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2011 39: 569Journal of International Medical ResearchHadjipavlou and PG Katonis

AT Dimitriadis, PJ Papagelopoulos, FW Smith, AF Mavrogenis, MH Pope, AH Karantanas, AGIntervertebral Disc Changes after 1 h of Running: A Study on Athletes

  

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The Journal of International Medical Research2011; 39: 569 – 579

569

Intervertebral Disc Changes after 1 h ofRunning: a Study on Athletes

AT DIMITRIADIS1, PJ PAPAGELOPOULOS2, FW SMITH3, AF MAVROGENIS2, MH POPE3,AH KARANTANAS4, AG HADJIPAVLOU1 AND PG KATONIS1

1Department of Orthopaedics and Traumatology, and 4Department of Radiology, PAGNIUniversity Hospital, University of Crete, Heraklion, Crete, Greece; 2First Department of

Orthopaedics, Attikon University Hospital, University of Athens, Athens, Greece;3Department of Radiology, Woodend Hospital, University of Aberdeen, Aberdeen, UK

The lumbar spines of 25 long-distancerunners were examined using an uprightmagnetic resonance imaging scanner. Allvolunteer runners were scanned beforeand after running for 1 h. Scanning wasperformed with the runners seated upright(neutral), leaning forwards (flexion) andleaning backwards (extension). Allmeasured discs showed a reduction in discheight after 1 h of running. A significant

reduction in disc height was observed inall three body positions (neutral, flexionand extension) after 1 h of running. Theresults showed that, in flexion, extensionand neutral positions, intervertebral discsundergo significant strain after 1 h ofrunning. The lowest disc-height reductionwas found at the L5 – S1 space in theneutral position; the same space had thehighest percentage of disc degeneration.

KEY WORDS: DISC DEGENERATION; LONG-DISTANCE RUNNERS; LUMBAR SPINE; INTERVERTEBRAL DISCS;UPRIGHT MAGNETIC RESONANCE IMAGING

IntroductionIn 1990 Swärd et al.1 observed largedifferences between the spines of eliteathletes and non-athletes. Disc degenerationwas 75% more prevalent in athletes than innon-athletes (31%).1,2 This observationsuggests that large changes occur in theintervertebral space as a result of the strainplaced on the spine during exercise.3 – 10 Suchchanges are more common in athletesduring periods of increased physical trainingor competition.11 – 13 Other investigators havetried to measure these increased loads on thelumbar spine using different methods.14 – 18

Magnetic resonance imaging (MRI) is asensitive, accurate and non-invasive methodfor observing and measuring changes in

intervertebral discs.19 – 22 With the advent ofupright, positional MRI, there came theopportunity to observe changes in theintervertebral space in different bodypositions and to observe whether theserelated to changes in disc position or discheight.

Using an upright MRI scanner, the aim ofthe present study was to investigate changesin disc height, degeneration and intensityafter a 1-h run by trained, long-distancerunners. The spine was imaged in differentbody positions, with runners sitting upright(neutral), leaning forwards (flexion) andleaning backwards (extension).Relationships between these changes andbody weight, age, sex and the existence (or

570

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

absence) of prior low-back pain were alsoinvestigated.

Subjects and methods SUBJECTSAll participants included in the study werevolunteers, with previous experience oflong-distance running, who wereaccustomed to constant running forapproximately 1 h (over a distance of 10km) on a regular basis. Participants wererecruited from the local population ofAberdeen, UK, between October 2003 andApril 2006, through advertisements in thelocal press. Study inclusion criteria were:being able to run continuously for at least 1h; and previous long-distance runningexperience. Exclusion criteria were:cardiovascular, metabolic or collagenicdiseases; high blood pressure; drug intake toimprove athletic performance; andnonsteroidal anti-inflammatory drug use 1week before the trial.

All volunteers were informed about thestudy and gave their written consent forparticipation. The study protocol wasapproved by the Ethics Review Committee ofthe University of Aberdeen.

MRI PROTOCOLImages of the lower back were taken usingthe Fonar Upright® Multi-Position™ MRIscanner (Fonar Corporation, Melville, NY,USA) at Woodend Hospital, Aberdeen, UK. Ineach subject, nine sagittal T2-weightedimages of the lumbar spine were obtained,together with three transverse T2 slices ateach of the five intervertebral disc levels.This protocol was repeated with runnersseated in neutral, flexion and extensionpositions. T2-weighted central sagittalimages were used for analysis in these threepositions before and after 1 h of running,together with the central transverse section

through each of the five lumbarintervertebral discs.

