Introduction
Muscular strength and endurance of the shoulders are essential for successful completion of many athletic and occupational tasks. Various approaches to testing both strength and endurance have been developed as a means of assessing athletic readiness (1,14,22 ), as well as occupational screening for safety and to insure adequate job compatibility (5,21,25 ). The most common test method for assessing strength is considered to be the one repetition maximum (1RM), whereas muscular endurance can be evaluated by resistance exercise repetitions or calisthenic exercises.
The 1RM technique requires the movement of a maximal weight through a full range of motion in a selected exercise. Specialized equipment and considerable familiarization training may be required to accurately assess the 1RM in various exercises. However, many occupations do not rely on maximal strength as much as they require muscular endurance . Muscular endurance is typically expressed in absolute or relative terms, with both approaches requiring the completion of as many repetitions as possible within a time limit or to muscle fatigue. The absolute endurance method uses a fixed amount of weight based on some criterion for the group being evaluated. The relative endurance method often uses a percent of the 1RM or body mass to determine the load to be lifted. Calisthenic endurance tests typically involve lifting all or part of the body mass as many times as possible within a specified time frame or to muscle fatigue in a movement that mimics a resistance exercise.
Muscular endurance lifts or calisthenic exercises have been used previously to predict 1RM strength with varying degrees of success. Whereas most investigations have focused on prediction of bench press strength from push-up performance (8,9,23 ), other exercises have received limited attention concerning the relationship between muscular endurance and strength (4,6,7,16,30 ). One of those exercises that is widely used in training programs and as measures of upper-body pulling strength is the latissimus dorsi pull-down, commonly known as a lat-pull. A specially designed machine allows the individual to sit with support across the thighs to stabilize the lower body while pulling a horizontal bar downward from an extended overhead arm position (15 ). Such a device allows the careful addition of weight to achieve the desired degree of resistance loading. The analogous calisthenic exercise to the lat-pull is the pull-up. In this exercise, the individual grips a stationary bar overhead and pulls the body mass upward to the bar. The individual is typically limited to the use of body mass as the resistance, although weight can be added via a weighted vest or belt to achieve greater resistance (15,19 ). Equipment developments have produced pull-up machines that will allow a counter-weighted reduction in body mass to achieve pull-up repetitions for those individuals unable to lift their own body mass.
Whereas several studies have reported that lat-pull repetitions can be used effectively to predict 1 RM lat-pull strength in men (3,7 ) and women (4,16 ) of diverse ages and training backgrounds, few studies have compared lat-pull and pull-up performances (3,7 ). Chandler et al. (7 ) noted that lat-pull repetitions to fatigue (RTF at 60% of 1RM) were moderately related to 1RM lat-pull (r = 0.46) but not to pull-ups (r = 0.05) in athletic men. Furthermore, unweighted pull-ups were not significantly related to 1RM lat-pull (r = −0.01). It was only when pull-up repetitions were combined with body mass that 1RM lat-pull could be predicted (r = 0.72). Considering the few studies on the lat-pull exercise, it would benefit the strength and conditioning specialist to explore the relationships among analogous shoulder pulling resistance and calisthenic exercises. Therefore, the purpose of this study was to determine the relationships of lat-pull and pull-up repetitions to both maximal lat-pull and pull-up performances in young men and women.
Methods
Experimental Approach to the Problem
The pulling motion of the shoulder musculature is a common maneuver for many individuals in industrial and athletic settings. These motions often require the individual to lift heavy loads or manipulate the body weight. Currently, there is a dearth of information in the research literature on many of these types of shoulder pulling activities. We sought to evaluate several similar shoulder pulling maneuvers to determine the relationships among them and to assess differences between the ability of men and women to perform these tasks.
Subjects
Fifty-eighty college students (35 men and 23 women) volunteered to participate after having all aspects of the study explained and giving their informed consent. Each participant had completed either a basic 12-week strength training course within the last year or had 2 years of strength training experience. In both instances, the lat-pull exercise was used as part of their program, and each subject was well versed in its performance. The study was approved by the university Institutional Review Board. Subject characteristics are given in Table 1 .
