A relatively new method of providing resistance for free weight exercises is the use of supplemental heavy chain resistance (SHCR) in addition to the traditional free weight plate resistance (1,2,5). This technique is not common but has been used in selected powerlifting gyms for the past several years, primarily with large, multijoint exercises such as the back squat and bench press exercises (6). The back squat and bench press both exhibit an ascending strength curve (4), which allows an individual to lift more weight at the top portion of the lift than at the bottom. The premise behind using supplemental chains is that they provide a variable resistance that accommodates this ascending strength curve, providing limited resistance at the bottom of the lift, yet progressively providing additional resistance as the lift is completed (1-3,5,7). As the barbell is eccentrically lowered toward the bottom of the lift, a portion of the chain links are lowered onto the floor, progressively decreasing the resistance provided. As the barbell is lifted upward, additional resistance is provided as chain links are sequentially lifted off the floor.
The set-up and use of SHCR for the back squat has been discussed briefly. Dermody (2) and Simmons (6) describe a double-looped technique that uses a smaller chain to position a heavier chain. At the bottom of the lift, Simmons reports that approximately 50% of the chain will be piled up on the floor, depending upon the length and depth of the lift. A linear hanging technique has also been described and illustrated (1,5). With this method, the heavy chain is affixed directly to the barbell, through various carabiner clips or clamps, and hangs in a linear fashion from the barbell to the ground. This linear technique results in a significant portion of the chain simply acting as static weight, with only the lower portion of the heavy chain providing variable resistance as it contacts the floor. Both techniques recommend 2 to 3 links of chain resting on the floor at the beginning of the lift to minimize chain oscillation and sway (2,5,6).
Currently, only 1 research article has been published studying the squat exercise using SHCR. Ebben and Jensen (3) performed an electromyographic and kinetic study comparing motor unit activation, rate of force development, and peak force development in back squats with resistance being provided by traditional weights, heavy chains, and elastic bands. Their study did not support the use of heavy chains or bands as resistance with squat exercises. However, their article provided little description of how the chains were set up, the weight of the chains, and the percentage of plate weight resistance used. A few of these limitations were pointed out in an instructional article, including information it was a 1-time training session and that the actual amount of weight on the bar was not provided (2).
This practice of using SHCR is gaining acceptance in collegiate and high school weight rooms around the country; however, little research exists regarding the proper use of chains and how much load is actually provided when using chains in different manners. The purpose of this study is to determine the actual resistance being provided by a double-looped versus a linear hung SHCR to the back squat exercise.
Experimental Approach to the Problem
This study was designed to be descriptive in nature, measuring the actual amounts of resistance provided by 2 different application techniques of SHCR, double-looped and linear hung. In addition, a comparison of the percentage of chain resistance unloaded at the bottom of the squat during the 2 techniques was performed.
One experienced and trained male weight lifter (age = 33 yr; height = 1.83 m; weight = 111.4 kg) familiar with using supplemental chain resistance was analyzed while performing a back squat exercise. Institutional review board approval was received from the Committee on the Use of Human Subjects, Bradley University. The subject, a co-author for the investigation, was fully aware of any risks associated with his participation in the study.
To obtain the exact resistive force applied by the SHCR, a pair of load cells, Omega LC703-75 (Omegadyne, Inc., Sunbury, OH, USA), was used. The load cells and SHCR were attached to a York Elite Olympic Barbell by way of a standard 50.8 mm (2 inch) sleeve collar. The load cells provided an analog signal that was sampled at a frequency of 500 Hz. The analog signals were powered and amplified using Omega Model DMD-465 Powered Bridge Sensors (Omegadyne, Inc., Sunbury, OH, USA) with signal conditioning. The signal was converted to a 12-bit digital format using a National Instruments PCMCIA DAQCard-6024 (National Instruments Corp., Austin, TX, USA) portable analog-to-digital converter and LabView software (National Instruments Corp., Austin, TX, USA). The digital signal was processed with an Apple laptop computer using a Microsoft EXCEL spreadsheet. The uncertainty in the force measurement was estimated at 0.5 Newtons.
The heavy chains used for this study were 15.9 mm (5/8 inch), 1.52 m (5 ft) long, and weighed 7.9 kg, whereas the smaller adjusting chains were 6.35 mm (.25 inch), 1.83 m (6 ft) long, and weighed 1.7 kg (2,6). The chain resistance was connected to each load cell by way of a carabiner clip (Figure 1). The SHCR was applied in 2 different manners, the double-looped technique, using the 6.35 mm chain to position the heavy chain closer to the ground (2,6), and the linear technique, with the chain hanging directly from the barbell (1,5). Figure 2 shows these 2 techniques at the maximum depth squat position. Note the amount of heavy chain still hanging versus the amount piled on the floor in these 2 different techniques.
