The aim of this study was essentially applicative in the area of fitness training. Physical activity has been proved to be the most effective factor in preventing health risks due to sedentary lifestyle and in maintaining fitness; trainers and athletes are very interested in establishing whether the type and intensity of sport practiced are sufficient to fulfill this task, and this study was designed to answer to these questions. Our interest is focused on individuals who like climbing, notwithstanding fitness level or skill. The main hypothesis is that climbing exercise is per se sufficient to maintain health when the level of work per session is regularly and frequently practiced. Hence, the study was designed in order to test this hypothesis and, in that case, to establish frequency and intensity of the load that match the prescription of International Standards of Sport Sciences.
Rock climbing (RC), a variation of mountaineering, is a relatively new sport. Athletes approach the rock face via a brief route, avoiding long trekking. Top-level competitive athletes, taking advantage of modern climbing techniques, approach ascent via extremely difficult rock face, thus achieving spectacular performances. In this sport, both natural rock terrain and artificial indoor walls have been adopted. Each climb, whether on natural or artificial terrain, is classified according to the technical difficulty of the ascent. In this research, the French scale has been adopted (19).
Many authors have evaluated the physiological profile of elite RC athletes. In this profile, using measuring parameters, Watts (19) and Sheel (15) have taken into consideration various aspects, including handgrip strength, body fat (10), flexibility, skill (20), and aerobic fitness (21). Indeed, Watts reported a o2peak value of 55 mL·kg−1·min−1, which is much lower compared with the values shown in endurance athletes such as runners or cross-country skiers (1,20). Oxygen consumption during RC (o2RC), assessed primarily in indoor structures (2,11,16,17,20,21), has been reported as being between 24 and 27 mL·kg−1·min−1. Only in 1 study was o2RC measured in outdoor rock faces, and energy expenditure in outdoor activity was found to be greater than that in indoor activity, being approximately 35 mL·kg−1·min−1 (3,14).
The vast majority of these studies focus on elite athletes who take part in competitions. Few data are available on recreational noncompetitive climbers (13,14). Since this sport is gaining popularity, especially as an outdoor activity, it appeared worthwhile to study recreational climbers. The rock face we adopted for this research was deliberately chosen for its low level of difficulty, which allows ascent even for a person with little climbing experience.
The present study has been carried out with noncompetitive climbers in order to (a) assess the physiological aerobic profile; (b) compare the aerobic capability, measured by means of laboratory incremental tests, with the energy cost due to actual RC; and (c) establish, measuring heart rate (HR) and o2, whether outdoor exercise fulfills sport medicine recommendations, as reported in the American College of Sports Medicine (ACSM) guidelines (1); and (d) to define the weekly workload for maintaining a good level of cardiorespiratory fitness.
Experimental Approach to the Problem
Subjects were recruited from a group of individuals who enjoy recreational RC, mostly on the weekend. In order to assess whether RC would meet sports medicine recommendations, the physiological profiles of these noncompetitive climbers and their energy expenditure during RC activity on a natural rock face were evaluated. The physiological profile was assessed by metabolic measurements in the laboratory using a modern metabolimeter and stressing the subjects with a maximal exhaustion test on the cycloergometer. These same physiological parameters were assessed in an outdoor environment using a metabolimeter, allowing telemetric communication between the subject and researcher. Moreover, a blood sample for lactate assessment was collected after exercise to evaluate the metabolic substratum required.
Following approval of the local ethics committee, 13 noncompetitive climbers (8 men and 5 women) agreed to take part in the study. All subjects were experienced climbers; they were able to climb rock faces classified as 7a for men and 5b for women according to the French scale (18); furthermore, they had about 10 years of climbing activity, and, in most cases, this was the only sport practiced regularly. All subjects signed the informed consent form and all were requested to complete a questionnaire regarding his or her usual RC activity. No training other than RC or mountaineering had been performed during the 6 months prior to the study. Before beginning the study, 4 plicometry measurements were made (bicipital, tricipital, subscapular, and suprailiac) and the percentage of body fat was estimated according to Durnin and Womersley (6). Age and mean values of anthropometric measurements are reported in Table 1.
Oxygen consumption, carbon dioxide output, pulmonary ventilation, and HR were assessed using a breath-by-breath gas analyzer (Quark b2; Cosmed, Pavona, Rome, Italy). Furthermore, ECG was monitored (Delta 612; Cardioline, Milan, Italy). A cycle ergometer (E 200; Ergoline, Bitz, Germany) was used to perform incremental tests and the following protocol was adopted: after warm-up (3 minutes) at 40 W, the load was increased by 10 W every 15 seconds until exhaustion. At least 2 of the following 3 conditions were considered as indicative of exhaustion: o2 did not increase further while power continued to increase, the respiratory exchange ratio was >1.15, 95% of theoretical maximal HR was reached. The o2 at exhaustion represents the maximal (o2peak). Pulmonary ventilation, o2, and carbon dioxide output measurements were also adopted to estimate the anaerobic threshold (VT), according to Wasserman et al. (18) findings.
