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Table 2 Characteristics of the included studies examining the effect of aerobic exercise on pain sensitization

From: Does aerobic exercise effect pain sensitisation in individuals with musculoskeletal pain? A systematic review

Author (year), Country Demographics
n (% Female)
Mean(SD) age (years)
Study inclusions/exclusions of musculoskeletal (MSK) pain group Pain sensitization assessment Aerobic exercise protocol (including type and dosage) Results Conclusions
Experimental, repeated measures studies
Hoffman (2005), USA Chronic LBP subjects
n: 8 (50%)
Age: 40(10)
Healthy subjects
n: 10 (70%)
Age: 34(8)
Inclusions
-LBP≥1 year
-Clinical pain: stable and non-neurological
Exclusions
-Use of narcotics
-Inability to walk without a device
-Sacroiliac joint dysfunction
-Involvement in a regular exercise or treatment program
-Major surgery in the past year
-History of spondyloarthropathy
-Spinal infection, fracture, spondylolisthesis or malignancy
-Cardiac, pulmonary or metabolic disorders, or diseases involving sensory nerves
-Conditions preventing safe participation in exercise
-Pregnancy
Device: Pressure pain stimulator with Lucite edge (6mmx0.25mm)
Force: 9.8 N
Locations: dorsal surface of the middle phalanx of the non-dominant index finger
Duration: 2 min
Scale: 100mm VAS
-1st PPT 1 min before starting aerobic exercise
-Cycling on ergometer for 5 min at 50% VO2max followed by 20 min at 70% VO2max
-2nd PPT 2 min after completion of cycling
-3rd PPT 28 min after completion of the 2nd
PPT (32 min post exercise)
Mean (SD) pressure pain ratings were significantly lower at 2 min (57(26) mm) and 32 min post exercise (62(27) mm) compared to pre-exercise values (79(12) mm) (p<0.05). Exercise-induced analgesia to an experimentally induced pressure pain was evident for >30 min after aerobic exercise from cycling in people with chronic low back pain and minimal/ moderate disability.
Meeus (2010), Belgium Chronic LBP
n=21 (48%)
Age: 41.6(12.4)
Chronic fatigue syndrome with chronic pain
n=26 (19%)
Age: 41.5(11.4)
Healthy subjects
n=31 (32%)
Age: 40.0 (12.6)
Inclusions
-18-65 years
- Non-specific LBP≥3 months
- Sedentary
Exclusions
-Pregnancy and ≤1 year postnatal
-Neurological or cardiovascular problems
- Specific LBP pathology
-History of spinal fracture, spinal surgery, severe degenerative change, severe scoliosis, osteoporosis, obesity, radicular signs, malignancies and metabolic or rheumatological diseases
Device: Fisher algometer
Force: Increased at a range of 1 kg/s
Locations: skin web between thumb and index finger, 5 cm lateral to L3 spinous process, insertion of deltoid and at the proximal third of the calf
Measures: Mean of last 2 of 3 consecutive measurements at each site separated by 10 s before and after each exercise bout.
6 bouts of exercise on a bicycle ergometer
-Incremental, starting at 20 W and increasing in steps of 10 W/minute
-Each bout began with a warm-up period, starting from 0 and increasing by 1 W every 2 s
-Exercise consisted of 2 incremental 1-minute steps
-Each bout finished with a cool down of 30 s
-Subjects instructed to stop when tired or couldn’t pedal at frequency of ≥70 rpm
-6th exercise bout ended at 130 W
Baseline
There were no
significant differences in PPTs between healthy subjects
and patients with chronic LBP (p=NA).
Post-exercise
The mean(SD) PPTs increased following exercise in healthy and CLBP individuals:
Healthy: 7.11(2.74) to 7.56(3.17) (p=0.001).
CLBP: 8.10(3.02) to 8.28(3.49) (p=0.001).
After submaximal
aerobic exercise, mean pain thresholds
increased in patients with chronic LBP.
There was no evidence of hyperalgesia and abnormal
central pain processing during submaximal aerobic exercise in individuals with chronic LBP.
Vaegter (2016), Denmark Chronic musculoskeletal pain
n: 61(69%)
Age: 45.4(11.2)
Low (LPS; N=30) and high (HPS; N=31) pain-sensitivity groups were created on the basis of a median split of the average PPTs.
