The Male Orgasm: Pelvic Contractions Measured by Anal Probe

Transcription

1 Archives of Sexal Behavior, Vol. 9, No. 6, 198 The Male Orgasm: Pelvic Contractions Measred by Anal Probe Joseph G. Bohlen, M. D., Ph. D., ''3 James P. Held, B.Ch. E.,1'2 and Margaret Olwen Sanderson, M.D. 2 Pelvic mscle contractions dring sexal response can be monitored conveniently by the anal probe method described. Eleven yong adlt male sbjects were each recorded for three sessions of mastrbation to orgasm. Electrical signals from an anal pressre probe were atomatically digitized by compter. Orgasmic contractions were easily distingished from volntary contractions by the steadily increasing intervals and complete mscle relaxation between orgasmic contractions. At orgasm each sbject prodced a characteristic series of contractions starting abrptly at an intercontraction interval of abot.6 seconds, and contined for 1 to 15 contractions at an increasing increment of abot.1 second per contraction. Pressre amplitde, representing the force of contractions, increased from the beginning of the reglaf'\ series to a maximm at the seventh or eighth contraction. Area nder the pressre crve, reflecting msclar exertion dring contraction, generally increased throghot the reglar series. Each man's pattern of contractions was very similar from one session to the next and distingished his records from others'. ndividals' patterns cold be groped into three types, based chiefly on the location of the reglar contraction series within the sbjective span of This research was spported by grant MH from the National nstitte of Mental Health. 'Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, Minnesota 'Department of Family Practice and Commnity Health, University of Minnesota Medical School, Minneapolis, Minnesota 'Address correspondence to Dr. Joseph G. Bohlen, Physiology Research Laboratory, Site 315, University Park Plaza, 2829 University Avene SE, Minneapolis, Minnesota /8/12-53$3./ 198 Plenm Pblishing Corporation

2 54 Bohlen, Held, and Sanderson orgasm. The most common type was a simple series of reglar contractions. t had the shortest dration and fewest contractions. The next most common pattern began with the reglar series, followed by a nmber of irreglar contractions. This type was longest in dration. One man with a third type, of intermediate dration, had a nmber of preliminary contractions before the series of reglar contractions began in midorgasm. KEY WORDS: male sexal response; pelvic contractions; orgasm; mastrbation; anal probe. NTRODUCTON For it is impossible to emit semen withot contracting the parts abot the fndament [i:dea, ans]... The contraction of the bttocks forces ot the moistre... Sch moistre flows into the fndament; for it passes in this direction. This is proved by the contraction of this part in intercorse and the softening of the parts abot the fndament. Aristotle, ca 4th centry B.C. Aristotle recognized 24 centries ago that the ans was a significant site of sexal response. Kinsey et al. (1953) wrote that the importance of the anal area in sexal response of both men and women was related to the mscles commonly shared with the respective genital areas. Detailed observations dring orgasm made by Masters and Johnson (1966) frther described the representative response of the ans in both genders. They fond that dring orgasm the anal contractions were synchronized with the vaginal contractions and with the explsive penile contractions. The pelvic msclatre that enables the ans to respond in parallel with the male and female genitalia shares a common nerve spply4 (Hollingshead, 1974; Bacon and Recio, 1962). 'The sphincteric action of the msclar cylinder arond the anal canal is created by the levator ani and the internal and external anal sphincters. Forming the blk of the pelvic diaphragm is the levator ani, with indistinct sbdivisions: the pborectalis, pbococcyges, and iliococcyges mscles. The pborectalis and pbococcyges portions srrond and firmly attach to the anal canal and rethra (Hollingshead, 1974). As a nit, the levator ani mscle is innervated by twigs from the second throgh forth sacral nerves via direct mscle branches from the plexs and throgh the perinea! branch of the inferior hemorrhoidal nerve (Bacon and Recio, 1962). The anal sphincters are located distal to the levator ani. The internal anal sphincter, of smooth mscle, encircles the pper two-thirds of the anal canal. Below it is the external anal sphincter, a volntary mscle srronding the lower two-thirds of the anal canal. Portions of it merge with the blbocavernoss mscle of the penis. The deeper portion is inseparably attached to the pbococcyges mscle. The anal sphincters are also innervated by the inferior hemorrhoidal nerve from the third and forth sacral nerves (Bacon and Recio, 1962).

