consequently, Armstrong and VanHeest[50] suggest-depression, irritability and difficulty thinking, but ed that MD and OTS might be controlled by thealso sleep disturbances are a common symptom. same mechanisms.However, this does not mean that OTS and CFSfully overlap or that OTS can “be classified as a 6. Psychomotor Slowness in Patients with‘chronic fatigue syndrome condition’”,[42] because Major Depression and Chronicmost athletes who are suspected of OTS do not fulfil Fatigue Syndromeall criteria for CFS.[45]

Other similarities between OTS and CFS are Some years ago, White et al.[51] performed aendocrinological abnormalities due to hypothalam- meta-analysis on psychomotor slowing in patientsic-pituitary-adrenal (HPA) axis dysfunction. Al- with MD. They performed a systematic literaturethough CFS and OTS have never been studied to- search in PsychINFO and MEDLINE for journalgether, similar abnormalities are present. For exam- articles published between 1984 and 1996 that in-ple, in both CFS and OTS slightly altered resting cluded tasks of psychomotor speed in patients withlevels of cortisol, ACTH and other HPA axis-associ- MD. A total of 11 journal articles met the criteriaated hormones are found (see Urhausen and Kinder- that patients were included according to Diagnosticmann[32] for a review of findings in OTS; see and Statistical Manual of Mental Disorders (DSM)Cleare[46] for a review of findings in CFS). Also, III or DSM III-R criteria and that the mean ages of

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

822 Nederhof et al.

the MD and control groups were within 10 yearsfrom each other. They found that in all studiesreaction times were significantly slower in the MDgroups compared with the control groups.[51]

In their meta-analysis, White et al.[51] performeda regression analysis to answer the question: whatwere “the relative contributions of sensory/motorand cognitive deficits to psychomotor slowing?”Regression equations explained 99% of the variancewith a slope of 1.26, meaning that patients with MDwere 26% slower than control subjects. Because theintercept did not differ significantly from zero,White et al.[51] concluded that motor and cognitivespeed were lowered to about the same degree inMD.

To show that this result is still currently robust,the authors of the present article conducted a similarmeta-analysis with journal articles published be-tween 1997 and 2005. Articles were searched inEMBASE, PsychINFO and MEDLINE with thesame search strategy as employed by White et al.[51]

Keywords were: ‘reaction time’, ‘reaction speed’,‘response time’, ‘response speed’, ‘processingtime’, ‘processing speed’, ‘psychomotor time’,‘psychomotor speed’, ‘psychomotor slow*’, ‘cogni-tive speed’, or ‘cognitive slow*’ in combinationwith the word ‘depression’ in the title. Abstractsfrom the listed articles were examined. Only articlesthat gave exact data on reaction times of a group ofMD patients (diagnosed according to DSM III-R orDSM IV criteria) and a group of healthy controls ofwhich the mean ages were <10 years apart wereselected. Studies in which only part of the reactiontime was studied (e.g. only processing time or onlymovement time) were not included. A total of 13published articles met the criteria (table III).[52-64]

Results of the currently reviewed studies wereanalysed in the same way as the results in the Whiteet al.[51] meta-analysis. Studies in the present meta-analysis never contained more than two differentreaction time tasks. In those studies where depressedpatients were compared with control subjects on twotasks, only the results of the most difficult task (i.e.with the longest reaction times) were included in theanalysis. Reaction times of MD patients were plot-

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

Tab

le I

II. S

umm

ary

of s

tudi

es in

clud

ed in

met

a-an

alys

is r

eact

ion

times

of

depr

esse

d pa

tient

s an

d he

alth

y co

ntro

l sub

ject

s

Stu

dyN

o. o

f su

bjec

tsM

ean

age

(y)

Tas

kS

timul

us/r

espo

nse

depr

esse

dco

ntro

lde

pres

sed

cont

rol

Aus

tin e

t al

.[52]

