Table 1.

Included studies characteristics

Study	Study Design	Participants that completed the study (n, male/female)	Age (years, mean ± SD)	Details of Exercise	Type of exercise	Intensity of exercise	Outcomes for pain	Assessment timing	Conclusion	MINORS Score
Ohlman et al. 2018	Quasi-experiment	20/32	Male=67.6±5.3 Female=67.2±4.9	A submaximal isometric handgrip exercise at 25% of MVC by the left arm	Strength	Light	PPT 30-seconds of continuous heat pain test	Before and immediately after exercise	Older adults did not exhibit EIH after submaximal isometric exercise. However, those who did more MVPA per week experienced a greater magnitude of pain inhibition after acute exercise.	22
Persson et al. 2000	Quasi-experiment	0/25	Younger: 44±10.18	A weight belt of 1 kg was wrapped around the wrist of the subject’s hand. In the resting position, the subject held her forearms and hands on a pillow in her lap. During test contractions for EMG recording (each lasting 15 seconds) and during the endurance test, the subject’s right arm was abducted 90[degrees] in the scapular plane, with a slightly flexed (20[degrees]) elbow, pronated with the thumb pointing downward	Strength	Intense	PPT	Before and after the endurance test	The mechanisms of recovery from fatigue and nociception are independent of each other. The bilateral PPT increases might be explained by central antinociceptive mechanisms activated by static muscle work.	16
Koltyn K. F. et al. 1998	RCT	7/6	23±5	Exercise group:45 minutes of lifting three sets of 10 repetitions at 75% of the individual’s one repetition maximum. Control group: Quiet rest consisted of 45 minutes of sitting quietly in a room free from distractions.	Strength	Moderate	PPT Pain ratings	Before and after (5 and 15 mins) exercise and quiet rest	A single bout of resistance exercise is capable of modifying the sensation of experimentally induced pain.	20
Koltyn K. F. et al. 2001	Quasi-experiment	15/16	Male=22±5 Female=21.5±2	2 sessions: 1)Squeezed a hand dynamometer with their right hand (dominant hand) as hard as they could for 5 s, rested for 2 min, and then squeezed the hand dynamometer again for 5 s; 2) Submaximal isometric exercise consisted of squeezing the hand dynamometer with the right hand between 40% and 50% of maximum for 2 min.	Strength	Moderate and intense	PPT Pain ratings	Before and immediately after exercise	It is concluded that: 1) men and women differed in PT, SBP, and DBP before ISO EX; and 2) analgesia after ISO EX is observed more consistently in women.	17
Koltyn K. F. et al. 2007	Quasi-experiment	0/14	19.5±1	2 sets of submaximal (40% to 50% of max) isometric exercise consisting of squeezing a dynamometer for 2 minutes with the dominant hand.	Strength	Moderate	PPT Pain ratings	Before and immediately after exercise	Submaximal isometric exercise performed for 2 minutes resulted in ipsilateral and contralateral hypoalgesia responses.	17
Kruger S. 2016	RCT	Healthy control group=29 No other demographic characteristics data provided	Control group=48±13	Walk for a maximum of 30 min with a self-chosen velocity.	Aerobic	Moderate	PPT	Before and immediately after exercise	Subjects were able to perform an endurance exercise with self-chosen velocity for 30 min as recommended, without increasing the acute pain condition.	18
Focht B.C. et al. 2009	Quasi-experiment	21/0	21.4±2.5	2 RE sessions, each session consists of leg extension, torso-arm pull-down, chest press, and overhead press, 3 sets of 10 repetitions 75% of each individual’s 1-repetition maximum.1st session at 6:00–8:00am and repeat at 6:00–8:00 pm.	Strength	Moderate	PPT Pain ratings	Before and after (1 and 15 mins) each bout of RE.	Acute RE results in alterations in the perception of experimentally induced pressure pain and that this hypoalgesic response is not influenced by the time of day that RE is performed.	17
Bartholomew et al. 1996	Quasi-experiment	17/0	Younger (no more details)	20 min of self-selected exercise	Strength	Moderate	PPT Pain tolerance	Before and immediately after exercise	The analgesic effect of exercise is not limited to controlled experimental conditions but generalizes to naturally occurring stimulations.	11