Before data collection, the subject performed typical dynamic warm-up exercises and warm-up squats. Plate weight resistance was set at 83.6 kg (184 lbs), approximately 50% of the subject's self-reported 1 repetition maximum (2,6). Data were collected for 1 set of 3 repetitions (2,6) under the following 4 test conditions: double-looped 1 chain, double-looped 2 chains, linear 1 chain, and linear 2 chains. A minimum of 5 minutes rest was provided between each subsequent test condition.
The amount of variable resistance provided by the chains was defined as the difference between the minimal load cell resistance at the bottom of the lift and the maximum resistance at the top of the lift. Variable resistance efficiency was defined as the ratio of variable chain resistance provided compared with the maximum chain resistance provided at the top of the lift, expressed as a percentage. This percentage represented how much of the chain weight was actually variable, being unloaded at the bottom and reapplied as the lift moved vertically upward. For all measurements, the load cell readings from the right and left load cell were added together to obtain a total resistance reading.
Average load cell values for the maximum load at the top of the lift, minimum load at the bottom of the lift, amount of variable resistance, and the variable resistance efficiency are presented in Table 1. It should be noted that these data are based on the actual amount of resistance provided by the chains throughout the lift. The maximal load at the top is not the total weight of the chains because 2 to 3 links are resting on the floor, thus providing no resistance.
Little published research on the proper use or effectiveness of strength training with SHCR exists. This study did not set out to determine whether the use of SHCR was more or less effective than using traditional free weights when performing back squat exercises. Because of the lack of uniformity in the use of SHCR, this study set out to provide a description of the resistive forces present with SHCR when using 2 different techniques, double-looped and linear hung. The starting position for the squat exercise is at the top of the lift. The resistance must be eccentrically lowered toward the bottom of the lift, the weaker part of the lift according to the ascending strength curve, followed by the concentric lifting of the resistance upward toward the top of the lift, the stronger part of the lift (4). When using the double-looped method, we found that nearly 80-90% of the chain weight at the top of the squat was unloaded on the floor at the bottom of the squat. This means that, as the bar ascended, 80-90% of the chain weight was progressively added back to the squat as the chain was sequentially lifted from the floor. In contrast, when using the linear hung method, we found that only 35-45% of the chain resistance at the top was unloaded at the bottom of the squat and thus added back as the squat was completed, the remainder basically serving as static resistance. Regardless of the actual weight of the chain used, we would expect similar percentage differences to exist between using the double-looped compared with the linear hung method.
No other published reports have studied the actual amount of variable resistance provided when using SHCR. This study suggests that there is nearly a 2-fold difference in the amount of variable resistance provided between the double-looped and linear hung method of SHCR when performing the back squat. The same percentages of variable resistance provided by using SHCR may not apply to all lifters. The subject in this study was 1.83 m tall and performs back squats to a depth where the midthigh is nearly parallel. The combination of the height of our subject and the depth of his squat resulted in approximately 0.75 m of chain being lowered onto the floor. Different height lifters and those that perform deeper or shallower squats will experience a different length of chain being unloaded at the bottom of the squat. This, in conjunction with the technique for hanging chain, will ultimately determine the amount of variable resistance provided to the lift. This thought can apply to the bench press as well. Lifters with differing arm lengths or chest diameter require the bar to move different distances. The further the bar moves vertically, the greater amount of variable resistance is provided. To maximize the variable resistance offered by SHCR, consider using the double-looped method for attaching the chains to the barbell. It might be slightly more complex when properly adjusting and positioning the chains, but will provide a greater amount of variable resistance to the lifts.
The benefit of providing variable resistance to an exercise with an ascending strength curve is that additional resistance can be provided as the lift becomes easier toward the top of the lift. When hanging SHCR from a barbell during a vertical exercise, the overall resistance provided by the chain decreases as the bar is lowered toward the bottom of the lift and then progressively increases as the bar is raised and chain links are sequentially lifted off of the ground. If the intent of using SHCR is to provide a large amount of variable resistance throughout the range of motion of a back squat, this study demonstrates that using the double-looped method can provide approximately 2 times the variable resistance compared with the linear hung method. When using the linear method to hang heavy chains, nearly 50% of the weight of the heavy chain simply acts as static weight resistance, never reaching the floor to provide any variation in resistance.
The authors thank the College of Engineering and the College of Education and Health Sciences' Center for Research and Service, at Bradley University, for providing funding to purchase necessary equipment to complete this study.
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Keywords:© 2010 National Strength and Conditioning Association
strength training; weight training; exercise; biomechanics