7728

5160

Cho

ice

reac

tion

time

No

info

rmat

ion

Ban

ge a

nd B

athi

en[5

3]12

2050

51In

hibi

tion

reac

tion

time

task

Vis

ual/m

anua

l

Bon

in-G

uilla

ume

et a

l.[54]

1616

7980

Cho

ice

reac

tion

time

Vis

ual/m

anua

l

Con

stan

t et

al.[5

5]20

2648

49S

impl

e re

actio

n tim

eV

isua

l/man

ual

Ege

land

et

al.[5

6]50

5035

33S

eque

ntia

l rea

ctio

n tim

e te

stV

isua

l/man

ual

Gar

cia-

Tor

o et

al.[5

7]40

2042

39V

ocal

rea

ctio

n tim

eA

udito

ry/v

erba

l

Har

t et

al.[5

8]7

1167

70C

ontin

uous

per

form

ance

tes

tV

isua

l/man

ual

Hug

dahl

et

al.[5

9]12

1233

31M

enta

l arit

hmet

ic t

ask

Vis

ual/m

anua

l

Ort

iz-A

lons

o et

al.[6

0]15

1564

60In

hibi

tion

reac

tion

time

task

Vis

ual/m

anua

l

Rog

ers

et a

l.[61]

910

5750

Men

tal r

otat

ion

Vis

ual/m

anua

l

Sw

eene

y et

al.[6

2]58

5132

36B

ig c

ircle

/littl

e ci

rcle

Vis

ual/m

anua

l

Tso

urto

s et

al.[6

3]20

2039

36In

spec

tion

time

Vis

ual/m

anua

l

Vol

lmer

-Con

na e

t al

.[64]

2121

3634

Sho

rt-t

erm

mem

ory

task

No

info

rmat

ion

Psychomotor Speed in Overtraining Syndrome 823

ted against reaction times of healthy controls (figure were found that compared the reaction times of CFS1). A linear regression line was fitted through the patients with healthy controls. In two of the sevendata. The slope of the regression line was 1.20 with studies that fulfilled all criteria, the control groupthe line through the origin and R2 = 0.96. This was exactly the same and the CFS group of onemeans that MD patients were 20% slower than con- study was a selection of patients from the othertrol subjects. study.[67,68] Therefore, only the first published study

was included in this meta-analysis. Hence, a total ofAn identical procedure was followed for the reac-six studies could be included in the analysis (tabletion times of CFS patients. This was done to makeIV).[68-73]psychomotor slowness of MD and CFS patients

Only one task was used in the analysis for eachcomparable and because the above-describedstudy. In studies that used two or more differentmethod has shown to be useful and transparent.tasks, only the task with the longest reaction timesArticles published from 1995 to 2004 were searchedwas included in the analysis. In case of more condi-in EMBASE, PsychINFO, and MEDLINE with thetions per task, only the condition that produced thesearch terms ‘reaction time’, ‘reaction speed’, ‘re-middle longest reaction times was used. Reactionsponse time’, ‘response speed’, ‘processing time’,times of CFS patients were plotted against reaction‘processing speed’, ‘psychomotor time’, ‘psycho-times of healthy controls (figure 2). A linear regres-motor speed’, ‘psychomotor slow*’, ‘cognitivesion line was fitted through the data. The slope ofspeed’, or ‘cognitive slow*’ in combination withthe regression line was 1.15 with the line through the‘chronic fatigue syndrome’. Only articles in whichorigin and R2 = 0.84. This means that MD patientsCFS patients were included according to clear crite-were 15% slower than control subjects. The lowerria such as the criteria described by Fukuda et al.[65]

