224 BrJ Sports Med 1997;31:224-228

Energy expenditure and physiological responses during indoor rock climbing Br J Sports Med: first published as 10.1136/bjsm.31.3.224 on 1 September 1997. Downloaded from

Christine M Mermier, Robert A Robergs, Susie M McMinn, Vivian H Heyward

Abstract Traditionally, rock climbing was one aspect of Objectives-To report the physiological mountaineering. Mountaineering usually in- responses ofindoor rock climbing. volves multiday summit attempts of high Methods-Fourteen experienced climbers mountains that combines hiking, scrambling, (nine men, five women) performed three and technical climbing on rock and ice while climbing trials on an indoor climbing carrying all necessary gear in a pack. wall. Subjects performed three trials of There is now an international circuit of increasing difficulty: (a) an easy 900 verti- climbing competitions that take place on cal wall, (b) a moderately difficult nega- indoor climbing walls. Many indoor climbing tively angled wall (1060), and (c) a difficult gymnasiums have been constructed in the horizontal overhang (1510). At least 15 United States and Europe using specially minutes separated each trial. Expired air fabricated modular holds which enable climb- was collected in a Douglas bag after four ers to train regardless of the season. Climbing minutes of climbing and heart rate (HR) walls are set up to accommodate varying skill was recorded continuously using a tele- levels by modifying wall angles and hold size. metry unit. Arterialised blood samples Despite the rising popularity of this sport, to were obtained from a hyperaemised ear date there are few studies reporting physiologi- lobe at rest and one or two minutes after cal responses during rock climbing. Much of each trial for measurement of blood the research on mountaineering has focused on lactate. physiological changes at high altitude.' In Results-Significant differences were addition, some studies have measured physi- found between trials for HR, lactate, ological responses during exercise using either oxygen consumption (Vo,), and energy a Versaclimber"6 or climbing treadmill 8 to expenditure, but not for respiratory ex- simulate climbing. Although Williams et a? change ratio. Analysis of the HR and Vo, reported heart rate (HR) and plasma catechol- responses indicated that rock climbing amine responses during ascents of short rock does not elicit the traditional linear HR- faces, the angle of the ascent and difficulty of Vo, relationship characteristic of tread- the climbs were not specified. One recent study mill and cycle ergometry exercise. During by Billat et al'0 examined the change in whole http://bjsm.bmj.com/ the three trials, HR increased to 74-85% of body oxidative metabolism during climbing on predicted maximal values and energy modular walls. They used four experienced expenditure was similar to that reported climbers to compare Vo~max measured during for running at a moderate pace (8-11 min- running and upper body pulling with that utes per mile). measured while climbing two difficult climbing Conclusions-These data indicate that courses. indoor rock climbing is a good activity to Thus the purpose ofthe present study was to increase cardiorespiratory fitness and measure physiological responses to indoor rock on October 2, 2021 by guest. Protected copyright. muscular endurance. In addition, the climbing during easy, moderately difficult, and traditional HR-Vo, relationship should difficult climbs. Knowledge of metabolic and not be used in the analysis ofthis sport, or cardiovascular responses to various activities is for prescribing exercise intensity for useful for exercise prescription, to evaluate the climbing. safety of activities for various populations, to (BrJ Sports Med 1997;31:224-228) code more precisely for activity self-reports, and to assess nutritional needs and training Keywords: rock climbing; caloric expenditure; heart methods. In addition, we sought to provide a Center for Exercise rate; oxygen consumption base of descriptive measures that can be and Applied Human utilised to generate more complex physiologi- Physiology, University cal questions for the sport in future research ofNew Mexico, Rock climbing has experienced rapid growth as studies. We hypothesised that there would be Albuquerque, NM a recreational