The reason(s) for deficiencies in scaling models likely occur because the exact relationship between anthropometrics, body mass, muscle mass distribution and maximum strength has not been completely determined (10,11,15,30). Furthermore, weightlifting is not a pure strength sport but is influenced by technique factors (14,25), and may be better characterized as a strength–speed sport in which the ability to produce a very high peak power is the major factor determining success (13,15). In any case, it is clear that maximum strength (or peak power) and weightlifting performance among athletes with widely varying body masses is not a linear function (9,15).
In an attempt to ascertain the relationship between maximum strength and weightlifting ability independent of body mass/size influences, various scaling models have been developed 5,9,18,22,30, including: body mass and lean body mass scaling (i.e., load · kg−1 or load · lbm−1), allometric scaling (i.e., the two-thirds power law: load · (body mass0.67)−1), scaling by height (load · (height)2.16)−1, and the Sinclair Formula, a polynomial equation updated every 4 yr (22). Currently, the Sinclair formula is the scaling method that has been adopted internationally for comparing performances in weightlifting (22).
Although none of the scaling methods completely consider all aspects of body dimensions such as segment lengths or muscle distribution (5,10,11,15,30), collective use of these methods may allow insights into the relationship of maximum strength to weightlifting performance. The primary purpose of the investigations presented in this paper is to characterize the relationship(s) between estimates of dynamic or isometric maximum strength and weightlifting performance. To characterize these relationships, absolute values, load · (Ht2.16)−1, and four common body mass scaling methods were used, load · kg−1, load divided by kg of lean body mass (load · lbm−1), allometric scaling (load · (body mass 0.67)−1), and the Sinclair formula. A secondary purpose of this paper is to compare high-level men and women weightlifters on these variables.
To initiate the determination of relationships between maximum strength to weightlifting performance two observations were carried out at the Olympic Training Center in Colorado Springs, CO. In the first observation the relationship of dynamic maximum strength (one-repetition maxium (1RM) squat) was studied. In the second observation isometric maximum strength (midthigh pull) was studied. All athletes were informed of the information gathering/testing procedures and all athletes signed standard testing consent forms. These studies were conducted as part of service projects in conjunction with U.S. Weightlifting and the U.S. Olympic Committee; all athletes (and parents of juniors) attending the U.S. Olympic Training Centers provided consent for testing as part of their participation in sport at the Olympic Training Centers.
The subjects were 65 national and international level men and women weightlifters. The athletes were the men's (N = 7) and women's (N = 10) resident weightlifters at the Olympic Training Center in Colorado Springs, and members of the national men's (N = 32) and women's (N = 16) junior national squads. Ages ranged from 15 to 30 yr, and body mass ranged from 46.8 to 168.7 kg (Table 1). Junior lifters were attending 2-wk training camps at the Colorado Springs Olympic Training Center, during which the weightlifters filled out questionnaires concerning their weightlifting performance capabilities.
As in most practical sports settings, actual measurement of sport performance is not always possible, due to unwelcome disruptions to training, etc. The athletes lifting capabilities at the time of the camp were assessed by questionnaire–-each athlete was asked to report his or her current capabilities in the 1RM squat (SQ), snatch (SN), and clean and jerk (C&J). It is reasonable to assume that the listed 1RM were valid representations because the lifters were all quite experienced and the U.S. national coaches and junior camp coaches checked the listed values (6). Furthermore, all of the junior lifters had competed within 3 wk of attending the camps. Previous experience by the investigators with well-trained weightlifters (N = 11), in which the 1RM (SQ, SN, C&J) were actually measured and compared with estimates, showed that the estimates were within ±5 kg of the actual value.
Correlations were calculated using Pearson's r. Differences between men and women were calculated using a t-test with a Bonferroni adjustment to account for the multiple variable comparisons (a new view of statistics, Internet Society for Sport Science, http://www.sportsci.org/resource/stats/). The criterion for statistical significance was set at P ≤ 0.05.
The subjects were American weightlifters (N = 16; 9 males, 7 females; 23.1 ± 4.2 yr; height = 166.9 ± 7.3 cm; mass = 82.9 ± 19.4 kg; body composition (%fat) = 16 ± 6). All 16 weightlifters had international weightlifting experience, and all 16 qualified for the 2004 Olympic trials and were considered elite-level American weightlifters.