Falla D. et al. 2014	RCT	Control group:9/8	Control group:29.4±7.4	Subjects were asked to repetitively move a box with hole-shaped handles, loaded with a weight of 5 kg.	Strength	Light	PPT	Before and immediately after exercise	LBP alters the normal adaptation of lumbar erector spinae muscle activity to exercise, which occurs in the presence of exercise-induced hyperalgesia. Reduced variability of muscle activity may have important implications for the provocation and recurrence of LBP due to repetitive tasks.	15
Kosek E. et al. 1995	Quasi-experiment	0/14	36.8±9.96	The maximum isometric knee extensor strength at a 90° of knee flexion was determined 3 times with I min of rest between trials. The best value was used for calculating 25% of MVC.	Strength	Moderate	PPT	Before, during rest, during contraction and following contraction.	The results suggest that input from cutaneous and deeper tissues interacts with nociceptive activity set up by the pressure stimulus. Determining the degree of sensory modulation in muscle and skin in different chronic pain syndromes could become a functional method of patient assessment important for differential diagnosis, treatment evaluation, and follow-up.	18
Arroyo-Morales M. et al. 2012	Quasi-experiment	25/25	22.4±3.42	A standardized light warm-up protocol, followed by three 30-s Wingate tests on an ergometer cycle separated by 3-min recovery periods.	Aerobic	Intense	PPT	Before and immediately after exercise	High-intensity interval exercise induces a worse psychoneuroimmunological state in males than in females.	13
Agnew J. W. et al. 2018	Quasi-experiment	25 miles group=5/1 50 miles group =9/13 100 miles group =9/8	25 miles group =37.2±12.9 50 miles group =42.1±6.9 100 miles group =41.8±7.8	Complete 25 miles, 50 miles or 100 miles marathon	Aerobic	Intense	PPT CPM	Before and immediately after completion of 25°miles, 50°miles and 100°miles.	An increased peripheral and/or central pain sensitization starting at 25° miles and continuing throughout an ultra-marathon competition run in these conditions.	21
Burrows N. J. et al. 2018	RCT	Old group=5/6 Young group=4/7	Old group=61.3±8.2 Young group=25±4.9	Three sets of 10 repetitions were performed at 60% of the individuals’ 1RM. One-minute rest was given between sets.	Strength	Intense	PPT Pressure pain tolerance	Before and immediately after exercise	An acute bout of upper or lower body exercise evoked a systemic decrease in pain sensitivity in healthy individuals irrespective of age. The decreased pain sensitivity following resistance exercise can be attributed to changes in pain thresholds, not pain tolerance.	22
Lee H. S. et al. 2014	RCT	Aerobic exercise group(AG)=5 Strengthening exercise group(SG)=5 Control group(CG)=5 No other demographic characteristics data provided	AG=25.2±0.8 SG=71.2±5.3 CG=24.3±0.5	AG=walked on a treadmill for 10 and 40 min at 6.5 km/h; SG= performed 10 and 40 min of circulate training exercises that included a bench press, lateral pulldown, biceps curl, triceps extension, and shoulder press based on the perceived exertion. CG= rested in a quiet room without exercising for 10 and 40 min.	Aerobic Strength	Light Light	PPT	Before and immediately after 10 and 40 min of exercise	40 min is a more appropriate exercise time, although the efficacy of controlling pain did not differ be-tween strengthening exercise and aerobic exercise.	20
Lemley K. J.et al. 2016	Quasi-experiment	33/31	Young women=20.6 ±1.5 Young men=21.7 ±3.7 Old women=71.3±7.6 Old men=71.3 ±5.1	Before and after maximal velocity concentric contractions of knee extensors or elbow flexors (separate days).	Strength	Intense	PPT	Before and immediately after exercise	Under controlled conditions where muscle fatigue is similar, sex differences in EIH occur in young and older adults that is site specific (upper extremity). Only women experience EIH following acute single limb high-velocity contractions.	11
Lofgren M. et al. 2018	RCT	Control group=4/16	Control group=60±6	A right-leg isometric knee extension contraction and to maintain it until they were unable to sustain 30% of their MVC.	Strength	Moderate	PPT EIH	Before and immediately after exercise	A generally increased pain sensitivity but normal function of EIH among persons with RA and offer one possible explanation for pain reduction observed in this group of patients following clinical exercise programs.	19
Micalos P. S. et al. 2016	Quasi-experiment	10/0	21.2±3.4	Aerobic cycling exercise performed at 70 and 30°% of VO2peak on two separate visitations in a counterbalanced order.	Aerobic	Light/Moderate	PPT	Before and 5 min after exercise	Aerobic activity attenuates pressure pain sensitivity locally at the exercise muscle site following cycling exercise at 70% of peak oxygen uptake, however, may facilitate pain sensitivity following exercise at 30% of VO2peak.	14