activity and an international significant differences in the HR, oxygen 87131, USA competitive sport in the past decade. Although consumption (Vo,), blood lactate, energy C M Mermier there is a lack of accurate statistics on the R A Robergs expenditure (EE), and respiratory exchange S M McMinn number of climbers, Smoot' estimated that ratio (RER) for the three levels of climbing dif- V H Heyward there may be more than 4 million in the United ficulty. States alone. Correspondence to: Much of the current growth in the sport is Dr Mermier. due to increased participation in climbing on Methods Accepted for publication short rock walls and indoor climbing, employ- Fourteen climbers (nine men, five women) 26 February 1997 ing strenuous gymnastic type movements. volunteered for the study. Subjects responded Physiological responses during rock climbing 225

to recruitment posters placed at a local indoor Expired air was collected during the last climbing facility. They were experienced climb- minute of each climbing trial using a Douglas ers who were able to complete three rock bag attached to the climbing harness. A face Br J Sports Med: first published as 10.1136/bjsm.31.3.224 on 1 September 1997. Downloaded from climbing courses of increasing difficulty taking mask (M 1410, Hans Rudolph, Kansas City, five minutes each. MO, USA) covering the nose and mouth was Volunteers reported to the climbing facility attached to 1 m of low resistance tubing with their climbing harness, shoes, and chalk connected to a 200 litre capacity Douglas bag. bag. All subjects refrained from exercising at Subjects wore this apparatus throughout each least 12 hours before testing, and eating at least climb. A two way valve was opened during the two hours before testing. Comprehensive last minute of each trial to collect expired air health history questionnaires showed that all into the Douglas bag. The valve was opened as subjects were free from injury and disease. the subject approached the lowest footholds, Informed consent was obtained from each par- and the gas sample was obtained without ticipant before testing. delaying the progress of the climber. The valve Subjects were weighed in shorts and T-shirts was closed immediately after the subject without shoes on a calibrated medical balance returned to ground. The total collection time beam scale (Health-o-meter, Bridgeview, IL, was recorded for the calculation of volume of USA) to the nearest 0.1 kg. Gear weight expired air (VE). (climbing shoes, harness, chalk bag, and data VE was measured using a flow meter (Singer, collection instrumentation) was measured on Philadelphia, PA, USA). Fractions of oxygen the same medical balance beam scale, and and carbon dioxide were measured with averaged 3.1 kg with less than 0.5 kg variation paramagnetic and infrared analysers respec- between subjects. Total weight was calculated tively (Erich Jaeger, Hoechberg, Germany), by adding gear weight to body weight (since which were calibrated with gases of known per- this is the weight that was supported during centages. Vo, Vco,, and RER were calculated climbing). Height was measured to the nearest and EE was calculated using the non-protein 0.5 cm. RER kJ equivalents. All gas samples were ana- All trials for each subject were performed on lysed within one hour of data collection. HR the same day. Before any data collection, was measured continuously and stored in subjects were allowed to practice climbing memory using a small telemetry unit (CIC while wearing the data collection apparatus. Heartwatch, Hempstead, NY, USA). The The preparatory time was also used to ensure transmitter was placed on the chest and that all apparatus was properly and securely attached to two standard electrocardiograph fitted. Before each trial, subjects performed a electrodes. Electrodes were used in place of the standardised timed five minute warm up chest strap provided by the manufacturer to including stretching and easy climbing. Sub- prevent constriction of the chest which may jects then performed three climbs of increasing have restricted breathing. The receiver was difficulty on 6.35 m walls, each lasting five attached to the subject's wrist and was angled minutes. Difficulty was increased by setting so that researchers could easily read the digital climbs on walls with