[This is a guest blog from Jenna Burnett. Jenna has a Bachelors degree in physics and mathematics from Purdue University and is working on her Masters in kinesiology at Iowa State University. She is currently working as a Sports Science Research Intern at Athletic Lab.]
[Note from Mike Young: This post is the 2nd in a 3 part series on the Exxentric kBox3. The kBox3 is a critical training tool for us at Athletic Lab and, as with any new sport technology we integrate, we test the equipment to not only ensure the data it produces is accurate, valid and reliable but also to determine best practices for its subsequent use. We regularly conduct in-house testing both for the companies and for ourselves and have published some of this data on this and other blogs. In this series, Jenna looked at various loading protocols for the kBox on the most commonly used exercise: the Kbox Squat.]
This is the second installment of the three-part series discussing power capabilities in different loading situations and using different harness systems for the Exxentric kBox3. If you missed the first part or need a reminder, you can read it here. In this second installment we’ll look at the methods and results from the data collection. Part three will be posted later and will include the discussion and conclusions.
The participants were recruited from the summer 2016 intern group and employees of the Athletic Lab located in Cary, North Carolina. The participants ranged in age from 20 to 31 and all were recreationally fit. The participants consisted of 3 females and 9 males. Due to limitations in sex distribution, the differences in power between the male and female participants was not considered for this testing protocol. All participants had never used the kBox3, requiring familiarization and explanations before completion of the data collections. Before participating, individuals were allowed to warm up if they chose and fatigue was limited by performing the protocols either before a workout or after a significant amount of time had passed since the end of workout. Individuals who had lower limb injuries or limitations were excluded from participation.
The participants were put through a minimum of seven sets of two pre-squats and five full depth squats, with the potential for eight sets if one set did not meet the minimum depth requirements of 45 cm or due to technology problems. The male participants used 0.075 kg*m2 flywheels for inertia, while the females used 0.050 kg*m2 flywheels. The sets were split into two different testing days to both allow recovery and accurate data, as well as to switch the harness system between the vest and the hip harnesses. The first day, the participants were put through two familiarization sets with the kBox3 to allow for the lack of experience with the eccentric overloading, and to get baseline peak power values. The third set consisted the isometric hold set, called the pinch protocol. The participants were spun down to approximately a quarter squat and held in that position for a slow count of 5. At the count of 5, the participants were asked drive upwards and initiate the isometric hold. After they were released, they continued to drive upwards and began the five full depth squats. For the final set, the lag protocol, a lag in the cord was created by adding an additional four inches of cord. The participants were then asked to do a set of two pre-squats and five full depth squats with the additional cord. Between each set, participants rested between three and five minutes or until they felt fully recovered. For the second day of testing, most participants completed only three sets, as the two familiarization sets were not needed. The protocols used for the second day were consistent with the first, with the only changes being the one familiarization or baseline set and the use of the hip belt rather than the vest harness. For each set, the absolute peak power was recorded for both the eccentric and concentric squat movement. The absolute peak power values for each individual were then plotted in Matlab to allow for comparison.
Strict Concentric Plots
Concentric Peak Power with the Vest Harness
For the concentric peak powers, four participants had their highest peak power in the pinch protocol. Seven participants had their highest concentric peak power in the lag protocol and only one individual had their highest concentric peak power in the familiarization protocol.
Concentric Peak Power with the Hip Belt
For the concentric peak powers documented in Figure 2, only one participant had their peak power in the pinch protocol, while seven participants created their highest peak power in the lag protocol. The last four participants measured their highest peak power in the familiarization protocol.
Strict Eccentric Plots
Eccentric Peak Power with the Vest Harness
Two participants had their highest peak power in the familiarization protocol while the other ten participants were evenly distributed between the pinch and lag protocol for their highest peak power.
Eccentric Peak Power with the Hip Belt
Five participants, the majority in this case, experienced their highest peak power in the familiarization protocol. Four participants experienced their peak power in the lag protocol, while only three participants created their highest peak power in the pinch protocol.
Concentric and Eccentric Peak Power Difference in the Vest Harness
In the vest harness, we see that there is an even distribution for the familiar protocol, with six participants displaying negative differentials and six displaying positive differentials. For the pinch protocol, a similar distribution is seen with six for each sign. The final protocol, the lag protocol is the only one that is not split evenly, with five participants having negative differentials and seven displaying positive differentials.
Concentric and Eccentric Peak Power Difference in the Hip Harness
While wearing the hip belt, for the familiarization and lag protocols, seven participants created higher peak powers in the eccentric direction than the concentric direction, as noted by the negative difference. In the pinch protocol, only six participants had negative differentials.
Concentric Peak Power Difference Between the Vest and Hip Harnesses
Four participants had negative power differentials for the familiarization peak power, three had negative power differentials for the pinch peak power and three had negative power differentials for the lag peak powers.
Eccentric Peak Power Difference Between the Vest and Hip Harnesses
The familiarization peak power differentials were negative for five participants, while the pinch and lag peak power differentials were each negative for only four participants.
Stay tuned for the final installment of this series where I’ll discuss the findings of this data.