Outdoor measurements were performed on a natural rock face 25 m high, graded as 4a on French scale, corresponding to 5.7 level on the Yosemite Decimal System, 5th level on the Union Internationale des Associations d'Alpinisme, 15th level of Australian and New Zealand System, and 4c level on the United Kingdom System. This face is commonly used for basic training by our rock climbers; all participants were able to achieve continuous ascent without hold phases. Subjects were invited to climb at a comfortable speed (the speed that each subject spontaneously adopted). All parameters assessed in the laboratory were also evaluated both during the climbing and recovery phase (i.e., return to o2 rest values) using a portable gas analyzer (K4RQ, Cosmed); data were collected every 15 seconds (Figure 1).
A o2 rest level was measured with the subject maintaining an orthostatic posture for 5 minutes before testing. Blood lactate was assessed using a portable lactacidimeter (Lactate Pro; Arkray, Kyoto, Japan) on capillary blood collected from the ear lobe, and the measurements were made at the top of the rock face with the subject in an erect posture, 3 and 5 minutes after the end of the climb. Oxygen consumption during RC (o2RC) was computed by subtracting the o2 rest level from o2. The total caloric expenditure (cal·kg−1) was calculated from the o2 measured during the ascent and recovery times, using the following formula: (o2−o2 rest level) × 5.05 × (ascent time + recovery time).
It is worthwhile pointing out that the 2 metabolimeters used in the laboratory and outdoors were almost identical (i.e., the same hardware for gas measurement and the same software to calculate data); the only difference concerned the teletransmission of data. The accuracy and reliability of the metabolimeters used were ascertained by Meyer and colleagues (12).
Data are expressed as mean ± SD. An impaired t-test was used to compare data on the men and women in the statistical analyses of results. Variance homogeneity was verified by the Levene test. The level of statistical significance for the Levene test and t-test was set at P ≤ 0.05.
Physiological Profile Assessed by Laboratory Tests
Mean o2, VT values, and maximum HR (HRpeak) for men and women are shown in Table 2; VT, expressed as a percentage of o2peak, is also reported. The differences between men and women were not statistically significant.
Rock Face Data
The o2 values measured during climbing showed the same general trend in all subjects. Three phases were identified: in the initial phase, o2 increased sharply (phase 1) and then leveled out in the final 2 minutes (phase 2); during the recovery period, o2 decreased toward the resting values (phase 3). The last 2 minutes of the exercise were assumed to be indicative of o2RC steady state. The o2 trend during climbing minus the rest value for a representative male subject is shown in Figure 2.
The o2RC, HRRC, peak blood lactate, and total caloric expenditure values are shown in Table 3. Since each subject was encouraged to climb at his or her comfortable speed, the ascent time resulted largely varied between subjects (288 ± 133 seconds). Total oxygen consumption-and consequently the energy expenditure-results directly correlated with the time spent in ascending the face (R = 0.92). Conversely, o2RC resulted as absolutely independent (R = 0.04) from ascent time.
In order to identify the type of metabolism involved in RC, the level of aerobic exercise was calculated comparing rock face data with laboratory measurements: o2RC metabolic expenditure, expressed as a percentage of o2, was 70 ± 6% in men and 72 ± 8% in women; HRRC, expressed as a percentage of HRpeak, was 83 ± 8% in men and 90 ± 5% in women.
The aerobic fitness in the climbers taking part in the study was poor if compared with elite endurance athletes. Indeed, Cerretelli et al. (5) reported a mean o2peak of 75 mL·kg−1·min−1 in cyclists, long distance runners, and skiers of both genders. Our data, when compared with the literature, classify noncompetitive climbers as sedentary subjects (5). Nevertheless, noncompetitive rock climbers are endowed with a level of cardiorespiratory fitness convenient for maintaining health conditions, according to the recommendations proposed by the ACSM (1), as discussed below. Furthermore, the on-field activity completely fulfill the ACSM recommendations for maintaining health, as described in the rock climbing exercise section below.
In the present investigation, the percentage of body fat, evaluated according to the indications published by ACSM (1), can be classified as superior for the men (11.8 ± 0.95% of body mass) and excellent for women (14.3 ± 4.34% of body mass) in this study. o2peak and VT, evaluated according to ACSM (1), would be classified as excellent in the men and superior in the women in this study. Indeed, male and female climbers showed a o2peak values equal to 39.1 ± 4.3 mL·kg−1·min−1 and 39.7 ± 5 mL·kg−1·min−1, respectively. Since these values have been obtained using a cycloergometer, the correction proposed by Carter et al. (4) was applied to compare our data with the ACSM standards, which refer to a treadmill ergometer. Applying this correction, o2peak becomes approximately 45 mL·kg−1·min−1 in both genders on the treadmill. These values correspond to the 85th percentile of normal healthy male subjects, aged 40-49 years, and to the 95th percentile of normal healthy female subjects, aged 30-39 years (1). This ranking corresponds to subjects with good aerobic fitness and is in agreement with the hypothesis that RC is a valid exercise to counteract hypokinetic disease.