Table 1: Mean and SD for physical and performance characteristics of the participants.
One Repetition Maximum Lat-Pull Test
The 1RM lat-pull (LPmax) was performed using a seated lat-pull machine (Pro-Maxima, model FW-4; Pro-Maxima Fitness, Houston, Tex.) with support across the top of the quadriceps. Seat height was adjusted to allow the subject to start the lift with the arms fully extended. A pronated grip 30-40 cm wider than shoulder width was used throughout testing, and the horizontal bar was pulled downward in front of the head until it reached a point inferior to the chin (15,19 ). The head was maintained in a neutral position, preventing the chin from being lifted to achieve a complete repetition (Figures 1 and 2 ).
Figure 1: Starting position for the lat-pull.
Figure 2: Ending position for the lat-pull.
A warm-up using light weight and 2 submaximal sets of 5-10 repetitions at 60-70% of estimated 1RM was given before testing. After a 5-minute recovery (29 ), a weight was selected based on the judgment of the lifter and the investigator, and 1 repetition was performed. Depending on the ease of completing this repetition, 2.3 to 9.1 kg was added, and a 5-minute rest was given (29 ) before another single repetition was attempted. This procedure was followed until the subject could not lift the weight through a full range of motion. The maximum weight lifted was recorded as the LPmax, which was usually achieved in 3 to 4 attempts. The reliability of this testing method has previously been noted to range from 0.94 to 0.99 (3,4,11,20 ).
One Repetition Maximum Pull-Up Test
The 1RM pull-up (PUmax) was performed on a standard horizontal bar or a counter-weighting machine (Pro-Maxima, model PL-26) using a pronated grip 10-20 cm wider than shoulder width (19 ). If the participant could perform more than 1 pull-up repetition, resistance was added in the form of a dumbbell held between the knees. After a warm-up, the participant attempted a single pull-up with an additional weight. If the pull-up was successfully completed, a 5-minute rest was given (29 ), and another attempt was made with additional weight. This was continued until the subject was not able to lift the body mass and the weight load through the full pull-up range of motion.
If the participant was not able to complete at least one pull-up, a counter-weighing machine was used to reduce the amount of body mass lifted to achieve a complete pull-up range of motion. A 20% reduction in body mass was used for the initial lift. Depending on the ease of completion of the lift, additional counter weight was added or subtracted to achieve a single repetition. Both the weighted and counter-weighted PUmax were achieved within 3-5 attempts.
Muscular Endurance Tasks
Muscular endurance repetitions in the lat-pull (LPreps) were assessed using the same apparatus with a load equivalent to 80% of the LPmax. The subject performed the repetitions at a self-regulated pace (17 ) but was never allowed more than a 2-second pause between repetitions. The hand position was the same as used in the LPmax. The arms were extended fully during the eccentric phase of the movement, and the bar was required to be pulled to a point inferior to the chin during each concentric phase. Only those repetitions meeting these criteria were counted.
Pull-up repetitions at 80% of 1RM (PUreps) were evaluated using the same devices as for the PUmax and performed using the standard form executed from a dead hang position (19 ). The resistance for the weighted pull-ups was set at 80% of the PUmax for each participant and achieved by either adding weight to the body mass via suspending dumbbells between the knees or by counter-weighting the body mass using the counter-weighted machine. Using a pronated grip with the hands in the same position as used during the PUmax, the subject pulled upward until the inferior portion of the chin was above the bar with the head held in a neutral position. The arms were required to return to the fully extended position on each movement, and only those pull-ups where the chin reached the bar were counted. The subject was allowed to rest no more than 2 seconds between repetitions, although the pace of the exercise was not regulated (17 ). The reliability of a typical pull-up test is usually between 0.92 and 0.96 (3,4 ).
Body Composition Assessment
Body composition was assessed for each participant using the gender-specific 3-site Jackson-Pollock skinfold equations (12 ). Three measurements were taken at each site, and the average used to represent the site. The sites used were the chest, abdomen, and thigh for men and the triceps, suprailiac, and thigh for women. The sum of skinfolds was used to predict density, and predicted density was converted to %fat using the Siri equation (27 ). Lean body mass (LBM) was estimated as: body mass × (1 − %fat/100).