steeper angles and with display to ensure that the telemetry unit was smaller and fewer handholds and footholds. functioning properly during the trials. The http://bjsm.bmj.com/ Arrangements were made with the climbing average HR from the final minute of each trial gym staff to refrain from moving any holds on was used for analysis. the three courses until the study was com- Blood samples from the ear lobe were pleted. Subjects were inactive for 15 to 20 min- obtained before the first climbing trial, and utes between each climbing trial. To ensure after each climbing trial to determine resting that a true resting baseline condition was and exercising blood lactate concentrations. achieved, succeeding trials did not begin until Before any other data collection, a topical heat- HR returned to resting pre-exercise values. ing agent (Balsem Gosok, Tangerang, Indone- on October 2, 2021 by guest. Protected copyright. The three climbs were performed in ascend- sia) was rubbed on to both ear lobes to stimu- ing order of difficulty according to the late blood flow to the area. After 15 minutes of Yosemite decimal system." The first climb was seated rest, a sterile lancet was used to make a an easy 900 vertical wall, rated 5.6. The second small incision into the base of one ear lobe, and climb was a moderately difficult negatively 30 gl arterialised blood was collected into a angled wall (1060), rated 5.9. The last climb heparinised capillary tube. The blood was then was a difficult horizontal overhang of 1510, transferred to a tube prepared with 100 pl 7% rated 5.11+. Top ropes were used for safety perchloric acid. Only one resting blood sample reasons; however, subjects climbed up and was taken to lessen the number of ear down the walls continuously without aid from punctures required. Post-exercise blood sam- any rope tension. Subjects who lost their grip ples were drawn one or two minutes after each and were forced to momentarily fall on the climbing trial to allow time for the subject to rope were allowed to continue, but were not remove the apparatus and sit down after climb- allowed to rest. Two female rock climbers were ing. Research shows that during these initial unable to finish the most difficult climb minutes of recovery, lactate concentrations are without rest. None of their data were included maximal or remain elevated for this type of in any analyses. Subjects were instructed to exercise."-4 Lactate was analysed by an climb at their normal pace but were told to enzymic spectrophotometric technique. All minimise isometric holding. There were a samples were assayed in duplicate. similar number of ascents and descents for all Each subject was hydrostatically weighed'5 at subjects (no more than two laps difference). residual volume' using standard procedures 226 Mermier, Robergs, McMinn, Heyward

Table 1 Descriptive characteristics ofrock climbers. Data are means (SD) maximal HR (220 - age). These results were

similar in range to, but different in degree of Br J Sports Med: first published as 10.1136/bjsm.31.3.224 on 1 September 1997. Downloaded from Group Age (years) Weight (kg) Height (cm) Bodyfat (%1) change across trials from, those reported by Men (n=9) 26.7 (7.8) 66.3 (6.1) 175.5 (5.6) 6.8 (2.6) Watts et at8 for five climbing trials ranging from Women (n=5) 32.4 (9.7) 54.5 (3.9) 164.7 (5.6) 14.6 (2.3) 80 to 1020 angles using a Treadwall (Brewers Combined 28.4 (8.6) 62.3 (8.3) 170.7 (8.7) 10.2 (4.6) Ledge, Jamaica Plain, MA, USA) climbing treadmill. A direct comparison between climb- within a week of the climbing trials. Body den- ing trials for these two studies is difficult since sity was converted to percentage body fat using a rating system such as the Yosemite decimal the equation of Brozek et al." system was not used by Watts et al.' However, Independent t tests were used to determine an adequate comparison can be made using whether or not there were gender differences angles of the climbing trials. In their study, the for each of the dependent variables (HR, Vo2, average HR increased from 156 beats/min (800 lactate, EE, VE, VcoV, and RER). No significant angle) to 171 beats/min (910 angle) but differences (P>0.05) were found. Therefore plateaued between 91 and 1020 (171-173 data for the men and women were pooled for beats/min). The failure of the HR to