R2 in this meta-analysis compared with the meta-or Sharpe et al.[66] were used in the analysis. Patientsanalysis with MD patients in this article as well as inhad to show signs and symptoms of CFS for at leastWhite et al.’s[51] article is partly due to the small6 months and the mean age of CFS patients andamount of studies that were included. Part of thehealthy controls should be <10 years apart. As in thelower R2, however, might also be sought in the largeprevious meta-analysis, studies in which only a partdifferences in the numbers of participants in theof the reaction time was given (e.g. only processingdifferent studies. A study with many participantstime or only movement time) and articles that didgives more reliable results but has a relatively small-not give precise information on reaction times (e.g.er influence on the analysis than studies with lesseronly presented data in a graph) were excluded fromparticipants. Nevertheless, it can be concluded thatthe analysis. Using these criteria, only seven articlesCFS patients show a consistent psychomotor slow-ness, a conclusion that is consistent with the conclu-sion drawn in earlier review articles.[74,75] Consider-ing the similarities between MD, CFS and OTS, it ishypothesised that psychomotor speed is also im-paired in overtrained athletes.

7. Measurement of Psychomotor Speed

The hypothesis that psychomotor speed is re-duced in athletes with OTS has a high face validitybecause overtrained athletes regularly report symp-toms such as concentration problems, cognitivecomplaints and memory problems.[11,22,24] Addition-ally, computerised tests of psychomotor speed fulfil

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Reaction times healthy controls (ms)

Rea

ctio

n tim

es M

D p

atie

nts

(ms)

Fig. 1. Reaction times of healthy controls plotted against reactiontimes of patients with major depression (MD).

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

824 Nederhof et al.

Table IV. Summary of studies included in meta-analysis reaction times of patients with chronic fatigue syndrome (CFS) and healthy controlsubjects

Study No. of subjects Mean age (y) Task Stimulus/response

CFS control CFS control

Chiaravalloti et al.[68] 45 29 42 37 Choice reaction time Auditory/manual

Fiedler[69] 18 18 40 45 Continuous performance test Visual/manual

Lawrie et al.[70] 30 15 44 41 CANTAB No information

Marshall et al.[71] 20 20 36 36 Choice reaction time Visual/manual

Michiels et al.[72] 29 22 40 40 Cued reaction time Visual/manual

Smith et al.[73] 67 126 42 40 Repeated digit detection Visual/manual

CANTAB = Cambridge Neuropsychological Test Automated Battery.

all six criteria for early markers for NFO and OTS. healthy athletes on the amount of mistakes made onBecause assessment is computerised, it is objective the Stroop Color Word Test.[81]

and not manipulable. Furthermore, a task that can be The second study is a case study of an athleteperformed in a quiet room on a laptop can easily be with NFO who was diagnosed according to theintegrated into a training programme. Single train- Meeusen et al.[12] protocol.[82] The athlete with NFOing sessions do not have detrimental effects on com- was compared with a group of healthy athletes of theplex reaction time performance when assessed after same age and sport on the Vienna Determinationphysical exercise.[76-80] Also, computerised assess- Test. This test of psychomotor speed consisted ofment techniques are affordable, making the mea- two conditions, one self-paced condition and onesurement of psychomotor speed a suitable method auto-paced condition in which subjects are put underfor regular monitoring in order to prevent develop- pressure. Only in this last condition a difference wasment of NFO and/or OTS. found between the athlete with NFO and the healthy

athletes.[82] The authors once again want to stress theThe most important step that needs to be taken inimportance of reporting severity of the symptomsthe development of psychomotor speed as a markerand the recovery period that was needed.for NFO and/or OTS is determining the threshold

beyond which athletes are at risk. The authors of the The disadvantage of these two methods is thepresent article are convinced that research should be cross-sectional nature. Another research paradigmconducted using different paradigms over the full that does not have this disadvantage is a prospectivetraining continuum. model in which athletes are assessed at different

times during the athletic season.[83] Using thisFirst, healthy athletes can be compared with un-method it is possible to assess normal seasonal vari-derperforming athletes. The authors of the presentation as well as to compare well trained athletes witharticle are aware of two such studies. Hynynen etathletes who overtrained resulting in NFO or possi-al.[81] compared 12 overtrained athletes to 12 healthybly even OTS. For as far as the authors know,athletes of the same sex and age on the Stroop Colorpsychomotor speed has never been assessed in aWord Test. The overtrained athletes experiencedprospective training study. For the development ofunderperformance even after a recovery period of atearly markers, such as psychomotor speed, theseleast 3 weeks, all athletes had a training history thattypes of studies are highly valuable because of theircould likely be the cause of underperformance andprospective nature. It is therefore of great impor-other pathology had been ruled out. In the light oftance to conduct these studies.our new terminology it cannot be decided if these