Statistical Analyses
Multivariate analysis of variance (MANOVA) was used to determine significant differences between sexes. Analysis of covariance (ANCOVA) was used to hold the effect of certain variables constant while observing the difference between sexes and performance variables. Pearson correlation coefficients were used to evaluate the relationships among pertinent variables within each sex. Multiple regression analysis was used to determine the independent variables and their contributions to the common variance for the best prediction of each maximal strength performance. All tests were considered at the 0.05 level.
Results
MANOVA revealed that men were significantly different from women on all variables except age and LPreps (Table 1 ). Women performed significantly more PUreps at 80% of 1RM and had a greater LPmax:PUmax ratio than men. Expressing the strength performances relative to body mass or LBM reduced the difference between the sexes but did not eliminate it. When LPmax and PUmax were expressed relative to LBM, men were 46 and 34% stronger, respectively, than women. However, if the gender differences in both LBM and %fat were held constant using ANCOVA, there was no significant different in LPmax or PUmax between men and women.
Body mass and LBM were significantly related to both LPmax and PUmax in men (Table 2 ) but only to PUmax in women (Table 3 ). Relative body fat was not significantly related to either maximal lift or maximal repetitions in either sex. However, when step-wise multiple regression was used to predict LPmax and PUmax from body composition components in men, both LBM and %fat were selected (Table 4 ). In women, however, LBM was the only significant predictor, and it was selected only in PUmax. Neither body composition component reached a significant level of inclusion for predicting LPmax. When the two samples were combined, sex as a variable (0 = women and 1 = men) was not selected as a significant factor in identifying performance in PUmax, allowing LBM (83%) and %fat (17%) to account for all of the known variance (R 2 × 100 = 92%). In LPmax, however, sex accounted for 60% of the known variance (R 2 × 100 = 83%), whereas LBM accounted for the remaining 40%.
Table 2: Correlations among physical and performance characteristics of men (n = 35).
Table 3: Correlations among physical and performance characteristics of women (n = 23).
Table 4: Multiple regression equations to predict 1-repetition maximum (RM) lat-pull and 1-RM pull-up.
When submaximal repetitions in the analogous exercise were used to estimate maximal strength performance in the other exercise, the resulting prediction equations were different between the sexes (Table 4 ). Lat-pull repetition weight (RepWt) and LPreps were better predictors of PUmax in men than in women. In LPmax, only pull-up RepWt was selected as a significant predictor, and it was better in men than in women. When the sexes were combined, only pull-up RepWt was selected as a significant variable predicting LPmax. In predicting PUmax, sex explained 16% of the known variance (R 2 × 100 = 92%), leaving lat-pull RepWt to explain 82% and LPreps to explain only 2%.
Discussion
Pull-ups are considered to be the analogous exercise to lat-pulls (19 ), and the two exercises may often be substituted for one another in resistance training or fitness testing. Previous electromyography (EMG) analysis of the pull-up has shown that the major portion of the work is accomplished by the shoulder musculature (2,24 ). The muscles active during the early phase of the movement are the teres major, upper portion of the pectoralis major, biceps brachii, infraspinatus, and latissimus dorsi (24 ). In the later phase of the movement, the latissimus dorsi, infraspinatus, and teres major are the major muscles active (24 ).
Signorile et al. (26 ) observed the muscle activity involved in a lat-pull. However, their objective was to identify the muscle activity when using four different hand positions and widths in the lat-pull. Although they concluded that the wide-grip position with the bar pulled anterior to the body elicited greater muscle activation, no identification of the relative amounts and sequencing of motor activity in the major muscles involved was provided. Lehman et al. (18 ) noted that the lat-pull activated the latissimus dorsi to a greater degree than the middle trapzius, rhomboids, and biceps brachii. It seems obvious that an EMG study comparing the lat-pull and pull-up needs to be done to identify similarities and differences in muscle activation and sequencing. In addition, there may be biomechanical differences with regard to line of pull that could influence mechanical advantage and muscle activation.
Ricci et al. (24 ) questioned the use of pull-ups as a test for shoulder extension strength, citing the dependence on moving the total body mass to achieve success as a major problem. Four men (11%) and all 23 women in the current study were unable to perform one unweighted pull-up. Despite being unable to perform one pull-up, the 4 men had considerable variation in absolute (72.7 to 109.1 kg) and relative (0.58 to 0.75 kg·kg−1 ) 1RM lat-pull. In the remaining 29 men, 16 (46%) had relative lat-pull values <1.00 kg·kg−1 body mass (range = 0.67-0.99), yet were capable of performing at least one pull-up. Because of the limits imposed by body composition on pull-ups, submaximal lat-pull repetitions may provide a wider variation in performance and give a better indication of the functional capacity of the shoulder musculature. This might have significant implications in industrial/occupational performance screening where shoulder strength, endurance, or both are required (1,5,10,21 ).
The results of the current study agreed, in part, with the findings of Ball (3 ) concerning the use of PUreps to estimate LPmax. The correlation between PUreps and LPmax in Ball's mixed-gender sample was significantly different (r = 0.40) from the current results (r = −0.51). Even if sex was partialled out of our relationship between LPmax and PUreps, the correlation remained negative (r = −0.14; p > 0.05). Ball (3 ) noted that whereas the addition of arm length and arm circumference to pull-up performance improved the prediction of LPmax (R = 0.72), the additional anthropometric measurements required for his equation made it no more practical than performing the actual measurement of LPmax. In the current study, the accuracy of the pull-up prediction equations to estimate LPmax was increased by incorporating LBM only in men (Table 4 ). Because the estimate of LBM would typically require the measurement of several skinfolds and the derivation of LBM from predicted %fat, we concur with Ball (3 ) that this may offer no advantage over the simple measurement of LPmax. Yet we cannot exclude the idea that significant differences in upper-body musculature could play a major part in performance difference in both men and women in pulling exercises.
Vanderburgh and Edmonds (28 ) suggested that unweighted pull-ups in men were more a function of relative body fat content than a function of LBM. Because our pull-ups were performed with 80% of 1RM, it is not possible to make direct comparisons with their study. However, in our men, LBM contributed 91% to the known variance in PUmax, whereas %fat contributed only 9%. Ironically, in our women, who had over twice as much relative body fat, LBM was the only body composition element to make a significant contribution to the prediction of PUmax. In the combined sample, LBM still contributed over 82% to the known variance in PUmax prediction. Interestingly, a gender code (1 = men; 0 = women) had to be added to the regression analysis to allow any body composition elements to be selected to predict LPmax. The gender code accounted for 60% of the known variance in LPmax performance, relegating the contribution from LBM to 40%. Obviously, what would assist in solving these discrepancies would be an isolated measurement of upper-body musculature because it is known that women have a smaller proportion of their total muscle mass located in the upper body (13 ). Estimations of upper-body musculature might also go a long way in explaining the variability among men in upper-body strength and muscular endurance exercise performance.
Practical Applications
Men and women use a variety of upper-body exercises in their resistance training programs. Among these exercises, the lat-pull and the pull-up have received only limited attention in the scientific literature. Whereas the two exercises seem similar in their motion, this study provides sufficient documentation of differences in the factors contributing to their performance to indicate that they should not be used interchangeably.
This is one of the first studies to use the counter-weighting pull-up device to assess differences between men and women in muscle strength and endurance performance. Because body composition and the distribution of muscle mass in the body seem to play prominent roles in the performance of these exercises, the counter-weighting devices can make a major contribution by allowing those individuals with limited upper-body pulling strength to increase their training potential. When training loads are set relative to 1RM values, it seems that women can perform pull-up repetitions at the same level as men. Using a counter-weighted pulling device might be especially advantageous for women because our results indicate the pull-up is not analogous to the lat-pull, and thus, each exercise may be providing a unique training stimulus to the muscle groups used in their performance.
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