3 Pelvic Contractions in Male Orgasm 55 The ans affords several advantages as a site for recording representative msclar events dring sexal response. A probe in this location interferes minimally with genital stimlation in either men or women and also allows direct gender comparison of mscle tension and contractions. Techniqes for anal monitoring can be modeled on those developed for measring vaginal mscle tension, for example, changes in air pressre within a pnematic cylinder (Kegel, 1952; Logan, 1975) or a balloon (Jovanovic, 1971; Campbell, 1976). The first direct and precise measrement of anal msclar contractions at orgasm was made over a decade ago (Kollberg et al., 1962; Petersen and Stener, 197; Kadefors and Petersen, 197). ndividal pelvic mscles were monitored electromyographically by coaxial needle electrodes. Using this method the researchers were able to isolate responses of the individal msdes. Their EMG recordings dring orgasm showed that the involntary contractions were discrete brsts of activity, separated by electrical silences. This characteristic was synchronized among the striated rethral sphincter, sphincter ani, and levator ani mscles, and most prominent in the rethral sphincter. A less invasive method for measring pelvic msclar events dring sexal response is with an anal probe (Bohlen and Held, 1979). Gross pressre changes of an air chamber retained in the anal canal provide qantitative data that represent general msclar responses. The probe calibration in nits of cm H2 and configration for repeated measrement of the same examining site enable direct comparison across experimental sessions and sbjects. This paper will describe a stdy with sch a probe of anal contractions in men. The prpose of the stdy is to develop a method for describing contractions dring orgasm. Waveforms of contractions can be analyzed for parameters that represent physiologic properties of the anal msclatre. The data can then be sed to determine the variability of each sbject's orgasmic experience and to classify contraction patterns. Sch detailed analyses of pelvic contractions may lead to a better nderstanding of the neromsclar changes dring sexal response in healthy individals. Knowledge of the nderlying mechanisms can then be applied to recognizing sexal dysfnctions that may have a neromsclar basis. METHODOLOGY Recritment and Orientation of Sbjects Recritment presentations were made in several medical school classes and gradate level corses on hman sexality at the University of

4 56 Bohlen, Held, and Sanderson Minnesota. Some men also volnteered for the stdy after learning abot it from the researchers or from previos sbjects. Sbjects were screened for self-defined physical, mental, and sexal health, appropriate age, and ability to mastrbate to orgasm. The orientation process was divided into for separate sessions of 1 to 2 hors each. Two researchers (JGB and MOS) were involved in the steps of the orientation process; JGB assmed the role of primary interviewer for this stdy of male sbjects. At the first appointment a sbject was presented the overall goals and relevance of the research, and the steps of orientation. Safegards against potential hazards were described for his physical and psychological protection. These steps inclded a check of the electronic eqipment by a biomedical engineer to garantee that no crrent cold accidentally be condcted to the sbject, sterilization of the anal probe to prevent cross-infection among sbjects, and availability of psychological assistance if an individal responded adversely to the experiment. Potential benefits to the sbject were otlined. Participation cold frnish a free physical and genital examination, increase the man's knowledge of physiology and anatomy, provide an nderstanding of his own sexal response, and give him the personal satisfaction that his contribtion might advance scientific knowledge in the area of hman sexal response. The sbject was told that he wold not receive a financial remneration. Anonymity was assred; his identity wold be protected by code nmbers. The sbject was told that he cold withhold any information dring the orientation process. Then he was given a laboratory tor dring which instrment placement was explained and privacy dring ndressing and data collection was described. The sbject was encoraged to ask qestions at this and sbseqent orientation appointments. At the second and third appointments the researchers condcted a two-part sex history interview with the sbject. He was also given a consent form to sign at the second visit. At the forth orientation appointment the sbject filled ot a brief medical history form. Then he received a medical examination by two physicians (JGB and MOS). A rotine general exam emphasized health screening appropriate to the sbject's age. An extensive genital examination described his individal anatomy. Following the physical examination he engaged in a private mastrbation session. This opportnity was intended to redce the sbject's anxiety in sbseqent laboratory sessions that wold be physiologically monitored. A sheet of instrctions was given to him detailing instrment placement and procedres followed dring the monitored sessions.