Before and after 1 h of running, eachlumbar disc was examined in all threepositions for height and degree ofdegeneration/dehydration (represented bychanges in signal intensity). Discdegeneration was graded, using the criteriaof DeCandido et al.23 on a scale of 1 (mildlydegenerated) to 3 (severely degenerated),based on the signal intensity of the discs onthe T2-weighted images. Disc height wasmeasured using the Dabbs and Dabbsmethod,24 which is the sum of the anteriorand posterior disc heights divided by two.Additionally, the difference in disc heightafter the 1-h run was compared with thediscs immediately above and below. Anychange in disc height before and afterrunning was correlated with signs of discdegeneration.

All runners completed a questionnaireregarding somatometric characteristics, suchas body weight, height, age, sex andprevious low-back pain (including anytreatment received for this pain). Bodyheight was measured before and after the 1-h run using a stadiometer.25 All subjectswere weighed by electronic precision scales.

For further analysis, the runners weresubdivided into five subgroups for each ofthe parameters of age, weight and height,and into two subgroups each according togender and the pre-existence or absence oflow-back pain. In each case, the behaviourof the discs after running was studied inrelation to the groups to which each runnerbelonged.

STATISTICAL ANALYSESStatistical analyses were carried out usingthe SPSS® statistical package, version 10.0(SPSS Inc., Chicago, IL, USA) for Windows®.The χ2 statistic (Pearson’s χ2 or Fisher’s exact

571

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

tests) was used for statistical analysis of theresults. A P-value < 0.05 was considered to bestatistically significant.

Results SUBJECTSIn total, 25 volunteer long-distance runnerswere included in the study ranging in agefrom 23 to 69 years. Fifteen were male and10 were female. The runners’ pre-runningbody weights ranged from 51 to 100 kg andbody heights ranged from 158 to 191 cm.Seventeen runners had a previous history oflow-back pain.

CHANGES IN BODY HEIGHTThere were varying degrees of reduction inbody height following the 1-h period ofrunning. One runner lost 2 cm of bodyheight after running, six had a 1-cmreduction and three had a reduction of 0.5cm. The remaining 15 runners showed noreduction in body height.

DISC HEIGHT REDUCTION ANDDEGENERATION/DEHYDRATIONFor all measured discs, a reduction in heightwas observed after 1 h of running. Themeasurements showed a statisticallysignificant reduction in the whole lumbarspine (P = 0.001) as well as in specific bodypositions (flexion P = 0.001, extension P =0.001 and neutral P = 0.001). After runningfor 1 h, the mean reduction of disc heightwas 4.88 ± 6.5 mm in neutral (P = 0.001,versus before running), 5.44 ± 5.1 mm inflexion (P = 0.001 versus before running)and 5.20 ± 5.9 mm in extension (P = 0.001versus before running). The mean reductionin all three positions after running for 1 hwas 5.17 ± 5.8 mm (P = 0.001 versus beforerunning).

In total, 23 of 25 runners had discs withdegeneration (92%): 57 discs out of the 125

examined presented with degeneration(45.6%). The highest percentage of discdegeneration was at the L5 – S1 level,where 20 of 25 discs (80%) were affected(Table 1). The lowest disc height reductionand the lowest overall mean reduction inall three MRI positions after 1 h runningwas also found at the L5 – S1 level. Thesecond lowest disc height reduction was atthe L1 – L2 space, the third lowest at the L4– L5 space, the fourth lowest at the L2 – L3space and the fifth lowest at the L3 – L4space (Table 1).

Runners in the youngest age group (20 –30 years old) represented 16% of all runners(Table 2); two of the four runners in this agegroup had a history of low-back pain. Discdegeneration was 40% in this group;however, they developed the highest discheight reduction of all the age groups (mean± SD 6.43 ± 2.5 mm in flexion). The secondyoungest age group (31 – 40 years)developed the second highest disc heightreduction (mean ± SD 5.89 ± 2.1 mm inflexion). More homogeneity was observed interms of disc behaviour in the second-youngest age group than in the youngest agegroup. In the second-youngest age group,relatively high disc height reduction (mean ±SD 5.83 ± 1.4 mm) also occurred in theneutral position whereas, in the youngestage group, high disc height reduction onlyoccurred in flexion. In the next two highestage groups, the greater the age (up to 60years), the less disc height reduction wasobserved in the flexion and neutralpositions. The 51 – 60 years age groupdeveloped relatively high mean disc heightreduction in extension (mean ± SD 5.82 ± 1.4mm).

