Mechanisms of Isometric Exercise-Induced Hypoalgesia in Young and Older Adults

Pain reduction following exercise (exercise-induced hypoalgesia; EIH) is well-established in young adults. Specific to isometric exercise, the greatest EIH follows low intensity contractions held for long duration. The EIH response of older adults is not known; and the mechanisms for EIH are unclear at any age. This dissertation aimed to address these unknowns through a series of three studies. In study one, repeatability of pressure pain reports (pain threshold and pain ratings) was assessed in healthy older adults, including the impact of psychological factors. Pain reports, measured before and after quiet rest, did not change following quiet rest. Higher state anxiety was associated with greater pain. Study two examined the impact of isometric contractions that varied in intensity and duration on pain relief in healthy older adults. Pressure pain was assessed before and after isometric contractions of the left elbow flexor muscles. Unlike young adults, older adults experienced EIH similarly across different isometric exercise tasks and women experienced greater pain reduction than men. Anxiety did not influence EIH. Conditioned pain modulation (CPM; a reduction in pain to a test stimulus in the presence of a noxious conditioning stimulus) has been hypothesized to augment EIH when exercise is painful. In study three, CPM and EIH were assessed in healthy young and older adults. CPM was measured as the difference in pressure pain with the foot immersed in neutral-temperature water versus noxious ice water. While young adults experienced CPM, older adults experienced a range of responses from hypoalgesia to hyperalgesia with foot immersion in the ice water bath. CPM predicted EIH and was associated with state anxiety; however state anxiety was unrelated to EIH. Results for age and sex-related differences in pain perception varied across studies or sessions. The results of this dissertation suggest anxiety influences pain sensitivity, but not magnitude of EIH. Older adults, particularly women, experience reductions in pain following isometric exercise and are less dependent upon task than young adults. CPM may predict EIH response following isometric exercise in both young and older adults and may be a useful tool in clinical decision making for adults experiencing pai

Conditioned Pain Modulation Predicts Exercise-Induced Hypoalgesia in Healthy Adults

Introduction: Conditioned pain modulation (CPM) is the concept that pain inhibits pain and has potential rehabilitation implications for exercise prescription. The purpose of this study was to determine whether changes in pressure pain perception after a thermal conditioning stimulus (i.e., CPM) was attenuated with aging and whether CPM predicted pain relief after exercise (exercise-induced hypoalgesia (EIH)) in healthy young and older adults. Methods: Twenty young (21.9 ± 3.3 yr, 10 men) and 19 older (72.0 ± 4.5 yr, 10 men) adults participated in three sessions: one familiarization and two experimental (EIH and CPM) sessions. Pressure pain perception was assessed using a weighted Lucite edge placed on the right index finger for 1 min. EIH was determined by measuring pressure pain perception before and after prolonged submaximal isometric contraction of the elbow flexors. CPM was assessed by measuring pressure pain perception at the finger while the foot was immersed in neutral water versus painful ice water. Results: Young, but not older, adults reported a decrease in pressure pain at the finger while their foot was immersed in the ice water bath compared with the neutral bath (i.e., CPM, trial–age: P = 0.001). Pressure pain ratings decreased after exercise (P = 0.03) that was perceived as painful (peak arm pain, 7.0 ± 3.3) for both young and older adults. Regression analysis showed that after controlling for age and baseline pain, CPM predicted EIH (model adjusted R2 = 0.23, P = 0.007). Conclusions: CPM was attenuated in older adults, as measured with a noxious pressure stimulus after a thermal conditioning stimulus, and adults with greater CPM were more likely to report greater EIH

Is Compressed and Limited Synchronous Delivery of Anatomy Content in a Hybrid Delivery Format Effective in Transitional OT Student Learning?