All athletes had been previously familiarized with the testing procedure. Midthigh pulls were executed following a warm-up and further practice with the testing protocol and apparatus. Athletes addressed the bar while standing on the force platform within a custom-designed power rack. Athletes were placed in a midthigh pull position based on their standing posture and the estimated optimal position of their body at the initiation of the second pull in a clean. The athlete's knee angle and the bar height were record ed. Athletes performed three trials of each pull. The first trial was used to further familiarize the athletes with the procedure, as a further warm-up, and to check posture. The first trial was executed at less than the athlete's maximal ability. Trials 2 and 3 were performed as “hard and fast as possible.” Athletes' hands were attached to the bar using standard athletic tape to prevent their hands from slipping and to ensure that athletes could perform a maximal pull in spite of hand strength not being capable of exceeding their overall pull force. Midthigh pull isometric force (IPF) was measured using a large a 61 × 121.9 cm force plate (Advanced Mechanical Technologies, Newton, MA), and sampling at 600 Hz with customized Labview software (National Instruments Co., Austin, TX). Pulls were performed (Fig. 1) within a specially designed adjustable power rack (24). This procedure generates an isometric force–time curve from which isometric peak force (IPF) can be measured (Fig. 2). The peak force value was obtained from the force–time curve stored in the computer. Previous work (several hundred trials) with this system has consistently resulted in a test-retest reliability for IPF of ICCalpha ≥ 0.99.
Body mass was measured on a digital scale (Toledo International Inc., Columbus, OH). Skinfolds (SF) were measured with Lange SF calipers (QuickMedical, Snoqualmie, WA). A seven-site SF protocol was used to determine approximate body fat percentages (14). Experienced laboratory personnel measured all SF on the right side. In our laboratory, test-retest reliability for SF has been ICCalpha > 0.90.
Data were collected 1.5 wk before the U.S. National Weightlifting Championships in 2003. The best SN, C&J, and total performed at the national championships were used in the data analyses.
Relationships (Pearson r) were compared using nonnormalized/scaled and normalized/scaled values and the Sinclair formula. Due to the small number of subjects only the combined group (men plus women, N = 16) was used in the correlation analyses. Differences between men and women were calculated using a t-test with a Bonferroni adjustment to account for the multiple variable comparisons. The criterion for statistical significance was set at P ≤ 0.05.
The physical and performance characteristics of the 65 male and female weightlifters are shown in Tables 1 and Table 2. Men's values were statistically greater than women for all values except body mass (P ≤ 0.05). Correlations between selected biometric variables are presented in Table 3. Correlations between selected absolute and scaled performance variables are presented in Table 4. Correlations indicate that dynamic maximum strength, as calculated from 1RM SQ estimates, was strongly related to weightlifting performance among these weightlifters. Furthermore, it should be noted that the correlations between measures of maximum strength and weightlifting variables were generally lower for women than for men (Table 3). Sample plots for correlations are shown in Figures 3–5.
Physical and performance characteristics, for the 14 men and women weightlifters, are shown in Tables 5 and 6. Men's values were statistically greater than women for all values except body mass, IPF · kg−1, IPF · lbm−1 and IPFa (P ≤ 0.05). Correlations between IPF and weightlifting performance are shown in Table 7. Sample plots for correlations are shown in Figures 6 and 7. Observation 1 and 2: ratios of strength values of women to men (W:M) are presented in Table 8.
Maximum strength appears to be a major factor influencing the performance of a variety of sports (23), especially sports involving high force production and high-power outputs such as throwing (26) and track cycling (27). Although it is obvious that weightlifters are quite strong, the exact relationship between maximum strength and weightlifting performance has not been completely clear. It has been the authors' observation, as well as that of other authors (1,2), that among coaches and sports scientists, the degree to which various aspects of training, such as strength and technique, should be emphasized during training has been the subject of debate.
Strength can be defined as “the ability to produce force,” and can be measured isometrically or dynamically (23). The potential for strength to influence weightlifting (or other sports) performance can be conceptualized by considering the relationship of force production to acceleration and power output. Force is directly related to the ability to accelerate an object (F = ma) and to the power that can be produced (P = F · V). Furthermore, evidence suggests that maximum strength is strongly related to the ability to produce average and peak power across a wide spectrum of loads in various types of upper- and lower-body movements (6,7,20,24). Considering that peak power production is apparently the major contributing factor for performance success among elite weightlifters (13,15) and force production is a major contributor to peak power, then maximum strength would be expected to be a major factor influencing weightlifting success. Although body mass/size obviously affect strength and weightlifting performance (Table 3), it is not well understood as to the degree of influence.
Using body mass or lean body mass as a method (load · kg−1; load · lbm−1) of attempting to correct for strength differences is still widely used. However, a simple comparison based on body mass strongly biases strength and weightlifting performance measures toward the lighter athletes (10,11). Such an approach does not consider differences in biomechanics/anthropometrics or geometric similarity, and may be the weakest of the scaling methods (10,11,17,30). In the present study, correlations between variables scaled by body mass and lean body mass in observation 1 and observation 2 did not agree (Tables 4 and 7). The very strong relationships noted in observation 1 may have resulted from the heterogeneity of the subjects, whereas in observation 2, which had a smaller N, the subjects were more highly trained and showed a smaller range of strength measures.