Inclusions
-Chronic musculoskeletal pain (37 low back, 16 neck, 7 shoulder, 1 elbow)
-Referral to multidisciplinary pain clinic
Exclusions
-Neurological, psychiatric or CVD conditions
Device: Manual handheld algometer
Force: Increment rate of 30 kPa/s over stimulation area 1cm2
Locations: Middle of both quadriceps femoris, dominant biceps brachii and non-dominant upper trapezius muscle
Measures: Before, after, and 15 min after the exercise
Aerobic stationary cycling
-Age-related target HR corresponding
to 50% VO2max and 75% VO2max
-Patients pedaled at ~70 revolutions per minute
-First 2 min: warm up (HR: 50% VO2max)
-Resistance increased over next 3 min until HR: 75% VO2max
-Continuation to maintain this HR for 10 min
Baseline
PPT and pain tolerance were decreased in the HPS group compared to the LPS
(P=0.001; 0.02 respectively).
Post-exercise
Widespread PPTs increased after exercise in both groups
HPS: 272.8(158.0) to 319.1 (162.1)
(p<0.05)
LPS: 574.7(362.1) to 646.3(378.8) (p<0.05)
Cuff PPT increased and pain tolerance limit decreased
after exercises in LPS only (p<0.001).
Temporal summation of pain was increased after bicycling in HPS (p<0.005).
Pain tolerance increased after exercise in both groups (p<0.001).
Hypoalgesia after the exercise was
impaired in patients with chronic pain and high pain sensitivity
compared with patients with less pain sensitivity.
Vaegter (2018), Denmark Chronic musculoskeletal pain
n: 54(72%)
Age: 45.7(11.2)
Participants were subgrouped into high and low kinesiophobia based on the recommended threshold for a high degree of kinesiophobia on the Tampa scale.
All patients recruited after referral to a multidisciplinary pain clinic Device: Manual handheld algometer
Force: Increment rate of 30 kPa/s over stimulation area 1cm2
Locations: Middle of both quadriceps femoris, dominant biceps brachii and non-dominant upper trapezius muscle
Measures: Before, after, and 15 min after the exercise, 2 assessments per site, average used for analysis
2 exercise conditions on 2 different days
-Cycling
-Isometric contraction
Aerobic stationary cycling
-Age-related target HR corresponding
to 50% VO2max and 75% VO2max were determined
-Patients pedaled at ~70 revolutions per minute
-First 2 min: warm up (HR: 50% VO2max)
-Resistance increased over next 3 min until HR: 75% VO2max
-Continuation to maintain this HR for 10 min
Baseline
The low kinesiophobia group had higher PPTs than the high kinesiophobia group, however no significant differences were found between the groups (p=0.09-0.59).
Post-exercise
No significant differences were found in percentage increase in PPTs between the high and low kinesiophobia groups post-exercise (p=0.12-0.58).
Although kinesiophobic beliefs influence pain intensity, they did not influence PPTs and EIH significantly, suggesting that exercise can induce hypoalgesia in subjects with chronic musculoskeletal pain, regardless of such belief.
Fingleton (2017), Ireland OA group
n:40
Divided into:
-Abnormal CPM (decrease or absence of change in PPTs) (n=19)
-Normal CPM (increase in PPTs) (n=21)
Control group
n:20 aged and sex matched subjects
Inclusions
-Knee OA based on ACR criteria and pain >3/10 on a numerical rating scale
-Main pain from knee OA
Exclusions
-Total knee replacement and if <90 degrees knee flexion
-Rheumatologic disease such as RA, fibromyalgia or ankylosing spondylitis
- Neurologic disorder such as Parkinsons disease, shingles, multiple sclerosis or stroke
- Cognitive impairment
- Current use of antidepressants or anticonvulsants
Device: Handheld pressure algometer
Force: 2cm2 probe, pressure applied at a rate of 30KPa/s
Locations: Medial joint line, quadriceps
femoris muscle and volar surface of the forearm
Measures: Average of 2 PPT measurements was recorded for
each site
Aerobic exercise protocol
-Cycle ergometer
-Submaximal exercise protocol used: Aerobic Power Index test
-Exercise duration varied between 4 and 10 min
-Pain was monitored on a numerical rating scale after each minute
-If pain at the knee joint exceeded 3/10, the participant’s workload
was reduced by 25 W by decreasing rate of pedaling and/or resistance
There were significant differences between abnormal
CPM, normal CPM and control groups for changes in
PPTs during
and post-aerobic exercise (F2,55=4.860, p=0.01)
The abnormal CPM group showed a decrease in PPTs (168.9(43.1) to 152.8(52.3)), while the normal CPM and
control groups showed an increase in PPTs (184.3(58.1) to 205.7(76.1) (P<0.05) and 218.0 (93.2) to 237.5 (111.7) p>0.05 pre and post exercise respectively).