Hybrid occupational therapy (OT) students transitioning from certified OT assistants (COTAs) to OTs can successfully learn graduate-level anatomy in a compressed format with limited synchronous instruction time. The effectiveness of a human anatomy course with limited synchronous instruction time for transitional hybrid occupational therapy students was investigated. A retrospective, non-randomized study was used. A university graduate level human anatomy course for transitional OT students used prosected (previously dissected) cadavers. Students (n=46, 32 instruction hours over 16 weeks) final anatomy course grades for three cohorts were measured retrospectively. There was a 98% first-time pass rate and 100% second time pass rate. Less than 5% of the students needed to either repeat the course (one student) or withdrew from the course prior to course completion (one student). Results suggest that a hybrid learning model with limited synchronous instruction time is effective for transitional OT students learning human anatomy. Programs should consider how instruction time and distribution impacts anatomy learners, and when there is limited time in the classroom, investigate alternative pedagogies for those few students who would benefit from a more immersive-learning environment. Anatomy knowledge is essential in progressing through occupational therapy curriculums and is needed for client management. Understanding what factors impact learning anatomy could assist in creating more effective anatomy courses for occupational therapy students

Pain Relief in Older Adults Following Static Contractions is not Task-Dependent

Pain complaints increase with age. Exercise is frequently utilized for pain relief but the optimal exercise prescription to relieve pain is not clear. Following static contractions, young adults experience the greatest pain relief with low intensity, long duration contractions. The pain response to static contractions in older adults however is unknown. PURPOSE : To compare pain reports in healthy older adults before and after static contractions of varying intensity and duration. METHODS: Pain perception was assessed in 23 healthy older adults (11 men, 12 women; 72.0 ± 6.3 yrs) using a pressure pain device consisting of a 10 N force applied to the right index finger through a Lucite edge (8 x 1.5mm) for two minutes. Subjects pushed a timing device when they first felt pain (i.e., pain threshold) and rated their pain intensity every 20 seconds using a 0-10 numerical rating scale. Pain threshold and pain ratings were measured before and immediately after static contractions of the left elbow flexors at the following three doses: 1) three brief maximal voluntary contractions (MVC); 2) 25% MVC sustained for 2 minutes; and 3) 25% MVC sustained until task failure. Experimental sessions were randomized and separated by one week. RESULTS : Time to task failure for the 25% MVC contraction was 11.8 ± 5.1 minutes. A reduction in pain was found following all three tasks with no difference between tasks (trial x task effect: p \u3e 0.05), despite the duration of the 2 minute low-intensity contraction being ~17% of the contraction held to task failure. Pain thresholds for all doses increased 20% from 51 ± 33 to 61 ± 37 seconds and pain ratings averaged over the six time points decreased 20% from 3.3 ± 2.8 to 2.6 ± 2.5 following static contractions (trial effect: p \u3c 0.001 and p \u3c 0.001, respectively). CONCLUSION : Low and high intensity static contractions of both long and short duration produce similar levels of pain reduction in older adults. These preliminary data suggest that several different types of static contractions can induce significant pain relief in older adults. Age-related changes in the pain response to static contractions must be taken into account when prescribing static exercise for the management of pain

Pain Relief in Older Adults Following Static Contractions is not Task-Dependent

Pain complaints increase with age. Exercise is frequently utilized for pain relief but the optimal exercise prescription to relieve pain is not clear. Following static contractions, young adults experience the greatest pain relief with low intensity, long duration contractions. The pain response to static contractions in older adults however is unknown. PURPOSE : To compare pain reports in healthy older adults before and after static contractions of varying intensity and duration. METHODS: Pain perception was assessed in 23 healthy older adults (11 men, 12 women; 72.0 ± 6.3 yrs) using a pressure pain device consisting of a 10 N force applied to the right index finger through a Lucite edge (8 x 1.5mm) for two minutes. Subjects pushed a timing device when they first felt pain (i.e., pain threshold) and rated their pain intensity every 20 seconds using a 0-10 numerical rating scale. Pain threshold and pain ratings were measured before and immediately after static contractions of the left elbow flexors at the following three doses: 1) three brief maximal voluntary contractions (MVC); 2) 25% MVC sustained for 2 minutes; and 3) 25% MVC sustained until task failure. Experimental sessions were randomized and separated by one week. RESULTS : Time to task failure for the 25% MVC contraction was 11.8 ± 5.1 minutes. A reduction in pain was found following all three tasks with no difference between tasks (trial x task effect: p \u3e 0.05), despite the duration of the 2 minute low-intensity contraction being ~17% of the contraction held to task failure. Pain thresholds for all doses increased 20% from 51 ± 33 to 61 ± 37 seconds and pain ratings averaged over the six time points decreased 20% from 3.3 ± 2.8 to 2.6 ± 2.5 following static contractions (trial effect: p \u3c 0.001 and p \u3c 0.001, respectively). CONCLUSION : Low and high intensity static contractions of both long and short duration produce similar levels of pain reduction in older adults. These preliminary data suggest that several different types of static contractions can induce significant pain relief in older adults. Age-related changes in the pain response to static contractions must be taken into account when prescribing static exercise for the management of pain