In 1956, Lietzke (17) noted the weakness of body mass scaling and indicated that weightlifting world records were approximately proportional to the load divided by the body mass of the weightlifters to the two-thirds power (i.e., the two-thirds power law: load · (body mass 0.67)−1). The theoretical underpinnings for the two-thirds law centers on the principle of “geometric similarity,” which suggests that strength measures (S; a two-dimensional factor), and mass (M; a three-dimensional factor) conform to the relationship: S · (M 2/3)−1 (18,30). However, this method of comparison was also subsequently shown to have deficiencies. In particular, attempts to obviate differences in size based on the two-thirds law apparently will bias results towards small and particularly middle-sized athletes, such that these athletes have disproportionately large strength values (5,10,11,15). In the present study the two observations (Tables 4 and 7) produced strong to very strong correlations between allometrically scaled measures of strength.
Another recently developed scaling model for weightlifting uses the relationship between height and muscle cross-sectional area (9). This method is based on two important assumptions: 1) That elite weightlifters have achieved maximum or near-maximum muscle fiber size (i.e., cross section), then maximum strength will be directly related to the number of muscle fibers in parallel (9); and 2) Because final muscle fiber number and bone length appear to be determined as a result of commonly shared maturation factors (29), then the final number of muscle fibers should be strongly correlated with height. Thus, height among elite weightlifters should reflect muscle cross-sectional area, which in turn is strongly related to maximum strength. Again, assuming that maximum strength is a primary prerequisite for superior weightlifting performance, it should be expected that height should correlate strongly with performance. Using these basic assumptions, Ford et al. (9) found, among world champion men and women weightlifters (1993–1997), that the total weight lifted (total = SN + C&J) divided by height2.16 (load · (Ht2.16)−1) was nearly constant across body weights for both men and women. Thus, load · (Ht2.16)−1 may be a viable method of obviating body mass differences among weightlifters. However, the sample population in observation 1 contained a number of junior weightlifters that likely did not meet the assumptions for using this scaling method. Nevertheless, strong and very strong relationships were noted among strength variables scaled in this manner in both observations (Tables 4 and 7).
Realizing the deficiencies in previous scaling models, a number of different formulas for comparison of athletes of different body masses have been developed for both powerlifting and weightlifting using regression analyses (10,11,15). Although not addressing all aspects of obviating body mass when comparing strength levels (15), the Sinclair formula appears to have a reasonable theoretical underpinning; it is updated every 4 yr, and is currently the scaling method used internationally for comparing performances in weightlifting (22). As with allometric and scaling by height2.16 the very strong relationships (Tables 4 and 7) among strength variables scaled using the Sinclair formula indicate the relative importance of maximum strength independent of body mass/size differences.
Although generally strong, the correlations between measures of maximum strength and weightlifting performance are lower for women than men. This suggests that the women's performance may be relatively more dependent upon other factors such as, flexibility, technique, or speed under the bar. Furthermore, data indicate that men are stronger than women even when accounting for body mass/size differences.
Comparisons of total body measures of maximum strength among untrained men and women (8,16,19,21) indicate that the average strength ratio (women:men) is approximately 64%. This value is a summary of different methods and modes of testing (i.e., isometric vs freely moving, machines vs free weights, eccentric vs concentric). Thus, some differences may be observed when different testing devices are used. Attempts at obviating size differences by normalizing by body mass or lean body mass reduces the differences between men and women (8,28)–-a finding similar to that of the present data (Table 8).
There is little doubt that body mass influences maximum strength and weightlifting performance. However, the results of the present observations indicate that, when collectively considering scaling methods (load · kg−1, load · lbm−1, allometric, load · (Ht2.16)−1, and Sinclair formula), maximum strength is strongly related to weightlifting performance independent of body mass/size differences. This conclusion is based upon the assumption that scaling methods, at least to a large extent, obviate the effects of body mass/size. However, it is obvious that more research in this area is necessary. Furthermore, these data suggest that maximum strength may not have exactly the same influence on performance among women weightlifters compared with men.
Collectively these data indicate that maximum strength is a major contributor to weightlifting success. Although technique training is invaluable during the developmental stages of training (3), continuing to prioritize technique training as an athlete advances toward the elite level may be counterproductive. As with other strength–power techniques, it is apparent that weightlifting technique becomes stable after a few years of training (1)–-however, other contributing characteristics such as flexibility, strength–endurance, power, and maximum strength can be trained and improved for many years after technique stabilizes (2). Therefore, as a weightlifter progresses, we would argue that more training time should be devoted to strength training (and other characteristics) rather than technique. This does not mean, necessarily, that technique training should be abandoned. However, these data suggest that extensive technique training should be reduced, so that sufficient training time can be devoted to the further development of characteristics, including maximum strength, that are more likely to influence performance in a positive manner. (4,12)
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