Effects of Short-Term Jump Squat Training With and Without Chains on Strength and Power in Recreational Lifters

Background: The use of chains in resistance training is a way to accommodate the muscular strength curve. Short-term training and jump squats have been shown to increase back squat strength, but not in conjunction with each other or with chains. Jump squats have also been used to increase jump height and power. Objectives: The purpose of this study was to investigate the effects of short-term jump squat training with and without chains on strength and power. Methods: Thirty-one resistance-trained men volunteered to participate (age = 23.87 ± 2.2 years, height=174.87 ± 6.94 cm, mass = 82.74 ± 14.95 kg) and were randomly assigned to one of three groups [control (C) = 10, no chains (NC) =10, or chains (CH) = 11]. Participants had their jump height (VJ) and back squat strength (BS) tested before and after a week of training. The NC and CH groups performed three training sessions consisting of five sets of three reps of jump squats at 30% 1RM with 30s rest between sets. The CH group had 20% of their load added by chains when standing erect. The C group did not train. Results: A 3 (group: CH, NC, C) x 2 (time: pre, post) mixed factor ANOVA revealed a significant (p = 0.006) interaction for back squat 1RM. Both the CH (pre 142.56 ± 20.40 kg; post 145.66 ± 19.59 kg) Flourishing Creativity & Literacy IJKSS 4(4):18-24, 2016 19 and NC (pre 150.00 ± 15.23 kg; post 154.77 ± 15.09 kg) groups significantly increased while the C (pre 157.27 ± 25.35 kg; post 156.36 ± 24.85 kg) group showed no difference. There were no significant interactions (p =0.32) or main effects for VJ (C = pre 50.59 ± 9.39cm; post 51.29 ± 9.68cm; NC = pre 55.29 ± 5.23cm; post 57.39 ± 5.22cm; CH = pre 46.19 ± 5.02; post 47.45 ± 4.62.) Conclusions: The CH group was able to increase strength while lifting less overall weight. Coaches may use short-term training with chains to yield a similar increase in back squat strength as without chains.

A popular program, variable resistance training, has also been shown to increase strength and power.Variable resistance training uses elastic bands or chains to add resistance during different parts of the lift depending on where they are applied.Specifically, in a back squat, resistance is added during the concentric phase due to more chain coming off the floor (McMaster, Cronin, & McGuigan, 2009;McMaster, Cronin, & McGuigan, 2010;Neelly, Terry, & Morris, 2010).Elastic bands and chain length and width alter resistance (McMaster, Cronin, & McGuigan, 2009;McMaster, Cronin, & McGuigan, 2010;Wallace, Winchester, & McGuigan, 2006).However, bands have a curvilinear length/tension relationship while chains have a linear length/tension relationship (McMaster, Cronin, & McGuigan, 2009;McMaster, Cronin, & McGuigan, 2010).
Long term training can increase strength and power but short-term training has also has shown to increase strength and speed (Brown & Whitehurst, 2003;Coburn, Housh, Malek, Weir, Cramer, Beck, & Johnson, 2006).Brown demonstrated that two visits increased velocity of isokinetic knee extensions; while Coburn found that three visits increased isokinetic knee strength.However, limited research has combined power training in the short-term.
Powerlifters have implemented variable resistance in their training to increase strength (Swinton, Stewart, Lloyd, Aqouris, & Keogh, 2012).Additionally, it has been shown to increase force, strength, and power of the upper (Ghigiarelli, Nagle, Gross, Robertson, Irrgang, & Myslinski, 2009) and lower body (Israetel, McBride, Nuzzo, Skinner, & Dayne, 2010;Rhea, Kenn, & Dermody, 2009;Wallace, Winchester, & McGuigan, 2006 ).However, limited research has examined short-term variable resistance training to specifically increase jump height.Therefore, the purpose of this study was to investigate the effects of short-term jump squat training with and without chains on strength and power.

Participants
Thirty-one healthy males (age=23.87±2.2 years, mass= 82.74 ± 14.95kg, height =174.87±6.94cm) volunteered to participate and were randomly assigned to either a chain (CH=11), no chain (NC=10), or control group (C=10).The requirements for participation were that each subject had been resistance training for at least one year, at least three times a week, and could squat at least 1.5 times their body weight with a minimum of 200 lbs.On testing and training days they were asked to not perform any lower body exercises or strenuous activities and not supplement with creatine.All subjects were kinesiology students recruited from classes.All testing was performed in a laboratory setting.On the first day they read and signed a university Institutional Review Board approved informed consent document.