increase all subsequent analyses. One way analysis of across the last three trials could be attributed to variance with repeated measures was used to the small difference in angle between the trials. compare the HR, Vo, lactate, EE, VE, VCo,, In their study, there was an average of 60 and RER responses across the three climbing increase in angle with each successive trial. trials. Scheff& post hoc tests identified which This may not have been a large enough change means differed significantly from each other. to observe a HR difference, especially at the P<0.05 was used to define statistical signifi- steeper angles. cance. Billat et al'0 measured HR during two climbs rated 7b (French rating system), which roughly Results corresponded in difficulty to the 5.1 1 + Table 1 summarises the physical characteristics (Yosemite decimal system) trial. Average HR of the subjects. Table 2 gives the average values was 176 and 159 beats/min for the first and for HR, lactate, VE, Vco2, and EE for each second trials respectively, which corresponded climbing trial. The main effect of the trials was to an average of 85.5 and 77% of the subjects' significant for HR (F(2,26) = 37.43, P = running maximal HR measured during a 0.0001), lactate (F(3,39) = 44.242, P = treadmill test. 0.0001), VE (F(2,26) = 3.657, P = 0.0399), Regardless of angle or difficulty of climbing VCo2 (F(2,26) = 4.801, P = 0.0168), and EE trials, the results from the present study and the (F(2,26) = 3.947, P = 0.0318). ScheffM other studies8 1O show relatively high HR comparisons for HR and lactate indicated that responses during climbing exercise. This in- the average HR and post-exercise lactate for all crease in HR during rock climbing can be trials differed significantly from each other. explained in part by the use ofintermittent iso- Vo,, VE, Vco,, and lactate values for the metric muscular contractions (37% of total

difficult trial were significantly larger than for ascent duration)'0 and the reliance on the arms http://bjsm.bmj.com/ the easy trial. Also, the average resting lactate as a major muscle group during more difficult differed significantly from the post-exercise climbing trials. lactate levels for all three climbing trials. The Research has shown that isometric contrac- average EE for the easy trial (0.622 kJ/kg per tions produce a disproportionate increase in min or 38.9 kJ/min) was significantly less than HR relative to Vo2 at any level of work.'120 It that for the difficult trial (0.844 kJ/kg per min has also been shown that the magnitude of the or 52.7 kJ/min). There was no significant cardiovascular response to isometric contrac- difference for RER across the trials. tion is directly influenced by the size of the on October 2, 2021 by guest. Protected copyright. contracting muscle mass.' Another factor that may be important in the understanding of HR Discussion responses during rock climbing is arm position. HEART RATE RESPONSES During rock climbing, the arms are often held Mean HR during three climbing trials in- above the level of the heart. Astrand et at' creased to 142, 155, and 163 beats/min for the reported greater increases in lactate, HR, and easy, moderate, and difficult trials respectively. blood pressure for carpenters nailing with the The means correspond to 74-85% ofpredicted arms in a vertical position above the head com- Table 2 Comparison ofthe physiological variables for easy, moderate, and difficult pared with nailing at waist level. Although the climbing trials (n=14). Data are means (SD) position of the arms may be anywhere from level with the feet to fully extended overhead Variable Easy (5.6) Moderate (5.9) Difficult (5. 11 +) during rock climbing, much of the time the HR (beats/min) 142 (19)*t 155 (15)*t 163 (15)j# arms are above the level of the heart. Vo, (ml/kg per min) 20.7 (8.1) 21.9 (5.3) 24.9 (4.9)t Psychological stress may also be a considera- RER (CO,/02) 0.81 (0.06) 0.84 (0.09) 0.86 (0.11) EE (kJ/kg per min) 0.622 (0.393) 0.665 (0.318) 0.844 (0.309)t tion in the understanding of HR responses VE (litres/min) 32.6 (16.4) 39.8 (14.5) 44.3 (14.5)t during rock climbing. Williams et al' measured Vco, (ml/kg per min) 17.4 (6.2) 19.2 (4.8) 22.3 (4.2)t* HR and plasma catecholamine responses Lactate (mmoln) 1.64 (0.63)*t 2.40 (0.68)** 3.20 (0.97)11 during rock climbing. Subjects undertook two HR = heart rate; Vo2 = oxygen consumption; RER = respiratory exchange rate; EE = energy climbs on the same day. The first trial was car- expenditure; Vco, = carbon dioxide production. ried out after the ingestion of a placebo tablet, * P < 0.05 v difficult. and the second after [ t P < 0.05 v moderate. ingesting oxprenolol (a * P < 0.05 v easy. blocker). HR rose during both trials, with mean Physiological responses during rock climbing 227

