***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: & NA ; Aims of investigation : To quantify the magnitude of putative gender differences in experimental pressure pain threshold ( PPT ) , and to establish the relevance of repeated measurements to any such differences . Methods : Two separate studies were undertaken . A pressure algometer was used in both studies to assess PPT in the first dorsal interosseous muscle . Force was increased at a rate of 5 N /s . In study 1 , two measurements were taken from 240 healthy volunteers ( 120 males , 120 females ; mean age 25 years ) giving a power for statistical analysis of & bgr;=0.80 at & agr;=0.01 . In study two , 30 subjects ( 15 males , 15 females mean age 28 years ) were r and omly selected from study one . Fourteen repeated PPT measurements were recorded at seven , 10 min intervals . Mean PPT data for gender groups , from both studies , were analysed using analysis of covariance with repeated measures , and age as the covariate . Results : The mean PPT for each of the two measurements in study one showed a difference between gender of 12.2 N ( f=30.5 N , m=42.7 N ) and 12.8 N ( f=29.5 N , m=42.3 N ) , respectively , representing a difference of 28 % with females exhibiting a lower threshold . In study two , the mean difference calculated from 14 PPT repeated measurements over a 1 h period was comparable to that in study one at 12.3 N ( range 10.4–14.4 N ) again females exhibited the lower threshold . The differences in mean PPT values between gender were found to be significant in both study one , at ( P<0.0005 , F=37.8 , df=1 ) and study two ( P=0.01 , F=7.6 , df=1 ) . No significant differences were found in either study with repeated measurement ( P=0.892 and P=0.280 ) , or on the interaction of gender and repeated measurement after controlling for age ( P=0.36 and P=0.62 ) . Conclusion : Healthy females exhibited significantly lower mean PPTs in the first dorsal interosseous muscle than males , which was maintained for fourteen repeated measures within a 1 h period . This difference is likely to be above clinical ly relevant levels of change , and it has clear implication s for the use of different gender subjects in laboratory based experimental design s utilising PPT as an outcome measure Introduction We aim ed to compare subjective and objective sleep quality in tension-type headache ( TTH ) patients and to evaluate the relationship between sleep quality and pain thresholds ( PT ) in controls and TTH patients . Methods A blinded cross-sectional study where polysomnography ( PSG ) and PT ( to pressure , heat and cold ) measurements were done in 20 patients with TTH ( eight episodic ( ETTH ) and twelve chronic ( CTTH ) TTH ) and 29 healthy controls .  Sleep diaries and question naires were applied . Results TTH patients had more anxiety ( p = 0.001 ) , insomnia ( p < 0.0005 ) , daytime tiredness ( p < 0.0005 ) and reduced subjective sleep quality ( p < 0.0005 ) compared to healthy controls . Sleep diaries revealed more long awakenings in TTH ( p = 0.01 ) but no total sleep-time differences . TTH patients had more slow-wave sleep ( p = 0.002 ) and less fast arousals ( p = 0.004 ) in their PSGs . CTTH subjects had lower pressure PT ( p = 0.048 ) and more daytime sleepiness than the controls ( p = 0.039 ) . Among TTH lower cold PT ( CPT ) correlated inversely with light sleep ( N1 ) ( r = −0.49 , p = 0.003 ) while slow arousals correlated inversely with headache-frequency ( r = −0.64 , p = 0.003 ) . Conclusions We hypothesize that TTH patients need more sleep than healthy controls and might be relatively sleep deprived . Inadequate sleep may also contribute to increased pain sensitivity and headache frequency in TTH Objective To evaluate interrater reliability using 5 newly trained observers in the assessment of  pressure pain threshold ( PPT )  using a fixed-angle algometer . Methods The study design comprised 2 phases . Phase 1 : 5 undergraduate physical therapists were  trained  in algometry at a predefined angle , at a rate of 5 Newtons (N)/s , to the first dorsal interosseous muscle . Each observer then underwent a competency test of the application speed . The aim was to achieve repeated applications at 5 N/s without visual feedback from the algometer . Phase 2 : the 5 observers measured PPT of 13 healthy volunteers , at the first dorsal interosseous muscle . The sequence of observer measurements for each participant was r and omized . Mean PPT values for each observer were analyzed using repeated measures analysis of variance , intraclass correlation coefficient ( ICC2,1 ) , and st and ard error of measurement , with 95 % confidence intervals ( CIs ) . Results No significant differences between observers ' mean values were found ( P=0.094 ) , suggesting no bias . The ICC was 0.91 ( 95 % CI 0.82 , 0.97 ) . The st and ard error of measurement value was 6.27 N/cm2 ( 95 % CI 5.35 , 7.59 ) . Differences in PPT measurements of more than 17.39 N/cm2 ( 1.77 kg/cm2 ) are likely to exceed the magnitude of measurement error , and could be used to indicate true change . This margin of error is , however , somewhat larger than a previously proposed minimum clinical ly important difference in PPT of 14.71 N/cm2 ( 1.5 kg/cm2 ) . Discussion This study provides new evidence that trained observers can apply an algometer at a consistent rate and provide highly reliable measures of PPT in healthy humans , when PPT is calculated as the mean of 3 trials Background The mechanisms associating