Improvement in upper limb strength and endurance induced by RC is reported in literature (10). Wall et al. (17) demonstrated that muscular parameters are very important to predict climbing capability. Recently, Rodio et al. (13) reported hand strength and endurance greater in RC novices than athletes in other sports.
During climbing, the o2 values correspond to 70 ± 6% and 72 ± 8% of o2peak (men and women, respectively), and these percentages are below those of the VT as evaluated in the laboratory. Moreover, the lactate peak measured at the end of the exercise confirmed that RC is a mainly an aerobic exercise (7). As far as cardiorespiratory fitness is concerned, the intensity of the exercise is well within the range recommended by the ACSM (1), as well as in the range proposed by McArdle et al. (9) and Kindermann et al. (8), to improve endurance fitness. o2RC was approximately 28 mL·kg−1·min−1 in both genders, corresponding to 8 MET, this latter value being comparable to those obtained in cycling, jogging, and swimming activities (1).
Furthermore, according to the Karvonen method, reported in ACSM's Guidelines (1), the target HR required to maintain cardiorespiratory fitness should be between 124 and 157 b·min−1. Values obtained during RC are in accordance with this recommendation.
The rock face selected for this study is a typical route used by noncompetitive climbers during training because it requires a low level of climbing skill. It is noteworthy that, while total energy expense was dependent on the time spent in the face, the o2RC was independent of any other considered variable. The fact that o2 was maintained below the value 1 of lactate accumulation is related to the ascent speed.
The time spent by the climbers in each session and the frequency of sessions per week were calculated based on the information provided by the climbers in an ad hoc questionnaire. It resulted that noncompetitive climbers only usually practice during the weekend and a typical session lasts about 3 hours per day. In the present study, the exercise, including recovery, lasted about 9 minutes (7 ± 2 minutes in men and 11 ± 3 minutes in women), and, typically, the exercise is repeated 10-15 times per day, for an equivalent of 20-30 times per week. Therefore, the total caloric expenditure is approximately 1000 and 1500 kcal per week in men and women, respectively, which is comparable to the caloric expenditure reported by Rodio et al. (14) for expert rock climbers and consistent with the suggestions of the ACSM to maintain aerobic fitness (1).
The HR findings observed during RC deserve some consideration. A high HR, disproportional with o2 values, has been reported to occur during RC (2,3,11,15). Sheel et al. (16) found that HR values obtained during hard RC were 89% of the HRpeak measured in the laboratory, and the o2 during RC accounted for 67% of the o2. These authors assume that the disproportional increase in HR observed during RC is due to the frequent isometric contractions of the arm muscles and the position of the hands above the head. Our findings, despite measurements having been performed on noncompetitive athletes, are consistent with these reports: HR during RC expressed as a percentage of HRpeak was 83 ± 8% in men and 90 ± 5% in women, while o2, expressed as a percentage of o2peak, was, respectively, 70 ± 6% and 72 ± 8%. The fact that women presented a significantly different increase in HR compared to the men could be due in part to the fact that the duration of exercise is longer in women.
It is worthwhile pointing out that the rock face where the study was performed is beneath their capability. This would appear to suggest that possibly a more difficult climb could demand a lower percentage of o2RC, with respect o2peak, because the holding phases may be distributed throughout the climb. In fact, the conditioning effect of climbing seems more dependent on the vertical displacement than the speed of the climb (21). This fact is confirmed by the results obtained in women, who were graded lower than men and had much lower vertical velocity (vertical displacement/climbing time); nevertheless, the o2RC was similar to that in men and the total caloric expenditure was doubled with respect to men.
The above statement demonstrated that RC, even when practiced without special experience or skill, is sufficient per se to maintain health and physical fitness. Thus, the basic hypothesis of our study was verified. For a trainer, the important information to retain is the following: (a) The difficulty of the rock face is not an essential parameter to be taken into account for health maintenance training. The rock face grade must be within the level of expertise to be climbed at a personal comfortable speed, avoiding any rapid movements that could compromise the climber's safety. (b) Exercise intensity can be judged through the HR, which must be maintained at about 80% of the theoretical maximum, estimated as 220 b·min−1 minus age in years. (c) The most important parameter is the time spent on the rock face. According to our data, the caloric expenditure for 1 minute is about 9.8 kcal for an individual of 70 kg body weight. To match the ACSM recommendation, the ascent time should be about 150 minutes per week. (d) In order to obtain a positive cardiorespiratory effect, it is necessary to practice RC on routes of an equivalent vertical displacement of 500-750 m per week. Obviously a part of this recommendation can be substituted by any other aerobic training such as swimming, running, and cycling; indeed, RC is 8 MET and this value is comparable to swimming, running, and cycling energy expenditure (1). It is noteworthy that these conclusions are equally applicable to men and women.
The authors are grateful to Marco Geri for assistance during outdoor measurements and to “Comune di Caprile” (Italy) for logistic support. The authors have no conflict of interest in connection with this paper. The corresponding author had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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