(SD) maximum HR of 166 (20) beats/min climbing routes, as determined by video analy-

during the placebo trial, and 120 (10) beats/ sis of the four subjects on the climbing routes. Br J Sports Med: first published as 10.1136/bjsm.31.3.224 on 1 September 1997. Downloaded from min for the oxprenolol trial. Plasma catechol- Thus the disproportionate use of the smaller amine levels rose only during the placebo trial. upper body musculature combined with inter- Based on these physiological measures, the mittent isometric work during difficult climbs authors concluded that increases in HR are due may explain why Vo, did not increase in more to anxiety or fear of falling than to physi- proportion to HR during the more difficult cal exertion during difficult rock climbing on climbing trials. small cliffs. Billat et al'0 also addressed this issue by allowing their four subjects to train LACTATE RESPONSES extensively on the routes before the trials to The post-exercise lactate concentrations in- minimise psychological stress during climbing. creased significantly across the climbing trials During the present study, psychological from 1.28 mmol/l at rest to 1.64, 2.40, and stress was not measured, but is assumed to be 3.20 mmol/l for the easy, moderate, and limited somewhat by testing experienced difficult climbing trials respectively. These climbers and by the use of safety ropes during data, along with increased RER from 0.81 to climbing trials. Nevertheless, owing to the 0.86, reflect the increased physiological de- observation that some fear of heights seems to mands of the moderate and difficult climbs as be common, the comments of Williams et al compared with the easy climb, as well as an cannot be discounted. increased reliance on glycolytic metabolism as the climbing trials increased in difficulty. Vo2 RESPONSES Post-exercise lactate concentrations meas- The results ofthe present study show a marked ured during the present study were lower than increase in HR without a concomitant increase those reported for simulated climbing,8 arm in Vo2 across the trials. Vo, values were 20, 22, plus leg ergometry," overhead nailing,2' climb- and 25 ml/kg per min for the easy (5.6), mod- ing modular walls,'0 and treadmill running.7 erate (5.9), and difficult (5.11+) trials respec- Subjects reported forearm fatigue without tively. Billat et al'o reported average Vo, values concomitant leg fatigue after the moderate and of 25.9 and 20.6 ml/kg per min (46 and 37.5% difficult climbing trials. During the trials on of subjects' measured running Vomax)for two steeper terrain, most of the lactate production climbs rated 7b. Watts et al also reported low may have been in the forearm, a relatively small Vo, values compared with corresponding HR muscle mass. values during Treadwall climbing. The Vo, Given the high HR values during the three values were slightly higher (20.9-31.7 ml/kg trials, lactate concentrations were lower than per min) compared with those observed in the expected. Two possible explanations as to why present study. post-exercise lactate did not increase as ex- Data from these three studies show relatively pected during the three climbing trials are the low Vo, values compared with corresponding effects of dilution caused by the large central HR levels. These data indicate that the venous blood volume and impaired lactate