5 Pelvic Contractions in Male Orgasm 57 Sbjects Eleven male volnteers between the ages of 24 and 35 (average age of 28.5 years) were selected for this stdy. Reslts of physical examinations for each were well within the limits for healthy yong men. One sbject had been on Synthroid medication (. 15 mg.) for 1 year following treatment for hyperthyroidism. Genital examinations did not reveal congenital anomalies or any other nsal characteristics except for a varicocoele in one man. Nine were circmcized; none had vasectomies. All sbjects commonly sed genital self-stimlation as a method of sexal gratification. Total sexal otlets to orgasm averaged 4. 7 times dring the week preceding an individal's session. All of the sbjects were Cacasian, middle class, and professional or in a professional degree program. Eight of them were married or in other long-term relationships. Sexal preference of all the men was heterosexal. Empirical scores on the Tennessee Self Concept Scale were within normal limits except for one individal whose score was sbstantially above the normal range on the defensive positive score. Experimental Design Each sbject was recorded on three different occasions, if possible at the same time of day. (Occasionally a sbject was not able to participate in all three rns at the same time of day.) The sessions were as freqent as on sccessive days or, in one case, as separated as 17 days. These data were smmarized by simple averaging, ths disregarding any possible rhythmic or interval effects. Nevertheless, all times and dates were recorded to allow ftre investigation of these effects. On the few occasions when there was mechanical, electrical, or compter malfnction dring one of the sessions the rn was reschedled; ths some of the sessions reported here might not have been the consective times that a sbject was recorded. Prior to an individal's recorded session, the sbject first had a presession interview and completed a six-item assessment of crrent sexal interest. Then he retired to the experiment room and completely ndressed in privacy. Two of the researchers (JGB and MOS) entered the experiment room and affixed the transdcers. A few sbjects reported slight discomfort on insertion of the probe, bt this sbsided dring the setp stage. Besides anal mscle tension, circmference of the penile base, heart and respiratory rates, skin condctance, and photoplethysmographic blood volme and

6 58 Bohlen, Held, and Sanderson blood volme plse were monitored. Once the researchers were assred that all variables were being recorded properly, they left the room. The sbject lay spine on a bed dring recording. Room temperatre cold be reglated by the sbject and a light blanket sed for physical comfort. Commnication with the sbject dring the remainder of the rn was only by intercom; he was never observed dring the recorded session. A premastrbation level of maximal volntary anal contraction was obtained. Three separate pelvic contractions were reqested, to be done as strongly as possible withot an accompanying Valsalva manever. The sbject was then instrcted to relax for 5 mintes of recorded resting baseline. At the end of that span he began mastrbation, maintaining a steady bildp of arosal to orgasm, if possible. Mastrbation was manal withot any other devices. Artificial lbrication was permitted.. Sexal fantasies accompanying mastrbation were assmed to be a normal part of the self-stimlation process, bt erotic materials were not allowed dring the session. Orgasm was defined sbjectively by the individal. The man was instrcted to press an event marker btton the instant he perceived orgasm starting, and a second time when he felt it was over. Five mintes of post-orgasm recovery was recorded with him relaxed and motionless. Then three volntary post-orgasm pelvic contractiop.s were reqested. Data recording terminated and the man removed the transdcers, cleaned p, and dressed. mmediately afterwards he completed a nine-item qestionnaire rating the orgasm's intensity and dration. Finally he was interviewed abot perceived physiologic changes dring the sexal response. Between sessions, the anal probe and mercry strain gage were chemically sterilized by washing in soap and water, washing with Betadine soltion, and soaking in Cidex-7 soltion for a minimm of 1 mintes. nstrmentation and Recording Changes in pelvic mscle tension associated with orgasm were monitored with an anal probe (Bohlen and Held, 1979). A pressre transdcer in a closed air chamber in the probe neck measred changes in mscle tension of the sphincter ani and levator ani complex. The probe's configration permitted it to fit comfortably within the anal canal, minimize motion artifact, and reliably record the same anatomical site across sessions and sbjects. The sbjective experience of orgasm was demarcated by sbjects' se of an event marker. Signals from the pressre transdcer and event marker were transmitted directly to a strip chart recorder (Beckman Type R Dynograph), where the pressre signals were amplified (Beckman amplifier 485) and