Meeus M. et al. 2010	RCT	Control group=10/21	Control group=39.88±12.63	A submaximal aerobic exercise protocol on a bicycle ergometer: each plateau phase at a certain workload lasted for 60 s. Each exercise bout consisted of 2 plateau phases at incremental workloads.	Aerobic	Moderate	PPT VAS	Before and immediately after exercise	Hyperalgesia and abnormal central pain processing during submaximal aerobic exercise in chronic fatigue syndrome, but not in chronic low back pain. Nitric oxide appeared to be unrelated to pain processing.	20
Lewis Z. et al. 2018	Quasi-experiment	24/9	22.75±3.98	Rowed two 20-min time trials under two counterbalanced conditions-paired and large group	Aerobic	Moderate	PPT	Before, immediately post, 5-min post, and 10-min post each session.	Pain threshold were affected by a wide variety of synchronous activities. There was a significantly higher pain threshold in the large group than in the paired condition after 10 min of exercise.	13
Lemley K. J. et al. 2014	Quasi-experiment	24 No other demographic characteristics data provided	72.2±6.2	Isometric contractions of the left elbow flexor muscles of the following doses: 1) three brief MVC; 2) 25% MVC held for 2 min; 3) 25% MVC held to task failure.	Strength	Moderate and intense	PPT	Before and immediately after exercise	Older adults experienced similar reductions in pain after several different intensities and durations of isometric contractions. Both older men and women experienced increases in pain threshold, but only older women experienced reductions in pain ratings.	16
Fingleton C. et al. 2017	RCT	Control group=11/9	Control group=62±7.9	Aerobic exercise in a sitting position on a cycle ergometer and doing the Aerobic Power Index test. Isometric exercise: extend knee as far as could be achieved without pain >3/10. And then hold an isometric knee extension contraction until exhaustion.	Aerobic and strength	Intense	PPT CPM EIH	Before and immediately after exercise	Dysfunctional EIH in response to aerobic and isometric exercise in knee OA patients with abnormal CPM, and normal function of EIH in knee OA patients with an efficient CPM response.	18
Alsouhibani et al. 2018	RCT	15/15	19.3±1.5	Isometric exercise group: a submaximal (30% MVIC) iso-metric contraction of the right knee extensor muscles that was held for three minutes while seated upright on the edge of a plinth table. Control group: quiet rest	Strength	Moderate	CPM PPT	Before, during, and after ice water immersions.	Isometric exercise decreased CPM in individuals who reported systemic EIH, suggesting activation of shared mechanisms between CPM and systemic EIH responses.	21
Harris S. et al. 2018	Quasi-experiment	19/16	23.6±6.6	5 min knee extension isometric contraction at 20–25% MVC	Strength	Moderate	PPT OffA	Before and immediately after exercise	Five minutes of 20–25% MVC lower limb isometric exercise provided non-pharmacological pain modulation in young, active adults.	16
Gajsar H. et al. 2016	Quasi-experiment	12/17	29.97±6.06	120 seconds of the isometric Biering-Soerensen back extension test	Strength	Moderate	PPT	Before and immediately after exercise	Isometric back exercise produces local and remote hypoalgesia.	15
Naugle K. M. et al. 2014	Quasi-experiment	12/15	21.78±4.14	Vigorous aerobic exercise: 5-minute warm-up period and then cycled for 20 minutes at an intensity of 70% HRR. Moderate intensity aerobic exercise: 5-minute warm-up period and then cycled for 20 minutes at an intensity of 50–55% HRR.	Aerobic	Moderate and intense	PPT Suprathreshold pressure pain test. Static continuous heat test. Repetitive pulse heat pain test	Before and immediately after exercise	MAE is capable of producing a hypoalgesic effect using continuous and repetitive pulse heat stimuli. However, a dose-response effect was evident as VAE produced larger effects than MAE.	23
Naugle K. M. et al. 2014	Quasi-experiment	12/15	Younger (no more details)	A 3-minute trial of submaximal isometric handgrip exercise at 25% of MVC.	Strength	Moderate	PPT Suprathreshold pressure pain test. Static prolonged heat test. Temporal summation of heat pain	Before and immediately after exercise	The hypoalgesic response to submaximal isometric exercise is partially a function of sex and experimental pain test.	23