relationship between HR and Vo, appears to be clearance during isometric contraction. Uptake http://bjsm.bmj.com/ non-linear during rock climbing. Although HR of circulating lactate by non-exercising muscle increased progressively as a function of diffi- may be a factor as well. This point is addressed culty, Vo, remained constant across the trials. in a study by Richter et al4 in which lactate This response to rock climbing differs from the concentration was measured during knee typical linear HR-Vo, relationship demon- extension exercise, with and without accompa- strated for exercise modes such as running and nying arm cranking. The authors concluded cycling.7 22 that both exercising and non-exercising muscle Isometric work elicits a disproportionate rise is capable of lactate uptake and removal from on October 2, 2021 by guest. Protected copyright. in HR in relation to Vo2. Although care was the circulation. taken in the present study to instruct subjects Lower lactate concentrations were measured to minimise isometric holding during the during the present study compared with values climbing trials, isometric work could not be during Treadwall climbing and climbing on eliminated. Climbing requires combined arm high-angled artificial walls. Billat et al'0 re- and leg work, characterised by dynamic moves, ported 5.75 and 4.3 mmol/l after climbing two interspersed with periods of isometric muscu- difficult (7b) routes, lasting an average of 3.45 lar contractions. This pattern alternates be- minutes. Also, Watts et al' observed mean tween the legs and arms, usually allowing two lactate levels of 3.6 mmol/l for the lowest angle to three points of contact on the holds for sup- to 5.9 mmol/l for the steepest angle. port while moving. In general, on easier climbs, the legs do more of the work, similar to climb- ENERGY EXPENDITURE ing a ladder. However, as climbs become more In the present study, the mean EE values for difficult, the importance of arm work and the three climbing trials were 0.622,0.665, and isometric contraction increases. Although the 0.844 kJ/min per kg (38.9, 41.4, and 52.7 amount of isometric work was not measured in kJ/min) respectively, for a mean body weight of this study, it was observed that climbing speed 62.3 kg. These values reflect energy expendi- slowed and isometric holding increased with tures similar to those for running on a horizon- the difficulty of the climbing trial. tal surface at speeds of 10:30, 10:15, and 8:00 As mentioned previously, Billat et alf' noted minutes per mile respectively.25 that isometric work represented more than one Watts et al' reported average EE ranging third ofthe total climbing time for two difficult from 43.5 to 46.8 kJ/min for five climbing trials 228 Mermier, Robergs, McMinn, Heyward

the highest EE attained 1 Smoot J. Is climbing really dangerous? Rock & Ice 1993; on the Treadwall, with 58:52-8. at the 860 angle. Although they found no 2 Kramer P, Drinkwater B. Women on Annapurna. Physician Br J Sports Med: first published as 10.1136/bjsm.31.3.224 on 1 September 1997. Downloaded from significant differences in EE with increasing Sports Medicine 1980;8:93-9. 3 Oelz 0, Howald H, di Prampero PE, Hoppeler H, Claassen climbing angle, our data show the average EE RJ, Bihlmann A, et al. Physiological profile of world-class during the easy trial was significantly less than high-altitude climbers. JAppl Physiol 1986;60:1734-42. trial. Again, this disparity 4 Watts PB, Martin DM, Schmeling MH, Silta BC, Watts AG. during the difficult Exertional intensities and energy requirements of technical may be explained by differences in angle and mountaineering at moderate altitude. J Sports Med Phys difficulty of the climbing trials between the two Fitness 1990;30:365-76. 5 Ballor DL, Becque MD, Katch VL. Metabolic responses studies. The larger average difference in angles during hydraulic resistive simulated climbing. Res Q Exerc between successive trials in the present study Sport 1988;59: 165-8. why the EE increased across trials, 6 Brahler CJ, Blank SE. Versa Climbing elicits higher V02,... may explain than does treadmill or rowing ergometry. Med Sci Sports while it remained constant during the Tread- Exerc 1995;27:249-54. wall study. Although the average increase in 7 Watts PB, Drobish KM, Deaur KL, Gibbons TP, Ringheim SD, Sulentic JE. Physiological comparison between simu- RER was not significant in the present study lated rock climbing and treadmill running at the same heart across trials, there was a tendency for RER to rate. Med Sci Sports Exerc 1993;25:S81. trials increased in difficulty. 