Only Women Report Increase in Pain Threshold Following Fatiguing Contractions of the Upper Extremity

Purpose The perception of pain in response to a noxious stimulus can be markedly reduced following an acute bout of exercise [exercise-induced hypoalgesia (EIH)]. Sex differences in EIH frequently occur after exercise but may be confounded by the sex differences in muscle fatigue. The purpose was to determine if sex differences in pain relief occur after an exercise protocol when muscle fatigue is similar for both young and older men and women. Methods Pain perception of 33 men (15 young) and 31 women (19 young) was measured using a pressure pain stimulus on the left index finger before and after maximal velocity concentric contractions of knee extensors or elbow flexors (separate days). During the 2-min pressure pain test, participants verbally indicated the onset of pain (pain threshold) and reported pain intensity (0–10) every 20 s. Results Only women experienced an increase in pain threshold (30 ± 27 to 41 ± 32 s) following elbow flexor exercise (trial × sex: p = 0.03). Neither men nor women experienced an increase in pain threshold following knee extensor exercise, and pain ratings were unchanged after exercise with either limb (p \u3e 0.05). The pain response to exercise was similar in young and older adults (trial × age: p \u3e 0.05), despite older adults demonstrating greater fatigability than young adults for the elbow flexor and knee extensor exercise tasks. Conclusions 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

Relation between Pain Catastrophizing and Reporting of Pain Threshold in Healthy Adults

Participants may not consistently report pain threshold under some testing conditions. The purpose of this study was to assess the possible relations of pain catastrophizing and fear of pain to failure to report pain threshold during assessment of conditioned pain modulation (CPM). Twenty young (21.9 ± 3.3 yrs, 10 men) and 19 older (72.0 ± 4.5 yrs, 10 men) adults participated. Pressure pain was assessed using a 1.5 kg weight mounted on a Lucite edge placed on the index finger for one minute. Participants were instructed to say “pain” when the pressure first changed to pain. Pressure pain thresholds were determined with the participant’s foot placed in neutral water (non-noxious control) and in noxious ice water. Fifteen participants [10 older (7 women); 5 young (3 women)] failed to report pain threshold with their foot immersed in the ice water compared with nine [6 older (1 woman); 3 young (1 woman)] in the neutral water. Five participants failed to report pain threshold in either condition (1 older woman, 2 older men, 2 young men). Adults who failed to report pain threshold in the ice water had higher pain catastrophizing (19.2 ± 10.5 vs 10.6 ± 7.6) and greater fear of pain (14.9 ± 5.6 vs 11.5 ± 4.5) than those who said “pain”. No group differences were found for the neutral water condition. Controlling for sex, the logistic regression model containing pain catastrophizing and fear of pain was significant only for the ice water condition [χ2 (3, N=39) = 11.815, p = 0.008] explaining 26.1-35.5% of the variance. Only pain catastrophizing made a unique contribution to the model (Odds Ratio 1.10, 95% C.I. 1.004–1.208). Our data suggest that individuals with higher pain catastrophizing are more likely to fail to report pain threshold for the test stimulus when assessing CPM