athletes experienced NFO or OTS as no information The next research paradigm that should be ap-about the severity of the symptoms and about the plied is the study of the effect of overload training. Iflength of the recovery period is given. Still, a differ- psychomotor speed is indeed reduced in athletesence was found between the NFO/OTS and the with NFO and/or OTS, this does not make psycho-

2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (10)

Psychomotor Speed in Overtraining Syndrome 825

motor speed into an early marker. To show the Nederhof et al.[84] tested cyclists before and aftera training camp and after 2 weeks of recovery train-theoretical possibility we must return to the thresh-ing on performance, mood state and reaction time.old theory.[29] Satz[29] proposed that brain lesionsResults were compared with an age- and sex-and also other diseases can be detected when theymatched physically active control group. Five cy-are still asymptomatic using challenging assessmentclists performed worse and showed disturbed moodtechniques. Thus, if tasks of psychomotor speed arestates after the training camp but were fully recov-made challenging enough, even asymptomatic over-ered after recovery training. Reaction times of theseloads could be detected. Indeed, performance on acyclists with FO were longer than reaction times oftask of psychomotor speed seems to be reducedthe control group, although the differences were justunder demanding circumstances.not significant.[84]

Rietjens et al.[34] compared psychomotor speed These findings support the idea of Satz[29] thatbefore and after overload training. Seven well sub-threshold conditions can be detected using chal-trained cyclists increased their training volume by lenging assessment techniques. These findings also107% during 2 weeks together with an increase in give support to our hypothesis that demanding taskstraining intensity. The cyclists were assessed on, of psychomotor speed can be such assessment tech-among other measures, an incremental graded cy- niques. Additional support for our hypothesis is thecling test, a time trial and the finger pre-cueing task, finding that tasks of psychomotor speed can differ-a complex reaction time task. No significant differ- entiate between athletes with a positive stress regen-ences were found on maximal power output, maxi- eration balance and athletes with a negative stressmal heart rate or maximal lactate in the incremental regeneration balance.[85] Nederhof et al.[85] foundgraded cycling test. Time-trial performance was also that healthy, high-level rowers who experiencednot significantly different after compared with more stress performed worse on the Vienna determi-before the period of overload training. Still, a differ- nation test, whereas rowers who perceived lowerence was found in performance on the most difficult levels of regeneration performed worse on the fingerconditions of the finger pre-cueing task after the pre-cuing task.period of overload training compared with a controlgroup.[34] Thus, although these athletes did not expe-

8. Conclusionrience FO, NFO or OTS, as performance was notimpaired, they did show impairments in psychomo-tor speed after a period of overload training. Preliminary evidence for psychomotor speed as

an early marker for NFO and/or OTS is promising.However, it is necessary to conduct more studies toget insight in psychomotor speed over the full train-ing continuum and to get insight in differences be-tween tasks of psychomotor speed to be able todevelop a tool for the early detection of NFO and/orOTS.

Acknowledgements

Preparation of this manuscript was financially supportedby the Dutch Ministry of Health, Welfare and Sport. Theauthors have no conflicts of interest that are relevant to thecontent of this article.

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Fig. 2. Reaction times of healthy controls plotted against reactiontimes of patients with chronic fatigue syndrome (CFS).

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826 Nederhof et al.

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College of Sport Science, 2004: 288speed is a possible marker for overreaching. Abstract Book ofthe 10th Annual Congress of the ECSS; 2005 Jul 13-16;Belgrade. Belgrade, Serbia: European College of Sport Sci-ence, 2005: 101 Correspondence and offprints: Esther Nederhof, Center for

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E-mail: e.nederhof@rug.nlpress

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