8 Watts PB, Drobish KM, Ringheim S. Physiological re- rise as the climbing sponses and energy costs of rock climbing at various diffi- culty levels. Physiologist 1992;35:233. Conclusions 9 Williams ES, Taggart P, Carruthers M. Rock climbing: observations on heart rate and plasma catecholamine con- Indoor rock climbing expends energy at a rela- centrations and the influence ofoxprenolol. BrJ Sports Med tively high rate. The increase in Vo2 for this 1978;12:125-8. walking, 10 Billat V, Palleja P, Charlaix T, Rizzardo P, Janel N. Energy activity was similar to moderate paced specificity of rock climbing and aerobic capacity in and mean HR increased to 74-85% of age pre- competitive sport rock climbers. J7 Sports Med Phys Fitness dicted maximal values. Our data indicate that 1995:35:20-4. 11 Graydon D, editor. Mountaineering: the freedom of the hills. indoor rock climbing requires moderate levels 5th ed. Seattle: The Mountaineers, 1992:430-2. of physical exertion and therefore may be a 12 Belcastro AN, Bonen A. Lactic acid removal rates during controlled and uncontrolled recovery exercise. Jf Appl Phys good activity for increasing cardiorespiratory 1975;39:932-6. fitness and muscular endurance, especially in a 13 Wahren J. Quantitative aspects of blood flow and oxygen sedentary population. uptake in the human forearm during rhythmic exercise. previously Acta Physiol Scand 1966;67:S193. Data collected during three climbing trials 14 Dodd S, Powers SK, Callender T, Brooks E. Blood lactate showed significant increases in HR and lactate disappearance at various intensities of recovery exercise. J Given that Appl. Physiol 1984;57:1462-5. but only modest increases in Vo2. 15 Bonge D, Donelly JE. Trials to criteria for hydrostatic isometric muscular contraction and raising the weighing at residual volume. Res Q Exerc Sport 1989;60: above the level of the heart are often nec- 176-9. arms 16 Motley HL. Comparison of a simple helium closed method essary during climbing, the traditional HR-Vo, with oxygen circuit method for measuring residual air. relationship should not be used in the analysis American Review of Tuberculosis and Pulmonary Disease 1957;76:601-15. ofthis sport or for prescribing exercise intensity 17 Brozek J, Grande F, Anderson JT, Keys A. Densiometric for climbing activities. Also, the significant dif- analysis ofbody composition: revision of some quantitative in HR and lactate between three assumptions. Ann NYAcad Sci 1963;110:1 13-40. ferences 18 Lind AR, Taylor SH, Humphreys PW, Kennelly BM, Don- increasingly difficult climbing trials (and sig- ald KW. The circulatory effects of sustained voluntary Sci 1964;27:229-44. nificant difference between the easy and muscle contraction. Clin http://bjsm.bmj.com/ 19 Mitchell JH, Schibye B, Payne FC III, Saltin B. Responses difficult trials for Vo,, Vco,, VE, and EE) indi- of arterial blood pressure to static exercise in relation to cate that the ratings system currently used by muscle mass, force development, and electromyographic well between easy, activity. Circ Res 1981;48:170-5. climbers discriminates 20 Seals DR, Washburn RA, Hanson PG, Painter PL, Nagle FJ. moderate, and more difficult climbs. Increased cardiovascular response to static contraction of Additional research is needed to assess the larger muscle groups. J Appl Physiol 1983;54:434-7. 21 Astrand I, Guharay A, Wahren J. Circulatory responses to amount of isometric and dynamic movement arm exercise with different arm positions. Jf Appl Physiol during climbing, the relative use of aerobic and 1968;25:528-32. for energy pro- 22 Wyndham CH. Submaximal tests for estimating maximum on October 2, 2021 by guest. Protected copyright. anaerobic metabolic pathways uptake. Can Med AssocJ7 1967;96:736-45. duction during climbing, as well as the contri- 23 Secher NH, Ruberg-Larson N, Binkhorst RA, Bonde- bution of muscle strength and endurance to Peterson F. Maximal oxygen uptake during arm cranking and combined arm plus leg exercise. J Appl Physiol rock climbing performance. 1974;36:515-18. 24 Richter EA, Kienes B . Saltin B, Christensen NJ, Savard G. invaluable Skeletal muscle glucose uptake during dynamic exercise in The authors would like to thank Craig Keaty for his muscle mass. AmJPhysiol 1988;254:E555- assistance in subject recruitment, data collection, and access to humans: role of the climbing wall facility. We would also like to thank Sharon 61. Griffin and Jim Milani for their help in preparing the 25 Passmore R, Durnin JVGA. Human energy expenditure. manuscript. Physiol Rev 1955;35:801-40.