Naugle. K. M. et al. 2016	Quasi-experiment	Young adults=11/14 Old adults=9/9	Young adults: 21.7±4.1 Old adults: 63.7±6.6	Vigorous aerobic exercise: 5-minute warm-up period and then cycled for 20 minutes at an intensity of 70% HRR. Moderate intensity aerobic exercise: 5-minute warm-up period and then cycled for 20 minutes at an intensity of 50–55% HRR. Submaximal isometric exercise: the dominant arm contract at 25% of their MVC.	Strength Strength Aerobic Aerobic	Light Moderate Moderate Moderate	PPT Pain rating Temporal summation of heat pain	Before and immediately after exercise	Age differences in EIH following isometric and aerobic exercise, with younger adults experiencing greater EIH compared to older adults.	23
Gomolka S. et al. 2019	Quasi-experiment	15/15	24.4±1.8	15 minutes of heart rate–controlled aerobic cycling in two sessions.	Aerobic	Moderate	PPT	Before, immediately after, and 15 min after exercise.	Fair test–retest reliability of EIH after aerobic cycling for local and semi local body parts, but only in men.	16
Slater et al. 2009	RCT	6/7	27.1±1.4	Eccentric-only exercise: 5 sets of 20 arm contractions at 30% maximal wrist extension force for 4 weeks. Concentric–eccentric exercise: 5 sets of 10 eccentric/10 concentric contractions at 30% maximal wrist extension force for 4 weeks.	Strength	Intense	PPT	Before and immediately after exercise at each session	Mechanical hypoalgesia is induced by repeated low load exercises regardless of exercise mode, and this may prove beneficial if replicated clinically.	21
Vaegter et al. 2015	Quasi-experiment	28/28	23.5±2.19	2 min warm-up and then 3 min to achieve the ATHR and then continued bicycling for additional 10 minutes.	Aerobic	Moderate	PPT	Before, immediately after, and 15 min after conditioning and exercise	Cold pressor stimulation and aerobic exercise caused comparable multisegmental increases in PPT in active and inactive men and women.	20
Vaegter et al. 2016	Quasi-experiment	20/0	24.4±2.0	Session 1: 15 min quiet rest Session 2 and 3: 12 min rest and then 3 min submaximal isometric knee extension at 30% of MVC with the dominant leg.	Strength	Moderate	PPT PTT HPT	Before and immediately after exercise and rest	Hypoalgesia after submaximal isometric exercise is primarily affecting tolerance of pressure pain compared with the pain threshold.	21
Treseler et al. 2016	Quasi-experiment	0/19	20±1	Two 5-km performance time trials with CS or regular socks in a counterbalanced order separated by 1 week.	Aerobic	Moderate	PPT Muscle soreness	Before and immediately after exercise at each session	There were no significant improvements in average 5-km running time, heart rate, or perceived calf MS.	20
Staud et al. 2010	RCT	Control group=0/36	Control group: 44.7±11.0	Rotate the 1 kp flywheel consistently at 60 rpm until exhaustion, repeat twice alternating with 15-minute rest periods.	Aerobic	Moderate	VAS PPT	Before and after each rest-and-exercise period	Alternating strenuous exercise with brief rest periods not only decreased overall clinical pain of FM subjects but also their mechanical hyperalgesia.	20
Vaegter et al. 2018	RCT	21/13	25.8±3.4	2 sessions, each session consist of 15 min rest and 15 min bicycling	Strength	Moderate	PPT	Before and immediately after exercise and rest	Incremental bicycling exercise in-creased PPTs with fair relative and absolute reliability of the EIH response.	19
Van Weerdenburg et al. 2017	RCT	9/6	25±6.5	3 interventions consisting of 20 min of aerobic cycling, 12 minutes of isometric knee extension and a deep breathing procedure	Aerobic and strength	Moderate	PPT. Cold pressor test	Before and after each intervention	No hypoalgesic effect of aerobic and isometric exercise was found.	20

PPT: pressure pain threshold; CPM: Conditioned Pain Modulation; EIH: Exercise-induced analgesia; CPP: cold pressor pain; VAS: Visual Analogue Scale; MVC: maximum voluntary contraction; PTT: pain tolerance; HPT: Heat pain threshold; HRR: heart rate reserve; RM: repetition maximum; CS: compression stockings; OffA: offset analgesia; MVIC: maximal voluntary isometric contractions; ATHR: age-related target heart rate; PwH: patients with hemophilia; LBP: low back pain; SBP: Systolic blood pressure ; DBP: diastolic blood pressure; ISO EX: isometric handgrip exercise; RA: Rheumatoid arthritis.