By Joe Eisenmann, PhD
“You can’t fire a cannon from a canoe.”
“Don’t build on sand.”
“Build the foundation of the house before you put up the walls.”
In the context of athletics, these analogies highlight the importance of lower body strength as a foundation to athletic performance. Indeed, several studies have shown that lower body strength is related to acceleration, sprinting speed, change of direction, jumping ability and even throwing velocity (baseball) and throwing distance (field events).
The cornerstone exercises for developing lower body strength and power are the barbell squat, deadlift, and the Olympic lifts and/or their derivatives (hang clean, jump shrug, high pull, etc.). These compound, multi-joint exercises are most often performed with a constant external load (e.g., plates on the barbell) throughout a full range of motion. It is essential that the athlete is taught proper technique given the heavy loads that can be lifted. Once the athlete can perform these exercises in a technically sound manner, strength gains can be monitored via a 1RM or estimated 1RM.
During heavy loading, it is common for an athlete to experience a ‘sticking point’ during the exercise – or that point during the exercise that is just a bit more difficult. This sticking point is a result of biomechanical disadvantages at certain joint angles (think lever systems). To overcome the sticking point, athletes and strength coaches have utilized bands and chains to vary the load throughout the range of motion of the movement – this method is known as variable resistance training. This concept essentially implies that as the exercise gets easier the load gets heavier as the band stretches.
EFFECTS OF VARIABLE RESISTANCE TRAINING
A meta-analysis (a statistical technique that combines the results of all the studies and produces 1 common statistic) of 7 published studies that included 235 trained and untrained subjects who trained for 7+ weeks in duration found that variable resistance training led to a significantly greater average strength gain (average difference: 11 lbs; 95% confidence interval: 5-17 lbs) than the gain recorded in response to conventional weight training.
Likewise, a recent review of the published literature (Suchomel et al. Sports Med, 2018) identified that variable resistance training produces the greatest comprehensive adaptations in muscle size, strength, and power compared to other methods.
In a classic study of NCAA male athletes at Arizona State University, legendary strength coach Joe Kenn and Dr. Matt Rhea randomly assigned athletes to 1 of 3 velocity-based training groups for a 12-week period:
- group 1 – heavy resistance/slow movement (0.2-0.4 meters/second)
- group 2 – lighter resistance and fast movement (0.6-0.8 meters/second)
- group 3 – fast movements with variable resistance (0.6-0.8 meters/second).
The improvements in peak force and peak power during the squat are shown below:
|GROUP||Change in Peak Force||Change in Peak Power|
|Heavy resistance/slow movement||9.6%||4.8%|
|Lighter resistance/fast movement||3.2%||11.0%|
|Fast movement with variable resistance||9.4%||17.8%|
The authors concluded that variable resistance training performed with elastic bands and fast movement appears to provide greater performance benefits with regard to peak force and peak power than heavy, slow resistance exercise.
VARIABLE RESISTANCE AND THE DEADLIFT AND OLYMPIC LIFTS
Unlike the set-up for anchoring the cords or bands on the rack, the downfall of loading with variable resistance on the deadlift and Olympic lifts has been securing the cords or bands to the platform. The Perform-X Trak-X™ System has provided a solution to this problem by providing a safe and secure anchoring system to allow variable resistance loading for the deadlift.
To date, only one study by Dr. Andy Galpin and colleagues has examined the influence of variable resistance loading on the deadlift and this study only examined the acute effects comparing velocity, force, and power between free weight and variable resistance at 15% and 35% of resistance from bands. To our knowledge, there is no published literature on cord-loaded variable resistance of the Olympic lifts.
IMPROVING LOWER BODY POWER THROUGH PLYOMETRICS
As mentioned above, traditional strength training along with variable resistance training can improve neuromuscular power. Although strength is said to be the bedrock of neuromuscular power, it is common practice to include ‘jump training’ or plyometrics in strength and conditioning programs with the aim of improving lower body power.
Jump training can be performed with body weight, loaded (resisted) or assisted. For example, a jump squat can be performed freely with one’s own body weight, whereas loaded or resisted jump training is performed with an added external load such as a barbell, dumbbells, weighted vest, or resistance cords. Cord or band-assisted jumps (think bungee jump!) can also be performed as a plyometric exercise.
A natural progression to body weight squat jumps are resisted jumps. Many strength coaches prescribe barbell squat jumps at lighter loads approximating 30-60% of 1RM. There is some concern for the safety of this approach. An alternative to the barbell jump squat is a squat jump machine such as the Jump-X™. The Jump-X™ is unique in that it allows traditional pressing and jumping for both double- and single-leg applications, and also offers both resisted and assisted variable loading.
Besides the squat jump, another approach to resisted jumps is to use elastic cords or bands. The Vertimax is a commercially-available resistance jumping device that some programs have used to incorporate this approach. Research utilizing the Vertimax in high school and collegiate athletes has shown significantly greater effects on lower body power compared to traditional strength training and plyometrics alone. However, this device is costly and cumbersome.
A durable and versatile alternative to the Vertimax can be found with the Perform-X Inlaid platform and Trak-X system. Besides the usability for variable resistance training for the deadlift and Olympic lifts as described above, the Jump-X™ System also allows for cord-loaded vertical jump and footwork training on the Lift-X Platform. This system can also be retrofitted onto existing above ground platforms to form a plyometric station.
SUMMARY: “The legs feed the wolf.”
A strong and powerful lower body is vital for athletic performance. The lower body provides a base for running, jumping, changing directions and also serves as the engine in the kinetic chain for upper body movements. Thus, there is considerable interest in developing lower body strength and power among coaches and athletes. As shown in the research, variable resistance training that includes the cornerstone lifts and plyometrics of the lower body results in superior gains in muscle size, strength and power.