7 Pelvic Contractions in Male Orgasm 59 bandpass filtered. Signals contined to an on-line real-time compter system (D.E.C. PDP-11/4) with analog-to-digital converter sbsystem (AR-11). Digitization of the pressre signals at the rate of 1 samples per second5 captred the principal featres of waveforms, and these vales were stored on flexible diskettes. After each rn the probe's air chamber was vented to the atmosphere. The eqilibrated pressre ( cm H2, gage) was recorded as an ambient pressre standard. This vale, pls knowledge of the amplification, offset, and pressre/voltage crve of the transdcer, permitted comptation of real pressre vales (cm H2) from the stored digitized data. Data Analysis Orgasm was characterized by a series of reglar anal contractions and, in some sbjects, additional irreglar contractions. A compter program to describe nmerically for parameters of these contractions (named below) was written by one of the athors (JPH). The program scans the original pressre data and locates contractions with peaks greater than a specified minimm amplitde. Contractions are then nmbered consectively and these parameters are calclated to describe each one (Fig. 1): ntercontraction interval is the time in seconds between the peak of one contraction and the next. Amplitde of a contraction is the vertical distance in cm H2 between the peak vale and the average of the minima on either side. Area for a contraction incldes all the vertical space from (ambient pressre) to that bonded by the contraction, in nits of cm H2 X time. Net area for a contraction is the space bonded only by the change in pressre de to the contraction above the line joining the minima on either side, in nits of cm H2 X time. These for parameters were calclated for each contraction that occrred dring an orgasm. Then parameters were averaged for each sccessive contraction across the three sessions of a sbject. Finally, the contraction averages of three rns from a sbject were sed to compte smmaries across individals. Dration of sbjective orgasm was calclated (in nits of. 1 second) from the individal's event markers of start and end of orgasm. Nmber of orgasmic contractions was compted by specifying threshold criteria for their detection in each session. 'This data collection rate has sbseqently been increased to 2 samples per second to provide a sbstantial margin for precision.

8 51 Bohlen, Held, and Sanderson 2SQ nterval CJ N ::c 2= 15'1... UJ :: :::) <..n <..n UJ :: lllo a.. z CJ 1- cc :: 5 1- z CJ Contraction Nmber Net Area J r 2 6 TME CSECONOS) 8 Fig. 1. Parameters compted on each separate orgasmic contraction. RESULTS Series of Reglar Contractions The anal contractions dring orgasm are distinctive and discrete from the anal tension of mastrbation and post-orgasmic relaxation, as illstrated by the typical recording in Fig. 2. Throghot mastrbation the anal tension is irreglar, perhaps reslting in part from pelvic movements and volntary straining. Contractions are nevenly spaced and have varying amplitdes and shapes. With the onset of orgasm, however, a series of

9 D N :L s es z w a::: ::J (J) (J) w21111 a::: Q_ ";! 3: n 6'l a g. = "' 5 a::!.... i 5 z D f a: 1118 a::: f z D,l Relaxation , Mastrbation Orgasm --, , f see ELAPSED TME N SECONDS T a111 Relaxation , 888 Fig. 2. Compter drawn plot of anal tension and contractions representing portions of a sbject's recorded session: resting baseline tension; irreglar tension and contractions dring mastrbation; series of reglar contractions at orgasm (black triangles indicate signalled onset and end of orgasm); and resmption of resting baseline tension immediately after orgasm. "'.....

10 512 Bohlen, Held, and Sanderson reglar consective contractions begins abrptly, with similar amplitdes and waveforms. Abot 1 to 15 contractions occr in a reglar and rapid seqence, with progressively greater separation between them as the orgasm contines. Usally there is a distinct termination of contractions at the end of orgasm. The series of reglar contractions occrs in all sbjects, althogh in some sbjects additional irreglar contractions are inclded in the sbject's experience of orgasm. nspection of single reglar contractions on an expanded time scale reveals a 'distinctive appearance (Fig. 3a). A contraction dring the first part 399 a N 1118 :r :L z LLl 899 a:: :::l (.J) (.J) 299 LLl a:: z f-- C :: Ull f-z g B c a TME N SECONDS Fig. 3. Anal contractions dring (a) orgasm, (b) maximal volntary effort, and (c) rapid volntary effort at 3, 2, and 1 times per second.