Procedures
Prior to testing, participants' mass (ES Series Bench Scale, Ohaus Corporation, Pine Brook, NJ) and height (ProDoc Series DHRWM Digital Height Rod, Cardinal Scale MFG, Webb City, MO) were measured.Participants then performed a dynamic warm up consisting of walking knee hugs, lunges, and Frankenstein's for 20 m each.These exercises were used to warm up the lower body (Brown, Weir, 2001).

Vertical Jump Testing
After the warm up, participants performed two practice countermovement jumps before three maximal jumps using a vertical jump test apparatus (Jones, Brown, Coburn, Noffal, 2015) (Epic Combine Jump Station).If they touched any vanes on the third attempt, they continued jumping until they could not jump any higher.The best trial was used for data analysis.Reliability of the vertical jump test was ICC = 0.98.

1RM Back Squat Testing
For the back squat, a safety squat device (Safety Squat; Bigger Faster Strong, Salt Lake City, UT) was used to ensure that each participant squatted to parallel at the top of the quadriceps.They warmed up by squatting 10 repetitions at 50% of their predicted 1RM, five repetitions at 70%, three repetitions at 80%, and one repetition at 90%.They then had a max of five attempts to reach their 1RM.There were 3 min of rest between warm up and max attempts (Brown, Weir, 2001).

Training
There were three training sessions total and the NC and CH groups performed jump squats for five sets of three repetitions with 30 s rest (Moreno, Brown, Coburn, Judelson, 2014).They were instructed to perform a quarter squat and jump as high as possible.Each session was separated by 48 hrs.The C group was instructed to not do any lower body training for the entire week.

Load
The load for the CH and NC group was matched at approximately 30%1RM (Nijem, Coburn, Brown, Lynn, Ciccone, 2016).The weight for the CH group was quantified by having subjects stand upright with an unloaded barbell.Large chains were suspended from smaller chains in a double loop method (Figure 1).Chains were then added to each side until the desired load of 20% was reached.The remaining weight was then added to the bar via weight plates to equal the prescribed 30% 1RM load.The weight for the NC group came entirely from weight plates on the bar.

Back Squat 1RM
There was a significant (p = 0.006) interaction of group x time.Both the CH and NC groups showed a significant increase from pre to post while the C group showed no change (Table 1).There were no significant differences between the CH and NC group.

Vertical Jump
There were no significant (p = 0.32) interactions or main effects for time (p = 0.63) or condition (p = 0.11) (table 2).