Runners in the lowest body weight group(50 – 60 kg; n = 5) developed the highest discheight reduction in flexion (mean ± SD 7.02± 2.0 mm; no statistically significant

572

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

reduction versus the 71 – 80 kg weight group)(Table 3). They had the lowest mean discheight reduction in neutral (mean ± SD 3.84± 1.1 mm; P = 0.021 versus the 71 – 80 kgweight group) and the second-lowestreduction in extension (mean ± SD 4.45 ± 1.4mm; P = 0.021 versus the 91 – 100 kg weightgroup). Disc degeneration for the 50 – 60 kggroup was 48%. The second-lowest weightgroup (61 – 70 kg) was the largest,comprising 13 runners (52% of the studycohort). This group presented homogeneityof disc height reduction in all the threepositions after running (Table 3).

Runners in the shortest body height group(150 – 160 cm) represented 8% of the studypopulation (Table 4). This group had thelowest rates of disc height reduction in allthree body positions after running (mean ±SD neutral 3.55 ± 1.8 mm, flexion 4.40 ± 2.9mm, extension 2.92 ± 3.5 mm). In addition,this group had the lowest initial mean discheight before running (neutral 10.00 mm,flexion 10.00 mm, extension 9.25 mm). Thegreatest disc height reduction (mean ± SD6.49 ± 3.2 mm) was found in the flexionposition in the second-shortest height group(161 – 170 cm) after running.

In male runners (60% of the study cohort)

pre-existing low-back pain was present in73.3%; 40% of male runners showed bodyheight reductions after running (Table 5). Upto 44% of the male runners’ discs haddegeneration. The greatest disc heightreduction in males was found in extension(mean ± SD 5.62 ± 1.7 mm; P = 0.028compared with females) and the lowest inthe neutral position (mean ± SD 4.96 ± 1.8mm). Of the 10 female runners studied (40%of the study cohort), 60% reported pre-existing low-back pain and 40% showed areduction in body height. The greatest discheight reduction in the female group wasfound in the flexion position (mean ± SD5.93 ± 2.5 mm) and the lowest in extension(mean ± SD 4.37 ± 1.2 mm) (Table 5). Therewas a statistically significant difference inlow-back pain between males and females (P = 0.019); six females compared with 11males out of the 17 (68%) runners with low-back pain history. These runners hadreceived conservative treatment for theirlow-back pain.

Of the 17 runners with pre-existing low-back pain, 58.8% developed a reduction intotal body height and disc degeneration withloss of disc height was as high as 48% (Table6). This group developed the highest disc

TABLE 1: Relationship between disc degeneration and mean reduction in disc height in threemagnetic resonance imaging scans (neutral, flexion and extension positions) for allintervertebral discs of the lumbar spine after 1 h of running in 25 regular long-distancerunners

Mean reduction in disc height (mm)

Neutral Flexion Extension Discs with Disc position position position Overall degeneration, n (%)

L1 – L2 1.05 0.90 1.03 1.00 9 (36)L2 – L3 1.10 1.07 1.04 1.07 5 (20)L3 – L4 1.06 1.37 0.98 1.14 8 (32)L4 – L5 1.01 0.98 1.11 1.02 15 (60)L5 – S1 0.66 1.12 1.04 0.94 20 (80)Statistical significance P = 0.001 P = 0.001 P = 0.001 P = 0.001 P = 0.001

573

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

TABLE 2:

Relationship between age and body height reduction, disc height reduction and percentage of discs with degeneration after

1 h of running in 25 regular long-distance runners

Low-back pain

No low-back

Body height

Disc height, mean

Discs with

Age, years

Runners, n

(%)

history,

npain history,

nreduction,

nPosition

reduction, mm

degeneration, n

(%)

20 –

30

4 (1

6)2

20

Neu

tral

4.97

8 (4

0)Fl

exio

n6.

43Ex

tens

ion

4.27

31 –

40

6 (2

4)3

33

Neu

tral

5.83

6

(20)

Flex

ion

5.89

Exte

nsio

n4.

0641

– 5

08

(32)

62

4N

eutr

al5.

0119

(48

)Fl

exio

n5.

55Ex

tens

ion

5.36

51 –

60

5 (2

0)4

11

Neu

tral

3.88

17 (

68)

Flex

ion

5.14

Exte

nsio

n5.