Knee OA patients with abnormal CPM demonstrated
significantly increased pain sensitivity
in response to exercise,
while knee OA patients with normal CPM and controls demonstrated a significant decrease in their pain
sensitivity in response to exercise suggestive
of normal function of EIH.
Vaegter (2021), Denmark n: 96 (37.5%)
Age:
Mean (range): 47(20-73)
Inclusions
- Individuals ≥ 18 years who were adept in Danish
-Pain primarily in the lower back
(+/- pain radiating to the legs)
Exclusions
-Pregnancy, neurological, psychological or cardiovascular diseases, and current or previous alcohol or drug addiction
Device: Manual pressure algometry
Force: stimulation probe of 1 cm2 was used and the pressure was increased with 30 kPa/s
Locations: Left erector spinae and left calf muscles
Measures: average PPTs across two repetitions at each
site
6 min walk test on 20 m course between 2 cones No significant main effects were found for PPTs. However,
a significant interaction between time and Walk-Pain Index was found in the RM-ANOVA of the PPTs (F(1,94)=5.56, p=0.02, partial ƞ2 = 0.056).
Post hoc testing showed an increase in PPTs after walking in individuals who reported no or little increase in NRS scores of back pain
intensity, and a decrease in PPTs after walking in individuals who reported an increase of 2 or more in NRS back pain intensity scores.
This study found most individuals experienced exercise-induced hypoalgesia after walking, with the exception of those that reported an increase in pain during walking and subsequently no hypoalgesia afterwards.
Sitges (2021), Spain Aerobic exercise
n: 21 (57%)
Age: 42.5 (9.72)
Control
n:19 (58%)
Age: 40.71 (9.95)
Inclusions
-18–59 years
-NSCLBP >6 weeks or with at least 3 episodes of LBP (lasting >1 week) in the year prior to the study
Exclusions
-High functional impairment compromising such activities as walking, sitting, or getting up from a chair, pain at time of evaluation and/or intervention >5 (out of 10) on the VAS, history or presence of sciatic radiating pain, referred pain, or OA of lower extremities, spine surgery, spinal or pelvic fracture, hospitalization for serious trauma, injuries, or traffic accidents, and systematic diseases affecting the locomotor system.
Device: Digital algometer
Force: Maximum 5 kg/cm2, no further details given
Locations: Erector spinae and gluteus medius muscles, sacrum and forefinger
Measures: no details given.
Aerobic intervention consisted of walking on a treadmill for 20 min at low–moderate intensity (65.9%±7% of maximum heart rate and 3.02±1.04 using the Borg Scale of Perceived
Exertion)
No information provided on the control group.
Mixed-model ANOVA revealed significant main effects of time on subjective PPIRs
(F1, 77=13.142,
p=0.001, ηp2=0.146).
Bonferroni post hoc analyses showed: lower PPIRs (2.581±1.584 vs. 2.865±1.629, p=0.001) and lower PPTs (2.581
±1.584 vs. 2.0.865±1.629, p=0.001) after intervention than before.
Mixed-model ANOVA revealed significant main effects of time on the pressure pain–sensitivity index (F 1, 77=7.074,
p<0.001, Greenhouse-Geisser correct: ηp2=0.084). Bonferroni post hoc analyses showed a reduction in pain sensitivity after intervention (1.217±0.945 vs. 1.082±0.918, p=0.010).
This study showed reductions in pain sensitivity after an aerobic exercise intervention in patients with non-specific, chronic low back pain.