11 Pelvic Contractions in Male Orgasm 513 of orgasm rises rapidly to a peak, then swiftly descends to a trogh. Recovery from a contraction is rapid and is followed directly by the next contraction. The speed and completeness of relaxation, even descending below baseline tension, contrasts with the gradal relaxation of a volntary contraction in Fig. 3b. While initial contractions have sharp peaks and troghs, later peaks and troghs begin to broaden. Toward the end of orgasm the relaxation to baseline with each contraction is less rapid and begins to approach the gradal relaxation of volntary contractions. Three attempts to replicate volntarily the rapid contractions of orgasm are illstrated in Fig. 3c. The repeated volntary contractions differ from orgasmic contractions in being nable to retrn completely to baseline between contractions. Amplitde does not maintain a steady level as it does dring orgasm, bt diminishes in sccessive volntary contractions. The progressive decrease in freqency of orgasmic contractions is difficlt to reprodce volntarily. Contraction Patterns The series of reglar contractions is immediately recognized in each of the examples in Fig. 4. n six sbjects, the series of reglar contractions constittes the entire orgasm, as represented by one man's three sessions in Fig. 4,1. Another for men begin orgasm with a series of reglar contractions, bt the reglarity deteriorates after 1 to 15 contractions (Fig. 4,11). Sbseqent contractions dring the remainder of the orgasm vary in intercontraction interval, amplitde, and wave shape. These irreglar contractions in the second type are more similar in shape to the example of volntary contractions in Fig. 3b. rreglar contractions might be solely involntary, or they may be partially volntary in accompaniment to those individals' orgasmic experience. Regardless, these men inclded both the reglar series of contractions and the involntary contractions within the perceived span of orgasm. Lastly, one man's orgasms start with abot seven to nine initial contractions, are interrpted by sstained tension with a few broad contractions for for to five seconds, then are followed by the series of reglar contractions that contines to the end of orgasm (Fig. 4,). These three patterns exhibit qantitative differences in orgasm length and nmber of contractions (Table ). The most common pattern () fond in the stdy is briefest and comprises the fewest contractions. The next most common pattern () shows orgasms that are two or three times longer and comprise abot twice as many contractions. The one sbject with a third pattern has orgasms intermediate in length, bt with as many contractions as in pattern.

12 . t. '1";.:: SQ8 \ 1 1 m '"t 'nll., '\. ' h 11 '\-_,-" N.. A ll S U 15 '2ll U 1.S ;1 7S 61 1 ' ,'1' " _, '----'- - ::t : _L '. '. ' '- H ',,.... _ { - " t.r ,,..._ _- S ll S ' lff S se SS i n,, - ;.,' -' 1'. l -. i 11,.r & S &9-11"'1 l '. \../',,1.., \_ /1.""\ '\' 11., \ '-'., "' '--.,-...,....., \. ' L 15 r----r :S 5 -, 11 -, '" C\J E.s: (1).. :: ti) ti) (1)..... c:: ti c,_ - c '..: 1" '"'t -- \ :1.. "a s 15 '2 s 3'.. ".., ' \ '",,. ', :i.s s Sil SM : '., 'il l'. ' \ ' '. --., y ' ;. '.'.. S " " " :i : ' ' 1. 'v. 11 """ HB '-, ''\ '.._ -- " ti - ---,--. o---r a :!l 25 1)11 3S ll f,,. \ 1111' L,,... ' ',111 ii 1$8,,,,,.,, dj,,... ', ', \ \ :,_ "J<..., \1 \ \ \ ' ".. & U 7'4 \,, r- "",---r , S H S Se SS 6i' -.,./ '/-, _,., ,. 'tl --..._.,, ,..--i W &S lb L E < 31la,,,: '.,1'.. 1. " 2911 '..,-, ' ' /...,,,, 'i1,., / :- l "' a i a s a is :n- S SQ 35 ' ",J " ' " "" ;i.. " " " :l:n on ' ' 11 1,, 1,,1 ",,, a. '- -r ia 1s '(Q '(5 3Q 35 i,a >S Time in seconds 55 6il GS Fig. 4. Anal contractions of sbjects representing three contraction patterns (,, and ) recognized at orgasm. Three replicates by each sbject demonstrate the consistency of individal response. Black triangles indicate sbjective start and end of orgasm, not necessarily coincident with start and end of anal contractions.

13 Pelvic Contractions in Male Orgasm 515 Table. Average Characteristics of Men's Anal Contractions Dring Orgasms of Three Pattern Typesa Pattern type All sbjects Nmber of sbjects Dration of SD 8.8 SD 17.6 SD17.2 orgasm, sec range range range Nmber of SD4 SD 9 SD 8 contractions range 8-18 range range 8-33 abased on data from individal averages of three sessions; hence one sbject representing pattern does not have dispersion indices. The similar appearance that anal contractions of three individals exhibit from one orgasm to the next is evident in Fig. 4. These records, which are representative of the patterns fond in the stdy, illstrate the consistency of dration of orgasm, nmber and height of contractions, and orgasm markers relative to anal contractions. The figre also shows that the characteristics that are repeatable within each sbject differ slightly among individals. Each man has a distingishing appearance of orgasmic contractions. Contraction Parameters Average contraction parameters for the sbjects with the three orgasm types are displayed in Fig. 5. n five men of patterns and the start of reglar contractions consistently begins more than 1 second before orgasm is signalled by the sbjects. Five other men have contractions that begin less than a second before or after the orgasm signal. For those 1 cases, calclation of contraction parameters commences with the onset of each series of reglar contractions. For the type sbject, orgasms are aligned so that the onsets of reglar contractions in midorgasm coincide. ntercontraction intervals of the reglar contraction series in Fig. 5 are strikingly similar across individals with all three types of pattern. The interval begins at a vale of less than 1 second and increases in an almost linear fashion over 1 to 15 contractions with an average increment of abot.1 second. (Note that the reglar contractions in type are taken to begin on the 12th contraction.) There are only small differences among individals' averages dring the reglar series of contractions, as indicated by the small standard deviations for individals' three-session averages. After the series of reglar contractions in type, the linear trend is lost and the