8261

– 7

02

(8)

20

2N

eutr

al4.

177

(70)

Flex

ion

3.91

Exte

nsio

n4.

92To

tal

25 (

100)

178

10

574

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

TABLE 3:

Relationship between body weight and body height reduction, disc height reduction and percentage of discs with

degeneration after 1 h of running in 25 regular long-distance runners

Body weight,

Low-back pain

No low-back

Body height

Disc height, mean

Discs with

kgRunners, n

(%)

history,

npain history,

nreduction,

nPosition

reduction, mm

degeneration, n

(%)

50 –

60

5 (2

0)5

03

Neu

tral

3.84

a12

(48

)Fl

exio

n7.

02Ex

tens

ion

4.45

b

61 –

70

13 (

52)

76

4N

eutr

al4.

7131

(48

)Fl

exio

n4.

91Ex

tens

ion

5.12

71 –

80

4 (1

6)2

22

Neu

tral

6.01

6 (3

0)Fl

exio

n4.

81Ex

tens

ion

4.95

81 –

90

1 (4

)1

00

Neu

tral

4.70

3 (6

0)Fl

exio

n6.

45Ex

tens

ion

3.50

91 –

100

2 (8

)2

01

Neu

tral

5.92

5 (5

0)Fl

exio

n6.

17Ex

tens

ion

7.92

a P=

0.02

1 ve

rsus

the

71

–80

kg

grou

p.

b P=

0.02

1 ve

rsus

the

91

–10

0 kg

gro

up.

575

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

TABLE 4:

Relationship between body height and body height reduction, disc height reduction and percentage of discs with degeneration

after 1 h of running in 25 regular long-distance runners

Body height,

Low-back pain

No low-back

Body height

Disc height, mean

Discs with

cmRunners, n

(%)

history,

npain history,

nreduction,

nPosition

reduction, mm

degeneration, n

(%)

150

– 16

02

(8)

20

1N

eutr

al3.

556

(60)

Flex

ion

4.40

Exte

nsio

n2.

9316

1 –

170

10 (

40)

82

6N

eutr

al4.

4725

(50

)Fl

exio

n6.

49Ex

tens

ion

5.10

171

– 18

09

(36)

45

1N

eutr

al5.

0420

(44

)Fl

exio

n4.

45Ex

tens

ion

5.66

181

– 19

03

(12)

21

1N

eutr

al6.

383

(20)

Flex

ion

5.61

Exte

nsio

n5.

5819

1 –

200

1 (4

)1

00

Neu

tral

4.70

3 (6

0)Fl

exio

n6.

45Ex

tens

ion

3.50

TABLE 5:

Relationship between gender and body height reduction, disc height reduction and percentage of discs with degeneration

after 1 h of running in 25 regular long-distance runners

Low-back pain

No low-back

Body height

Disc height, mean

Discs with

Gender

Runners, n

(%)

history,

npain history,

nreduction,

nPosition

reduction, mm

degeneration, n

(%)

Mal

es15

(60

)11

46

Neu

tral

4.96

33 (

44)

Flex

ion

5.18

Exte

nsio

n5.

62a

Fem

ales

10 (

40)

64

4N

eutr

al4.

6624

(48

)Fl

exio

n5.

93Ex

tens

ion

4.37

a P=

0.02

8 ve

rsus

fem

ales

.

576

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

height reduction after strain in the flexionposition and the lowest in the neutralposition. The group of eight runners (32%)who reported no pre-existing low-back painshowed no loss of body height after exercisebut some disc degeneration (40%). All theaffected runners in this group had the greatestdisc height reduction in the neutral positionand the lowest reduction in extension. Therewas a statistically significant reduction inbody height after running in those with,compared with those without, a history oflow-back pain (P = 0.006).