Randomised controlled trial
Öte Karaca (2017), Turkey Aerobic exercise:
n: 25 (64%)
Age: 43.7(10.8)
Control:
n: 25 (68%)
Age: 44.9(7.9)
Inclusions
-MSK pain > 3 months
-Recruited from Physical Medicine Rehabilitation Department outpatient clinic
Exclusions
-Uncontrolled hypertension or arrhythmias
-Inflammatory arthritis
-Fibromyalgia
-Taking analgesia
-Physical therapy
-Regular exercise in the last 6 months
Device: Mechanical pressure algometer
Force: 1cm2 diameter pressure surface, 1 kg/s increments
Locations: Midpoint of forehead, bilateral volar surface of forearm and thumb nails
Measures: 3 consecutive measurements at 30-60 s intervals and mean taken to be pressure threshold
Intervention
-Submaximal aerobic exercise program
-Treadmill walking
-30 min 5 days a week for 2 weeks
-70-85% maximum HR
-With conventional physical therapy
Control
-Conventional physical therapy
PPT sum increased significantly in the exercise group from 19.9(6.1) to 22.0(6.3) (p=0.02), but was unchanged in the control group (20.7(5.4) to 20.9(6.7) (p=0.9)).
There was a significant increase in exercise duration in the exercise group compared with the control group (p=0.0002).
Pain intensity in both groups decreased significantly after exercise (p<0.001).
Short-term aerobic exercise along with conventional physical therapy decreased pain sensitivity in individuals with musculoskeletal pain.
Nielsen (2009), Denmark Aerobic exercise:
n: 11 (100%)
Age: 49(7)
Control:
n: 5 (100%)
Age: 48(11)
Inclusions
-Female office workers with monotonous, repetitive tasks
-Chronic pain in the neck, doctor-verified tightness of the upper trapezius muscle (UTM) and tenderness on UTM palpation
-Specific criteria
1) Pain for > 30 days in past year in neck/shoulder region, but with no more than 3 regions with symptoms
2) At least ‘‘quite a lot’’: on an ordinal scale of ‘‘a little” to ‘‘very much’’
3) Frequent: at least once a week on an ordinal scale of ‘‘seldom” to “almost all the time’’
4) Intensity: ≥2 on a scale from 0 to 9
Exclusions
-Previous trauma, life-threatening diseases, whiplash injury, cardiovascular diseases, arthritis in the neck and shoulder
Device: Electronic pressure algometer
Force: Contact diameter 10mm, increments of 30 kPa/s
Locations: Descending part of the trapezius muscle and the middle of the non-painful TA muscle
Measures: Before and after intervention, 3 times with at least 1 min between the measurements
Intervention
-Leg bicycling on stationary Monark ergometer at 70% maximal oxygen uptake for 20 min 3 x pw for 10 weeks
-Initial load 50% based on HR and gradually increased to 70% during the 10 weeks
Control
-No physical training, general health advice
Case-control study: Baseline
PPTs were significantly lower in neck/shoulder pain group than the control group:
Trapezius
Neck pain: (280(82) kPa)
Control: (479(119) kPa) (p< 0.05).
Tibialis anterior (reference muscle): Neck pain: (302(110) kPa)
Control: (464 (134)) (p< 0.05)
Intervention study Post-exercise
PPTs in tibialis anterior were increased in the cycling group [from
311 (113) to 386 (107) kPa; p<0.01].
Physical exercise, in general, lowers pain perception, resulting in normalisation of PPT in pain-free muscles.
Kocur (2016), Poland Nordic walking
n: 22 (100%)
Age: 54.5(3.7)
Control
n: 22 (100%)
Age: 56.7(2.9)
Inclusions
-Females 50-60 years, sedentary work for ≥ 6 h per day for ≥10 years
-Moderate or mild pain (VAS <6) in cervical area
-Lack of additional physical activity in free time
Exclusions
-Locomotor system disorders preventing physical exercises
-Physical work, work in standing position, sedentary work for < 10 years
-Participation in physical activity over the past year
-Acute inflammatory conditions
-Acute pain in the cervical area and shoulders VAS >6
-Idiopathic pain
-Cardiovascular or pulomonary disorders or other internal diseases
Device: Electronic pressure algometer
Force: Not specified
Locations: Trapezius par desc, mid trapezius, latissimus dorsi, infraspinatus, pectoralis major, triceps brachii, brachio-radialis
Measures: Test performed twice 10 s apart, second result used for calculations
Intervention
-12 week Nordic walking training: 3 times a week of 1 h
-Outdoors with at least 2 instructors controlling the marching technique and regulating pace
-Preceded by 10 min warm-up and ended with 5-minute cool down
-Intensity between 40-70% of HRR
Control
-Told not to change their movement routines and habits for the period of 12 weeks
There was
significant improvements in PPTs for Nordic Walking:
Trapezius pars descendens (1.32(0.5) to 1.99(0.6) p=0.002), Middle trapezius (2.92(0.9) to 3.30(0.8) p=0.002), Infraspinatus (1.63(0.6) to 2.93(0.8) p=0.001)
Latissimus dorsi (1.66(0.6) to 2.21(0.5) p=0.02)
No statistically significant improvement in PPTs were observed in pectoralis major, triceps and brachioradialis in the
treatment group p=(0.12-0.39).