14 lntercontraction nterval Clo '" X±/SD 3 Amplitde 2 '" -j.o,",' '""" jl 5 ::: "t 1 Area ldtroooo 1 tt+#htf r?.kll1!'-,\,l 1" 11 ltl S "tt#tttm tt o c Net Area ':i? +--,--, ls W ') l'j 2 1,1,,t\i11ttil1l1\ l o c' -h- lcc<-? s : is 2"1 2s :3e 3 : l\j!ljjjl\j\itf1t 11 1,,,,! : 4111tt*j lj 1 rt111l, : -h- 5!!S 2?. 3 3S 1!') /!fl c (J) V ''"" ' i. : i 1 j1tt,11: t tl,. ttlli 11. (\J ' 1 ' id> : so li t E rr " tt:'. $ o '!,, <> o o -r--.-.-,- -,----,--,-.---, s " 3 3=; ll v:..-p cc cc cp 3 7. CD Hl O o<:x? oo Oci:J 5'il C 9 3 c WVJ, o cp COoc o O c oco ''<l--l«pi::p Ll:'.li!l-,,. Oo 5 ct> c" OJ o vc oc CJ c.: c r t '.!" '2 L. --t-- -,,,... 1(.?i \':, w 2: -,-r-.,..., '.S? 2<; 1t-r---1- r - -r r..,..._.,,- ' 'S 2 2": Nmber of Contractions Fig. 5. Parameter averages of orgasmic anal contractions in patterns,, and H. Dispersion lines are among individals' averages for three sessions. Circles withot dispersion indices indicate contractions from one sbject.

15 Pelvic Contmctions in Male Orgasm 517 indices of dispersion are several times greater than in previos contractions. n type the nonniform contractions occr in the first half of the orgasm. ntervals that are less than 1 second for the first eight contractions lengthen p to 2 seconds dring the sstained contractions prior to the onset of reglar contractions. Amplitde of the series of reglar contractions (Fig. 5) increases from the first to the seventh or eighth contraction before leveling off and decreasing. The large dispersion bars in amplitde do not reflect scatter within sbjects, bt rather systematic differences among people. The amplitde plots of individals demonstrate the same smoothness of crve p, across, and down for the series of reglar contractions. The differences in average level of amplitde among individals contribte most to the large SD for contractions. Two individals of pattern with high amplitdes in contractions 11 and 12 interrpt the smooth trend in that grop's pattern. n sbjects with pattern, the amplitdes do not show any consistent trend after the end of the series of reglar contractions. The man with pattern displays amplitdes of intermediate vale prior to the start of reglar contractions. Plots of average area and average net area in Fig. 5 show similar trends for all three patterns dring the series of reglar contractions. n both parameters the initial reglar contractions begin at low levels, reflecting the narrow contractions at the beginning of the series. ncreasingly greater areas accompany later contractions as they broaden. At the end of abot a dozen contractions, area and net area become highly variable. n the men with pattern the later irreglar contractions vary in vale and in size of dispersion indices. The initial contractions of the pattern man have small areas and net areas. Then high vales reslt from the sstained contractions jst prior to the start of his reglar contraction series. DSCUSSON The series of reglar orgasmic contractions, as monitored conveniently by anal probe, has an abrpt onset and termination. Sbjective perception of orgasm is associated with the contraction series, bt does not correspond precisely to it. The start of orgasm for some men coincides with the initial contractions; for others the perceived onset consistently precedes or follows the first reglar contractions by several seconds. Petersen and Stener (197) also noted individal differences in the interval from the signalled onset of orgasm to the start of the first reglar contraction. This varied from.2 seconds to 7. seconds in seven sbjects.