DiscussionPrevious studies have shown a largedifference between the spines of eliteathletes and non-athletes, with discdegeneration levels of 75% in athletes versus31% in non-athletes.1,2 This was believed tobe the result of the increased loads on thespine to which the elite athletes weresubjected. Swärd et al.1,2 also found a closerelationship between back pain and reduceddisc height, and also between back pain andthe presence of degenerative discs, in a staticmodel without previous spinal strain. Othershave examined the effects of increased loadson the lumbar spine using differentmethods.14 – 18,22,26 Kimura et al.15 found areduction in disc height only at the L4 – L5intervertebral disc. In 1999, Inoue et al.27

noted a relationship between disc heightreduction in the L5 – S1 intervertebral discand degeneration in the disc above. In2001, in an MRI study, a relationshipbetween the signal intensity of theintervertebral disc and age (high signalintensity and small disc height in youngstudents; low signal intensity and big discheight in middle-aged volunteers) wasobserved.21 Thus, although Swärd et al.1

had previously indicated a relationshipbetween pain, small disc height and

TABLE 6:

Relationship between pre-existing low-back pain and body height reduction, disc height reduction and percentage of discs with

degeneration after 1 h of running in 25 regular long-distance runners

Pre-existing

Runners,

Body height

Disc height, mean

Discs with

low-back pain

n (%

)Males,

nFemales,

nreduction,

nPosition

reduction, mm

degeneration, n

(%)

Yes

17 (

68)

116

10N

eutr

al4.

7941

(48

)Fl

exio

n5.

85Ex

tens

ion

5.37

No

8 (3

2)4

40

Neu

tral

4.95

16 (

40)

Flex

ion

4.69

Exte

nsio

n4.

58To

tal

25 (

100)

1510

577

AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running

degeneration in athletes, Luoma et al.21

indicated there was a relationship betweenage, disc height and degeneration in non-athletes.

In 2000, a pilot study with elite athletesshowed an increased relationship betweenlow-back pain and reduction in MRI signalintensity with reduction of disc height(comparing the affected disc with those justbelow and above it).13 This study alsoreported that the disc space with the highestreduction in height and the largestpercentage of degeneration was at the L5 –S1 level.13

According to Boos et al.,19 MRI is asensitive, accurate and non-invasive methodfor representing changes in intervertebraldiscs. The ability to conduct MRI scans in theupright position after 1 h of runningprovides the opportunity to observe changesin the intervertebral disc space in the normal(seated) neutral position and during changesin body position. Upright MRI scanning alsoenables evaluation of whether changes inbody height after exercise are related tochanges in disc position or disc height in realtime after increased spinal loading. Asshown in the present study, a statisticallysignificant reduction in disc height wasobserved in the three body positionsexamined (neutral, flexion and extension)after 1 h of running. This indicated thatrunning placed a significant strain on thediscs in these body positions. According tothe statistical analysis in the present study,no position was superior to another as far asdisc height reduction was concerned.

Although athletes did not undergofurther MRI scans in the present study,according to the literature, disc heightrecovery to its previous height isexpected.14,28 – 32 The lowest disc heightreduction after running was found at the L5– S1 space (0.66 mm mean loss in neutral

position). This space also had the highestpercentage of discs with degeneration (80%)and the average disc height reduction afterrunning for all three positions was 0.94 mm.The second-lowest disc height reduction wasfound at the L1 – L2 space, followed in turnby the L4 – L5, L2 – L3 and L3 – L4 spaces.Intervertebral disc height reduction in thethree body positions was present in runnersof all ages, but was unrelated to the runners’ages. Interestingly, in terms of the influenceof body weight, a lower body weightpositively affected discs in the extension andneutral positions.

Body height affected disc height reductionafter exercise in all three body positions; thiswas obvious from the changes in disc heightseen in the runners. The greater the initialdisc height, the greater the height reductionafter running, although this difference wasnot statistically significant.

Discs appeared to behave differently inthe various body positions in both sexes.Females showed greatest flexibility in theflexion position and lowest flexibility inextension; males showed greatest flexibilityin extension and lowest flexibility in neutral.In extension, there was a statisticallysignificant difference between the sexes. Ahigher percentage of males developed low-back pain and males showed a lowerpercentage of disc degeneration, but nostatistically significant relationship betweenthese two parameters and disc heightreduction after running was observed.

The present study demonstrated asignificant reduction in disc height that wasnot dependent on the presence of low-backpain, as measured by MRI in the seatedposition, after 1 h of continuous running.

Conflicts of interestThe authors had no conflicts of interest todeclare in relation to this article.

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• Received for publication 19 November 2010 • Accepted subject to revision 9 December 2010• Revised accepted 16 March 2011

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Author’s address for correspondenceDr Anastasios T Dimitriadis

Faculty of Medicine, University of Crete, PO Box 1352, 71110 Heraklion, Crete, Greece.E-mail: anastasiosdimitriadis@msn.com

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AT Dimitriadis, PJ Papagelopoulos, FW Smith et al.Intervertebral disc changes after 1 h of running