No improvement was recorded in any muscle groups in the control group (p=0.05-0.92).
Nordic Walking has a high potential of reducing sensitivity to pressure
(increased PPT) in the muscles of that region.
Bruehl (2020), United States Aerobic
n: 44 (55.3%)
Age: 40 (10)
Control
n: 49 (65.9%)
Age: 41.9 (9.45)
Inclusions
-18-55 years
-Daily low back pain of ≥3 months duration, with an average past month pain intensity (VAS) of ≥3/10
-Medical provider diagnosis consistent with CLBP
-No self-reported history of liver or kidney disorders, PTSD, BPD, psychotic disorder, diabetes, seizure disorder, alcohol or drug dependence, or daily use of opioid analgesics
-Engaged in moderate or vigorous exercise <2 days per week and <60 min per week
Exclusions
-Self-reporting CP related to malignancy or autoimmune disorders
-Pregnancy
Device: Computerised Medoc TSAII NeuroSensory Analyser
Force: 40 °C and increasing at a ramp rate of 0.5 °C per second until tolerance was reached
Locations: slightly different location of the ventral forearm for each stimulus to avoid local sensitization effects
Measures: 3 trials were conducted for heat pain tolerance (with the mean value used for
analyses)
Intervention
-Supervised, individual aerobic exercise training program 3 times per week for 6 weeks
-Exercise session included a 5-minute warm-up, 30 min of aerobic exercise and a 5-minute cool-down
-Treadmill walking/running,
stepping, elliptical, or cycling exercise as preferred by the participant
-Duration and intensity of exercise was progressively increased
-Participants began with 10-15 min of exercise at 40-55% HRR (RPE =11-12, light) during the first week, 20-30 min of exercise at 55-70% HRR (RPE = 12-13, somewhat hard) during the second week, then 30 min of exercise at 70-85% HRR (RPE=14-16, hard) for the remainder of the study
Control
-Asked to maintain their normal daily activity levels throughout the study
Baseline
Evoked thermal pain responses at baseline did not differ
significantly between groups.
Post-exercise
-Significant main effect of intervention
Group on MPQ-SF Total ratings [F(1,77) =5.80, P =0.018, h2 = 0.064]
-Participants in the exercise group
displayed slightly improved pain responsiveness (decreased
thermal pain ratings) after the 6-week intervention (M = 0.33, SE =0.70), whereas control group participants reported an increase in thermal pain responses over time (M=22.04, SE=
0.68)
-However, group-level mean reduction in evoked pain responsiveness
observed in the exercise condition was not significantly different from zero [t(37) 5 0.63, P = 0.54]
-Women in the exercise group exhibited significantly larger increases in EO function (M = 1.68, SE = 0.91) than women in the control group [M = -0.93, SE =0.80; F(1,46) = 5.35, P =0.025]. This intervention effect was not significant in men.
Supervised progressive aerobic exercise training can
significantly decrease pain in individuals with
CLBP, with evidence supporting enhanced pain inhibitory function.
  1. MSK -musculoskeletal, LBP -low back pain, VAS -visual analogue scale, VO2 -volume of oxygen consumed, PPT -pressure pain threshold, HPS -high pain sensitivity, LPS -low pain sensitivity, HR -heart rate, HRR -heart rate reserve, EIH -exercise-induced hypoalgesia, OA -osteoarthritis, CPM -conditioned pain modulation, ACR -American College of Rheumatology, UTM -upper trapezius muscle, kPa -kilopascals, NA – Not available. PTSD -posttraumatic stress disorder, BPD -bipolar disorder, NSCLBP – non-specific chronic low back pain, PPIRs - pain pressure intensity ratings, NRS -numerical rating scale, MPQ-SF -McGill Pain Questionnaire (short form), RPE -rating of perceived exertion, EO -endogenous opioids, CLBP -chronic low back pain