16 518 Bohlen, Held, and Sanderson When some of their volnteers were monitored a second time, the intervals were similar to those recorded earlier on the same individals. The relationship between perceived start of orgasm and the onset of the series of reglar contractions will be discssed in a ftre paper. The average total nmber of contractions per orgasm of all men in this stdy is 17, comparing closely with a range of 15-2 contractions in the Kollberg et al. (1962) stdy. Other investigators did not record contractions, nor did they sggest that sch a large nmber occrs. Kinsey et al. (1953) stated that the anal sphincter opened and closed rhythmically at orgasm, bt did not indicate the nmber of contractions that occrred. Masters and Johnson (1963) reported that not more than two to for anal contractions sally occr in men. This discrepancy in contraction nmber between their observations and this recorded data may be attribtable to the difficlty of observing contractions that are occrring rapidly (at intervals initially arond.6 seconds) and deep within the anal canal where they may not always be perceived from the p.erianal srface. Orgasm dration in men is qantified by few researchers. Neither Kinsey et al. (1948) nor Masters and Johnson (1963, 1966) reported the length of orgasm. Masters and Johnson (1966) explained that "the orgasmic phase is limited to those few seconds dring which the vasocongestion and myotonia developed from sexal stimli are released." Kollberg et al. (1962) briefly mentioned that among their 12 male sbjects ejaclation lasted approximately 25 seconds. Their vale corresponds qite well to the average orgasm dration of 25.8 seconds in the present stdy. n addition, this stdy demonstrates that length of orgasm is related to type of contraction pattern. The repeatability of the general pattern of orgasm contractions in a sbject among his three sessions is evident (Fig. 4). This stability is a theme that has been toched on by several researchers. Laboratory observations by Masters and Johnson (1963) determined that whether men responded to coits, mastrbation, or being mastrbated, researchers detected "no consistent variation in the male response patterns related specifically to any of the three different modes of sexal stimlation." Kinsey et al. (1948) reported longitdinal observation by a few interviewees that sggested "the particlar type of orgasm experienced by a yonger boy remains as his particlar type into his adlt years. The variation in pattern of orgastic response ths seems to depend, at least to some degree (and in the limited nmber of cases so far stdied), on inherent differences in the biological constittion of different individals." The for contraction parameters that are smmarized for the pattern types may have physiologic relationships. First, the intercontraction interval reflects the rapidity with which the sphincter mscles can contract,

17 Pelvic Contractions in Male Orgasm 519 completely relax, and contract again. The data described in this paper show that the intervals between sccessive contractions are initially shorter than can be replicated volntarily, and increase at a linear rate. The average beginning interval is abot.6 seconds, lengthening in sbseqent contractions at an increment of abot. 1 seconds per contraction. Masters and Johnson (1963, 1966) described the initial several anal contractions occrring at an interval of approximately.8 seconds. After two to for contractions, they reported that the contractions cold no longer be seen, thogh the explsive rethral contractions contined at a "marked redction in rapidity of occrrence.' ; (From that description one is ncertain whether Masters and Johnson meant a drop in freqency to a new steady rate or a progressive decrease in freqency.) Petersen and Stener (197) qantified the intervals of anal contractions at orgasm. From their EMO records they cold examine the electrical activity and silence separately. Least-sqares fitting of slopes for a graph of interval vs. contraction nmber showed that activity and silence dration both increased from contraction to contraction at abot the same rate (.34 seconds/contraction for EMO activity and.39 seconds/ contraction for electrical silence). Ths, Petersen and Stener demonstrated that the progressive increase in intercontraction interval at orgasm is not merely the reslt of identical contractions spaced farther apart, nor of sccessively longer contractions separated by relaxation of niform dration, bt a combination of steadily lengthening contractions and relaxations (i.e., a generally broadened waveform). To compare their EMO intervals with the anal pressre data described in this stdy, the average spans of electrical activity and of silence were added for each contraction in the data of the Petersen and Stener (197) stdy. When a regression analysis is performed on the sccessive contraction intervals ths obtained, the reslting. eqation of linear regression is fn N, where N is the intercontraction interval = (in seconds) and N is the contraction nmber, starting with 1. The linear regression eqation for all the individal contraction intervals in the crrent stdy (regardless of pattern) is very similar: N N. Ths, in = two separate male samples measred by different techniqes, the initial intervals between msclar contractions at onset of orgasm and the rate at which the intervals increased are repeatable. The small differences in slope fond for different individals (Fig. 5) sggest that the orgasmic contractions may be timed by a highly specific neromsclar mechanism. Frther research is necessary to determine whether sch an inference is warranted. The second parameter, amplitde, represents strength (maximm msclar force) of the contractions. Dring the series of reglar