Discussion
The purpose of this study was to determine the effects of short-term jump squat training with and without chains on strength and power.The major finding was that 1RM back squat strength increased for both the CH and NC groups with no change in the control group.These results may be due to neurological adaptations such as increased motor unit recruitment or firing rate (Aagaard, Simonsen, Andersen, Magnusson, Dyhre-Poulsen, 2002;Cormie, McGuigan, & Newton, 2010;Cormie, McGuigan, & Newton, 2011;Gabriel, Kamen, & Frost, 2006).
Short-term resistance training can result in neural adaptations in the absence of hypertrophic changes, such as increased motor unit firing rate (Gabriel, Kamen, & Frost, 2006).Increasing firing rate has been shown to increase muscular force (Cormie, McGuigan, & Newton, 2010;Gabriel, Kamen, & Frost, 2006).High firing rates are also important for increasing rate of force development (Aagaard, Simonsen, Andersen, Magnusson, Dyhre-Poulsen, 2002;Ratamess).Another adaptation is motor unit recruitment.Motor units move from smaller slow-twitch to larger fast-twitch depending on the load or speed of the movement (Gabriel, Kamen, & Frost, 2006, Ratamess).Movements that are slow and light use primarily small motor units while heavy, fast, and explosive require large motor units (Ratamess).
Previous research has shown that these adaptations can occur in only one week.Brown (Brown & Whitehurst, 2003) and Coburn (Coburn, Housh, Malek, Weir, Cramer, Beck, & Johnson, 2006) studied the effects of short-term training with two or three visits respectively.Brown found that two visits showed an increase in velocity, but not force, while Coburn found that three visits showed an increase in force.Tillin et al. (Tillin & Folland 2014) examined the short-term effects of maximal vs. explosive strength training in an isometric knee extension.They found that maximal training resulted in greater improvement in voluntary contractions, but explosive training had a greater increase in early phase force.Both of these adaptations occurred at the onset of training and promoted strength gains.The current study supports this as short-term explosive training increased strength gains and early phase force.
Variable resistance has been used in different types of training.The use of bands or chains are designed to alter the strength curve of an exercise.This causes the load to increase as the lifter rises during the concentric action and can be more explosive (McMaster, T., Cronin, J., McGuigan, 2009).Rhea (Rhea, Kenn, & Dermody, 2009) found that the use of bands with fast movements increased peak power greater than slow heavy movements yet both similarly increased maximal strength.The current study also demonstrated that variable resistance increased strength.However, power was unaffected in their study, which may have been due to the relatively heavy loads used.Galpin (Galpin et al., 2015) also examined the effects of different loads using variable resistance.Their study used banded deadlifts at 60% and 85% 1RM using different resistances (B1=15% resistance, B2 = 35% resistance.)Results showed that force decreased as tension increased.However, velocity was greater for the two banded deadlift conditions at 60% than the free weight deadlift, but B2 was greatest at 85% 1RM.Peak power was also higher for the banded conditions than with free weights.This current study used a lighter intensity and found an increases in strength for the CH and NC groups, but no changes in power for any group.
McCurdy (McCurdy, Langford, Ernest, Jenkerson, & Doscher, 2009) also found that training with and without chains increased strength.They compared the bench press with chains supplying all of the weight to plate loaded alone.Both increased strength with no significant differences between conditions.In the current study, the CH group trained with less overall weight, but still showed a significant increase in strength.We hypothesized that the chain group would have a greater increase in vertical jump height due to lifting less weight with greater speed and acceleration.However, this was not the case as no group demonstrated a change in vertical jump height.The weight that the chains provided was a relatively light load, so there may have only been a small increase in acceleration during the concentric phase.
There have been few studies examining the load that chains supply to a lift.A study by Nijem (Nijem, Coburn, Brown, Lynn, & Ciccone, 2016) had subjects perform deadlifts using a load of 20% of the weight supplied by chains at the top of the lift.The current study used the same loading scheme, but used the double loop method to suspend the chains from a standing position which supplied more variable resistance than having the larger chains hanging directly to the floor (Neelly, Terry, & Morris, 2010).The load supplied by the chains for the CH group was matched to the NC at 30%1RM.One possible reason why there were no significant differences was that the CH group lifted less total weight.Matching the total weight at the bottom of the jump squat may have resulted in greater power or strength gains.
McBride (McBride, Triplett-McBride, Davie, & Newton, 2002) examined the effects of eight weeks of jump squat training using light loads (30%1RM) or heavy loads (80%1RM).Both groups had an increase in strength, but the lighter load group also increased velocity.However, other studies have identified different intensities for optimal peak power.
Adequate volume and frequency are required to increase power.Cormie (Cormie, McGuigan, & Newton, 2010) examined the effects of 10 weeks of power training and found that seven sets of six repetitions at 0%1RM twice a week with five sets of five repetitions at 30%1RM once a week caused an increase in power for both strong and weak individuals.The current study used five sets of three repetitions for only three visits resulting in an increase in strength for both groups, but not explosiveness.Perhaps a longer study may have positively influenced power.
Variability is needed in a training program to decrease staleness.One way to add variety to a program is by using novel training as it provides a new type of stressor (Haff, Hobbs, Haff, Sands, Pierce, & Stone, 2008).Resistance training is novel to untrained individuals, and they will normally experience some type of improvement (Gamble, 2008).Another type of novel stressor is kettlebell training.Otto (Otto, Coburn, Brown, & Spiering, 2012) (Gamble, 2008).Studies have shown that specific training has greater transferability (Barak, Ayalon, & Dvir, 2004, Cale-Benzoor, Dickstein, Arnon, & Ayalon, 2014).The current study demonstrated that jump squats had greater transferability to the back squat than to the vertical jump.The squatting portion of the jump squat directly resembles the back squat.Although the jump squat utilizes triple extension of the knee, hip, and ankle, the training did not transfer to an increase in jump height.This could be due to the load of the jump squats being more than body weight, so acceleration, force, and power were altered.

Conclusion
The findings of the current study demonstrate that short-term jump squat training with or without chains increased 1RM back squat strength.The chain group, while lifting less overall weight, was still able to increase their 1RM strength.However, the training intensity, volume, or duration was not sufficient to increase power.Further research should focus on a longer duration of training and also examine matching chain loads at different positions of the lift.Coaches and athletes may use short-term training with chains to yield a similar increase in back squat strength as traditional loaded jump squats.Coaches and athletes can also use this type of training as a taper to reduce volume without risking a decrease in back squat strength.This jump squat training scheme may be beneficial if time is limited as the training was only approximately three to five minutes.

Figure 1 .
Figure 1.Barbell with double loop chain load
compared the effects of kettlebell swings to Olympic weightlifting during a 6-week training program.They found that both forms of training increased strength in the back squat, but the increase with weightlifting was greater.The current study was not as long as Otto, but also showed that novel training can increase strength.Specificity of training is also needed for a training program.Transferability is how well the specific training transfers to a movement or skill