sleep and migraine are unknown . No previous polysomnographic ( PSG ) or pain-threshold ( PT ) study has compared patients with sleep-related migraine attacks ( SM ) , non-sleep related migraine attacks ( NSM ) and healthy controls . Methods We have performed a blinded , prospect i ve exploratory study with case – control design . Thirty-four healthy controls , 15 patients with SM and 18 patients with NSM had interictal PSG heat-  , cold- and pressure PT ( HPT , CPT , PPT )  recordings  and completed diary- and question naire on sleep and headache related aspects . Results NSM patients had more slow-wave sleep ( SWS ) and more K-bursts than SM patients ( K-bursts : p = 0.023 and SWS : p = 0.030 ) and controls ( K-bursts : p = 0.009 and SWS : 0.041 ) . NSM patients also had lower HPT and CPT than controls ( p = 0.026 and p = 0.021 ) . In addition , SM patients had more awakenings and less D-bursts than controls ( p = 0.025 and p = 0.041 ) . ConclusionS M- and NSM patients differed in objective - , but not subjective sleep quality . NSM patients had PSG findings indicating foregoing sleep deprivation . As foregoing sleep times were normal , a relative sleep deficit might explain reduced PT among NSM patients . The SM patients had signs of slightly disturbed sleep Persistent intermittent headache is a common disorder and is often accompanied by neck aching or stiffness , which could infer a cervical contribution to headache . However , the incidence of cervicogenic headache is estimated to be 14 - 18 % of all chronic headaches , highlighting the need for clear criterion of cervical musculoskeletal impairment to identify cervicogenic headache sufferers who may benefit from treatments such as manual therapy . This study examined the presence of cervical musculoskeletal impairment in 77 subjects , 27 with cervicogenic headache , 25 with migraine with aura and 25 control subjects . Assessment s included a  photographic measure of posture , range of movement , cervical manual examination , pressure pain thresholds , muscle length , performance in the cranio-cervical flexion test and cervical kinaesthetic sense .  The results indicated that when compared to the migraine with aura and control groups who scored similarly in the tests , the cervicogenic headache group had less range of cervical flexion/extension ( P=0.048 ) and significantly higher incidences of painful upper cervical joint dysfunction assessed by manual examination ( all P<0.05 ) and muscle tightness ( P<0.05 ) . Sternocleidomastoid normalized EMG values were higher in the latter three stages of the cranio-cervical flexion test although they failed to reach significance . There were no between group differences for other measures . A discriminant analysis revealed that manual examination could discriminate the cervicogenic headache group from the other subjects ( migraine with aura and control subjects combined ) with an 80 % sensitivity Background Quantitative sensory testing , including  pressure pain threshold ( PPT ) , is seeing increased use in clinical practice . In order to facilitate clinical utility , knowledge of the properties of the tool and interpretation of results are required . Objectives This observational study used a clinical sample of people with mechanical neck pain to determine : ( 1 ) the influence of number of testing repetitions on measurement properties , ( 2 ) reliability and minimum clinical ly important difference , and ( 3 ) associations between PPT and key psychological constructs . Design This study was observational with both cross-sectional and prospect i ve elements . Methods Experienced clinicians measured  PPT  in patients with mechanical neck pain following a st and ardized protocol . Subcohorts also provided repeated measures and completed scales of key psychological constructs . Results The total sample was 206 participants , but not all participants provided data for all analyses . Interrater and 1-week test-retest reliability were excellent ( intraclass correlation coefficients [2,1]=.75–.95 ) . Potentially important differences in reliability and PPT scores were found when using only 1 or 2 repeated measures compared with all 3 . The PPT over a distal location ( tibialis anterior muscle ) was not adequately responsive in this sample , but the local site ( upper trapezius muscle ) was responsive and may be useful as part of a protocol to evaluate clinical change . Sensitivity values ( range=0.08–0.50 ) and specificity values ( range=0.82–0.97 ) for a range of change scores are presented . Depression , catastrophizing , and kinesiophobia were able to explain small but statistically significant variance in local PPT ( 3.9%–5.9 % ) , but only catastrophizing and kinesiophobia explained significant variance in the distal PPT ( 3.6 % and 2.9 % , respectively ) . Limitations Limitations of the study include multiple raters , unknown recruitment rates , and unknown measurement properties at sites other than those tested here . Conclusions The results suggest that PPT is adequately reliable and that 3 measurements should be taken to maximize measurement properties . The variance explained by the psychological variables was small but significant for 3 constructs related to catastrophizing , depression , and fear of movement . Clinical implication s for application and interpretation of PPT are discussed 
    Output:
    
Most studies found no association between PPT values and headache characteristics such as frequency , duration or intensity .