18 52 Bohlen, Held, and Sanderson contractions in men, anal strength is low at the onset, gets progressively stronger, and levels off at abot the seventh or eighth reglar contraction. Over the next several contractions, sphincter strength diminishes. Masters and Johnson (1966) stated that the explsive force of penile contractions is greatest at the onset of orgasm and rapidly diminishes after the first three or for major explsive efforts. Withot knowledge of their method of measring explsive force, it is difficlt to determine whether or reslts differ from theirs or represent a separate physiologic process. Area and net area reflect mscle exertion (msclar force over time) dring contractions.6 Area incldes the exertion reqired to maintain mscle tone abot the anal probe, as well as to prodce the contraction. Net area (above baseline) represents the msclar exertion of the contraction only. nitial contractions of the reglar series have the lowest expended energy of orgasmic contractions. The mscle exertion increases steadily in sbseqent contractions to a peak at abot the 1th or 12th contraction. f the individal orgasm and nmber of contractions extend past that point, the msclar exertion decreases and becomes more variable from contraction to contraction. Location of the series of reglar contractions within the span of orgasm has been sed to categorize patterns into three recognizable types. Additional types may emerge as more individals are monitored. This classification was based solely pon gross appearance of contraction patterns and does not necessarily represent any nderlying physiologic distinctions. t may reflect a variety of other factors, for example, differences in self-stimlation techniqes. By sing in this work a monitoring techniqe that measres responses in the ans we do not intend to sggest that orgasms have primary focs there. The anal site for measring general pelvic mscle changes was chosen becase of its representative response and the potential comparability between genders. For ftre research on the physiology of sexal response this method may be sefl in comparing the orgasmic responses in coits with those in mastrbation, determining the effects of aging on pelvic contractions, comparing men's msclar responses with women's, contrasting variation of contraction parameters within and among individals, and relating sbjective experience of orgasm to the objective physiologic measres. Area and net area are directly compted from the data records and correspond in a general way with msclar exertion. More conceptally rigoros parameters are being considered.

19 Pelvic Contractions in Male Orgasm 521 ACKNOWLEDGMENTS The athors express their appreciation to Andrew Ahlgren, Ed.D., Associate Director, Center for Edcational Development, University of Minnesota, for his provocative discssions abot the research and helpfl sggestions for this manscript, and to Barbara Britson for her secretarial contribtions. REFERENCES Aristotle (ca 4th centry B.C.). Problems, Book V, trans. W. S. Hett. Heinemann, London (1936), pp. 19, 127. Bacon, H. E., and Recio, P. M. (1962). Srgical Anatomy of the Colon, Rectm and Anal Canal. Lippincott, Philadelphia. Bohlen, J. G., and Held, J.P. (1979). An anal probe for monitoring vasclar and msclar events dring sexal response. Psychophysiology 16: Campbell, B. (1976). Nerophysiology of the clitoris. n Lowry, T. P., and Lowry, T. S. (eds.), The Clitoris, Warren H. Green, St. Lois. Hollingshead, W. H. (1974). Textbook of Anatomy. Harper and Row, New York. Jovanovic, U. J. (1971). The recording of physiological evidence of genital arosal in hman males and females. Arch. Sex. Behav. 1: Kadefors, R., and Petersen,. (197). Spectral analysis of myo-electric signals from mscles of the pelvic floor dring volntary contraction and dring reflex contractions connected with ejaclation. Electromyography 1: Kegel, A. H. (1952). Sexal fnctions of the pbococcyges mscle. West. J. Srg. Obstet. Gynecol. 6: Kinsey, A. C., Pomeroy, W. B., and Martin, C. E. (1948). Sexal Behavior in the Hman Male. W. B. Sanders, Philadelphia. Kinsey, A. C., Pomeroy, W. B., Martin, C. E., and Gebhard, P.H. (1953). Sexal Behavior in the Hman Female. W. B. Sanders, Philadelphia. Kollberg, S., Petersen,., and Stener,. (1962). Preliminary reslts of an electromyographic stdy of ejaclation. Acta Chir. Scand. 123: Logan, T. G. (1975). The vaginal clasp. A method of comparing contractions across sbjects. J. Sex Res. 11: Masters, W. H., and Johnson, V. E. (1963). The sexal response of the hman male.. Gross anatomic considerations. West. J. Srg. Obstet. Gynecol. 71: Masters, W. H., and Johnson, V. E. (1966). Hman Sexal Response. Little, Brown, Boston. Petersen,., and Stener,. (197). An electromyographical stdy of the striated rethral sphincter, striated anal sphincter, and the levator ani mscle dring ejaclation. Electromyography 1: