Resistance exercise is mostly performed by combining multijoint exercises with constant external resistance (isotonic) in the form of dumbbells, barbells, or machines. Scientific examination of these activities is more complicated than studying isometric exercises (meaning the body does not move) because the movement kinetics continually change in response to adjustments in body joint angles (2,15,20 2,15,20 2,15,20). For example, maximal force and torque constantly change during the deadlift exercise as the lifter moves from the starting (barbell on the floor) to the finish position (hips fully extended) (2,15 2,15). This explains why force production during a dynamic isotonic exercise is at its greatest during the portion of the movement that places the body in optimal positions and joint angle (2,29,32 2,29,32 2,29,32). In other words, a person's one repetition maximum (1RM) is limited by their maximal strength in their weakest position. This also suggests that muscles in advantageous positions are not maximally challenged during a 1RM exercise.
Recent work has examined training devices that are designed to match the changing mechanical and inertial characteristics associated with isotonic resistance (23) by providing some form of variable resistance (e.g., heavy elastic bands (1,3,9,18,23,28,30 1,3,9,18,23,28,30 1,3,9,18,23,28,30 1,3,9,18,23,28,30 1,3,9,18,23,28,30 1,3,9,18,23,28,30 1,3,9,18,23,28,30) or chains (9,18,25 9,18,25 9,18,25)). In the case of bands, 1 end is usually attached to a barbell, whereas the other end is anchored to the floor or some other stationary site. The band then stretches as the exerciser lifts the barbell away from the fixed location. The amount of stretch, and thus the resistance, increases as the exercise progresses toward the lifter's strongest position (usually the apex). Unlike isotonic resistance, the bands/chains theoretically match the increase in mechanical advantage (which occurs because of the change in body/joint position) with an increase in resistance. This variable resistance (i.e., bands) strategy should therefore address the limitations of isotonic exercise by allowing greater loading at body positions of greater mechanical advantage. Not surprisingly, coaches aware of this concept typically use variable resistance to supplement isotonic resistance during multijoint movements such as the bench press, back squat, and deadlift (2,24,31 2,24,31 2,24,31).
Scientific support of variable resistance training using heavy elastic bands is limited, with most studies focusing on the back squat (1,9,13,17,21,25,30 1,9,13,17,21,25,30 1,9,13,17,21,25,30 1,9,13,17,21,25,30 1,9,13,17,21,25,30 1,9,13,17,21,25,30 1,9,13,17,21,25,30) and bench press (1,3 1,3). The available acute exercise and chronic training evidence suggest that a combined resistance approach (elastic bands plus free weights) may be more effective at enhancing strength and power than traditional resistance (free weights only), particularly during the back squat exercise. Interestingly, this seems limited to high intensities (≥75% 1RM) (1,3,23,30 1,3,23,30 1,3,23,30 1,3,23,30), as no differences have been reported when exercise intensity falls below 60% 1RM (25,30 25,30). Previous work from our team suggests that exercise mode (isometric vs. dynamic isotonic) and intensity (% 1RM) individually alter numerous kinematic variables (e.g., force-time, acceleration, etc.) (5,20,22 5,20,22 5,20,22). Detailed analysis of how dynamic variable resistance alters these important variables does not exist. Furthermore, the basic question of how much tension should come from bands vs. how much from free weights has received little attention (30). This knowledge gap is critical as differences in loading strategy likely alter kinematic variables important to sport performance such as the time it takes to attain peak velocity (PV), force, and/or power.
Considering the popularity among practitioners, the impressive initial findings, and the limited scientific evidence, clear need exists for the continued study of variable resistance. The deadlift exercise is of particular interest for 2 reasons. First, it (along with the squat) is one of the most implemented lifts for the general development of strength and power (31); however, it has not been examined with variable resistance. Second, although the squat and deadlift are the 2 exercises most typically associated with variable resistance training, kinematic analysis suggests that movement patterns differ vastly between the 2 exercises (17). This means that conclusions drawn from the back squat may not necessarily hold true for the deadlift. Therefore, the purpose of this study was to examine the acute kinetic characteristics during a deadlift exercise in combination with bands compared with a load-matched free weight only deadlift at moderate and heavy intensities.
Experimental Approach to the Problem
This investigation consisted of 2 interrelated studies. The first tested the force characteristics of the elastic bands (Jump-Stretch, Youngstown, OH, USA) over a range of static displacements (elastic modulus) (30). This was used to generate regression equations so that the amount of force coming from each band could be predicted at any distance (displacement). Data from study 1 were used to quantify the total load implemented in study 2. This second study compared peak force (PF), relative force (RF), average force (AF), maximum rate of force development (RFD), PV, average velocity (AV), peak power (PP), relative power (RP), average power (AP), time to peak ground reaction force (TPF), time between peak ground reaction force and peak power (PF → PP), time between peak ground reaction force and peak velocity (PF → PV), and time between peak power and peak velocity (PP → PV) during submaximal deadlifts (60 and 85% 1RM) performed with or without the inclusion of elastic bands (20). Detailed description of this process was described previously by our laboratory (20) and is similar to Ref. 30. These variables were chosen because previous work from our laboratory (5,20,22 5,20,22 5,20,22) and others (19) showed that they significantly relate to performance in dynamic multijoint tasks such as sprint cycling (27), jump performance (7,10–12,14 7,10–12,14 7,10–12,14 7,10–12,14 7,10–12,14), weightlifting outcomes (6,14 6,14), and throwing ability (26). All measurements were collected using a force plate (Advanced Mechanical Technology, Inc., Watertown, MA, USA) and velocity transducer (Model V-80-L7M; Unimeasure, Inc., Corvallis, OR, USA) and analyzed with LabVIEW (version 2013; National Instruments Corporation, Austin, TX, USA).
Bands used during the combined resistance (bands plus free weights) conditions were attached to anchors set in the floor at 2 positions (front and back) equivalent to the length of the bands (Figures 1 and 2). This length was chosen so that the bands were taut when added to a loaded barbell. In addition, a velocity transducer was attached to 1 end of the barbell. Participants were allowed to use their preferred hang grip placement, deadlifting shoes, and chalk, which all remained consistent for all conditions. No belts or straps were allowed.
Twelve resistance-trained males (age: 24.1 ± 2.4 years, height: 175.9 ± 5.4 cm, mass: 85.6 ± 12.5 kg, deadlift 1RM: 188.6 ± 16.1 kg) participated in the study. Participants were required to have experience performing deadlifts with elastic bands at least once a week for the past 6 months and be free of joint, musculoskeletal, and/or neuromuscular injury. Each participant was required to attend 3 trials on nonconsecutive days, separated by at least 48 hours. Before participation, each signed an informed consent document approved by the University Institutional Review Board.
The first study assessed the kinetic characteristics of the elastic bands (Table 1). Each pair of bands was stretched and measured over a range of displacements. This was achieved by placing a barbell on boxes at 14 different heights (ranging from 10.8 to 109.9 cm, in 7.6 cm increments) while resting on the force plate (Figure 1). The greatest length measured was near the stretch limit of the bands, beyond the level of all participants' bar height (average bar height for the participants was 81.8 ± 5.0 cm). The weight of the barbell and boxes was zeroed before the addition of the bands, ensuring only the force produced by the bands was measured. A pair of bands was then added to the bar in parallel fashion with the barbell positioned directly in the center of the bands and force plate. The bands were fixed to the ground through clips built into the floor. The center of the bands and placement of the barbell were permanently marked to ensure consistency. This setup was designed to simulate the standard way practitioners use these implements. Data were collected for 5 seconds. The bands were then removed and allowed to rest for 2 minutes to account for potential changes in elasticity. The kinetic characteristics for any length could then be calculated based on the elastic modulus of the bands (i.e., its quantified resistance to nonpermanent deformation; Table 1). Various combinations of bands were needed to generate the specific force requirements in study 2. Thus, 5 different thicknesses of bands were measured (pink, blue, red, purple, and green) in study 1. All bands were measured as pairs and none had ever been used before the study.
Study 2 was performed in a similar method as previous research on dynamic external resistance at various intensities (30). All primary testing was performed at both 60 and 85% of the participant's 1RM. Thus, testing required 3 days (day 1 = 1RM and familiarization, day 2 = 60 or 85% trial, and day 3 = 60 or 85% trial). Three conditions were examined in random order (2 variable resistance conditions and 1 traditional free-weight condition) at 2 intensities (65 and 85% 1RM). All the resistance during free weights (NB) came from traditional weight plates. Variable resistance condition 1 (B1) was performed such that 85% of the total resistance came from free weights and the remaining 15% came from the bands. Variable resistance condition 2 (B2) used the same concept, except had a higher percentage of resistance coming from bands (65% of the total resistance came from free weights and the remaining 35% came from the bands) (30).
Band tension was loaded so that the average resistance of the entire movement was equated across all 3 conditions and normalized to NB as done in a previous study (30): (a) the desired resistance for the participant was calculated (60 and 85% 1RM) and loaded onto the bar using free weights; (b) the desired value of resistance to come from the bands for the given condition was determined (equal to 15% [B1] or 35% [B2]); (c) half of the value from step (b) was then taken off the free-weight loaded bar; and (d) the bands were set up to provide the resistance value when the participant was standing erect, as calculated in step (b). It was important to equate the 3 conditions so that the average resistance produced by the bands did not exceed the free-weight condition.
Day 1: 1 Repetition Maximum Testing and Familiarization
Participants were required to use the conventional (as opposed to the “sumo”) stance, having their hands placed outside the knees. Participants warmed up by completing 10 repetitions at 50%, 5 repetitions at 70%, 3 repetitions at 80%, and 1 repetition at 90% of their estimated 1RM (30). They were given up to 5 single repetitions to determine their 1RM. Three minutes were given between warm-up sets and 5 minutes between 1RM attempts. Weight was increased in increments of 10–20 pounds, until they were able to complete only 1 repetition successfully. If they were not able to execute the lift successfully, the weight was reduced by 5–10 pounds. After the 1RM was determined, bands were attached to the barbell for a familiarization session. This included 3 sets of a single repetition at 50% of their 1RM. Participant's “finished position” bar height was measured and recorded at this time (Figure 2). The finished position bar height was measured as the height of the center of the bar when standing fully erect with the hips and knees fully extended. Consistent measurement of this position was needed so that the appropriate combination of band resistance (from study 1) and free weight could be loaded and matched for each trial.
Day 2 or 3: 60 or 85% Trials
Before each trial, participants performed a standardized warm-up consisting of high-knee walks, walking hamstring stretches, and walking lunges. Each movement was performed consecutively for 10 yards. This was immediately followed by a progressive deadlift warm-up that included 5 repetitions at 40%, 3 repetitions at 60%, and 3 repetitions at 80% 1RM. This was followed by 1 repetition at 80% 1RM with the addition of bands as it was important to simulate a warm-up consistent to a variable resistance condition. The amount of tension coming from bands during this final warm-up repetition was selected based on condition B1 so that 15% of the total resistance came from bands. This ensured the average tension was below all testing trials.
Testing then consisted of 3 single repetitions for each of the 3 conditions (NB, B1, and B2) for a total of 9 repetitions per day. All lifts were performed while standing on a force plate and with a velocity transducer attached to the end of the barbell. A 3-minute rest was given between repetitions of the same condition, with 5-minute rest between different conditions. Participants were encouraged to lift with maximum force and speed as soon as possible during each repetition.
All analyses were performed with IBM SPSS Statistics version 21.0 (SPSS, Inc., Chicago, IL, USA) and closely resemble that of Ref. 30. Alpha was set a priori at 0.05, and values are reported as mean (±SD). The first study tested the elastic modulus of each set of bands used in the study (this included 2 sets of pink, 2 sets of light blue, 2 sets of red, 1 set of purple, and 1 set of green) and allowed for linear regression analyses. For study 2, separate repeated-measures analyses of variance were used to analyze each of the following variables: PF, AF, RF, RFD, PV, AV, PP, AP, RP, TPF, PF → PP, PF → PV, PP → PV between conditions (NB, B1, B2) for each intensity (60 and 85%). Where appropriate, Tukey's post hoc comparisons were used. Standardized effect sizes (Cohen's d) analyses were used in interpreting the magnitude of differences between treatments. An effect size was classified as trivial (<0.20), small (0.20–0.49), moderate (0.50–0.79), or large (>0.80).
Force production was inversely related to band resistance (p ≤ 0.05) regardless of intensity (60 or 85% 1RM) for PF (d = 0.89 and 0.92, respectively), AF (d = 0.86 and 0.91, respectively), and RF (d = 0.84 and 0.88, respectively): NB > B1 > B2 (Table 2). There was no significant difference in RFD between conditions at 60% 1RM. However, at 85%, NB and B1 were less than B2 (p ≤ 0.05) and NB tended to be smaller than B1 (p = 0.051) (d = 0.54). Conversely, PV (d = 0.85 and 0.89, respectively) and AV (d = 0.86 and 0.80, respectively) were directly related to band resistance where NB < B1 < B2, regardless of intensity (Table 3). B1 and B2 produced significantly greater PP (d = 0.46), RP (d = 0.58), and AP (d = 0.42) than NB at 60% 1RM but were not different from each other. The same was true for AP at 85% 1RM (d = 0.85). However, bands produced significantly greater PP (d = 0.79) and RP (d = 0.79) (NB < B1 < B2) than NB at 85% 1RM. Time to peak ground reaction force (d = 0.47), PF → PP (d = 0.76), and PF → PV (d = 0.53) significantly decreased with the addition of bands where NB > B1 > B2 at 60% 1RM (Table 4). However, no differences were found between conditions for PP → PV. At 85% 1RM, differences in TPF (d = 0.43), PF → PP (d = 0.51), PF → PV (d = 0.43), and PP → PV (d = 0.33) were only significant for NB compared with B2, with time significantly decreased in B2 and a trend for NB > B1 for TPF (p = 0.074, d = 0.43), PF → PP (p = 0.083, d = 0.51), PF → PV (p = 0.056, d = 0.43), and PP → PV (p = 0.074, d = 0.33).
The purpose of this study was to examine the effects of combined elastic band and free-weight resistance during a conventional deadlift at moderate and heavy intensities. When compared with an average load-matched free-weight condition, the amount of force produced (peak, average, and relative) significantly decreased as the amount of total tension coming from bands increased, regardless of lifting intensity (i.e., 60 vs. 85% 1RM). Conversely, velocity (peak and average) increased as band resistance increased. Unlike force and velocity, the amount of total tension (60 vs. 85% 1RM) influenced power at times (8). PP, AP, and RP increased with the addition of bands, but the amount of tension coming from bands was unrelated (NB < B1 and B2). However, PP and RP increased with an increase in band tension when lifting at higher intensities (NB < B1 < B2). Maximal RFD was generally unaffected by absolute load, or band tension, but interpeak variables (TPF, PF → PP, and PF → PV) were significantly reduced at light and heavy loads with the addition of bands. Taken together, these results indicate that the addition of heavy resistance bands alters the kinetic characteristics of the deadlift exercise and both (a) the amount of band tension and (b) the total lifting intensity matter.
Our methodological approach was to use average tension to normalize the variable resistance condition to a load-matched free-weight condition. In other words, the load at rest was higher during the NB condition (because the bands were providing no tension). This likely explains the sequential decrease in force (AF, PF, and RF) and increase in velocity (AV, PV) with an increase in band tension (i.e., less load on the bar at rest). In opposition, Stevenson et al. (25) chose not to equate the average tension of their band and no band trials and found AV and PV were significantly higher in their no band condition. The comparison of 2 entirely different loads can probably explain the decrease in velocity they noted with bands.
Wallace et al. (30) used a mathematical approach similar to ours to examine dynamic variable resistance (using heavy bands) during the back squat. In opposition to our findings, they reported no difference in velocity measures between conditions and that force increased with an increase in band tension. However, similar to us, they noted that RFD was unaltered by bands at either moderate loads. Unlike the back squat, a single repetition deadlift is initiated as a concentric movement that must overcome inertia of the bar. This likely explains the divergent findings and makes our choice to examine the deadlift novel and practically important. Cronin et al. (9) highlighted the importance of recognizing movement specificity by showing that performance variables differ significantly between each exercise. The back squat and deadlift differ kinetically and kinematically in numerous ways but particularly in their failure locations (17). Force production is only maximized during the portion of any movement that optimizes body positions and joint angles (2,25,30 2,25,30 2,25,30), making it difficult for isotonic exercises to challenge the mechanically advantageous positions. Theoretically, bands challenge these positions. This suggests that elastic bands will have the greatest influence at greater intensities.
To our knowledge, only 2 other studies have examined intensities at or below 60% 1RM (25,30 25,30) and both support our findings that the specific influence of bands depends on the loading intensity (30). Force and velocity were sequentially affected by the amount of band tension, and this relationship was not different at heavier or lighter absolute loads. However, the load did alter how the bands influenced power, RFD, and interpeak variables. More tension from bands generally meant more power when lifting at heavy loads; however, the amount of band tension may not matter for power when lifting at moderate loads. Rate of force development was generally unaffected by the bands, with the exception of the heavy band (B2), heavy load (85%) condition. A similar study also reported no effect of bands on RFD at either intensity (30). Yet, a further examination of the force-time curve revealed significant changes in interpeak variables with the bands at both intensities and provides insight about RFD.
Force production during the first 0.3 seconds (300 milliseconds) of action is particularly important for explosive movements (20). Interestingly, although the addition of bands during the 60% condition did not alter RFD, it did significantly reduce the time to PF to less than 0.3 seconds, with more bands causing more reduction. Work from our laboratory and others (4,16 4,16) highlights the practical importance of these findings as some interpeak variables significantly correlate to whole-body performance measures such as the vertical jump (20), which occur in roughly 0.25 seconds (4,16 4,16). The time between PF and PP and the time between PF and PV were also reduced with the progression from no bands, to light bands, to heavy bands. The same pattern existed during the 85% condition but only displayed a significant difference for heavy bands (vs. light and no bands) and a trend for the light bands (vs. no bands). Moreover, RFD was only different at the heavy band, heavy load condition. Our examination of interpeak variables collectively suggests (a) that bands help synchronize PF, velocity, and power and (b) that a particular uniqueness exists when combining heavy band tension with heavy absolute load. Thus, although they are in need of more direct and rigorous investigation, interpeak variables clearly provide unique detail and insight beyond that of maximal RFD.
In summary, the addition of heavy elastic bands to the deadlift exercise significantly alters numerous kinetic variables. This seems movement specific as the changes demonstrated here differ from similar work involving the back squat. Both the absolute load on the bar and the percentage of resistance coming from bands vs. free weight is important. Practitioners should consider these implications when making programming choices. More research on dynamic variable resistance is needed as the acute nature of our study does not describe chronic adaptations.
The results of this study suggest that the acute addition of band tension generally increases power and velocity while simultaneously decreasing the time to reach PF and the time between force, power, and velocity peaks, especially when performed at moderate absolute loads. However, this strategy reduces force production. Our findings also suggest that both the absolute load and the amount of band tension significantly change kinematic variables. Thus, practitioners should consider which kinematic variables are of most importance to that particular training session when contemplating adding heavy elastic bands. This information should also influence both the amount of band tension applied and the absolute movement load.
For example, a training session designed to emphasize power (and/or the synchronization of maximal force/power/velocity) in the deadlift might implement the bands. Moreover, the tension coming from bands should represent a significant amount of total load. Practitioners should likely opt for more free-weight resistance, with minimal or no heavy bands, if maximal force is the primary exercise goal. Our results may or may not apply to less-experience lifters than the ones tested here, as the technical proficiency requirement of lifting with heavy bands is extremely high (especially at heavy loads).
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Keywords:Copyright © 2015 by the National Strength & Conditioning Association.
power; dynamic variable resistance; velocity; human strength curve; strength