1. Justin Hopkins
Chase Hunt-Murray
Christopher Johnston
Ereka Lambe
Title: The Effects of Heel Lift Height on Back Squat Performance
Introduction
Importance and Procedure of the Back Squat
The back-squat is a multi-joint movement used to develop neuromuscular control and
strength in both an athletic and rehabilitation setting in order to develop the posterior chain and
strengthen the muscles around the joints of the lower extremities (Myer et. al. 2014). Varying
techniques and athletic equipment is commonly used while performing a back squat in attempt
to achieve movement that will improve physical performance and decrease risk of training
related injuries (Myer et. al. 2014). The NSCA standard for the squat starts by having the
individual stand with their feet a comfortable width apart and flat on the floor, and with their body
in an upright position with all lower body joints extended. The descent phase of the squat begins
with a rigid and upright torso, with flexion at the ankle, knee, and hip joints. The descent phase
is complete when the thigh segment is parallel to the floor and the hip joint is at equal or lesser
height than the knee joint. The ascending phase begins with extension of the ankle, knee, and
hip joints. The ascending phase concludes when the participant has moved into a fully upright
position (Meyer et. al. 2014).
Back Squat and Weightlifting Shoes
Previous research has indicated different footwear may affect trunk lean, ankle
dorsiflexion, anterior knee displacement, and peak forces during the performance of a back
squat. Using an elevated-heel weightlifting shoe allows athletes to maintain a more upright trunk
position while keeping their knees in line with their toes without limiting ankle dorsiflexion (John
W. 2016). Ground reaction force studies have demonstrated that shoe cushioning systems can

2. cause variable effects on peak forces during knee flexion. Compared to a running shoe,
weightlifting shoes allowed the subject to successfully complete a squat with a significant
decrease in trunk lean and horizontal displacement. (Sato et al. 2013, Whitting et al. 2016). A
study comparing squat performance of athletes in barefoot, barefoot style shoes, running shoes,
and weightlifting shoe conditions, found that peak angle and relative range of motion were
significantly greater in in the running and weightlifting shoe condition compared to the barefoot
condition (Escamilla et al. 2001). These significant findings verify the presence of biomechanical
differences while squatting in several athletic shoe conditions. To our knowledge, there is little
previous literature on the effects of heel lift height within shoes studied during squat
performance. The current study will look further into how varying heel lift heights of the foot will
affect the athletic performance and technique during the back squat.
Specific Hypotheses
 Squatting with a heel height greater than 1.9cm will increase power output as well as
decrease ankle dorsiflexion and overall forward trunk lean.
 Squatting with a heel height less than 1.9cm with reduce power output, decrease ankle
dorsiflexion, and increase forward trunk lean.
Methods
Participants
One male participant was chosen at convenience. The subject has at least five years of
experience squatting. The participant is 1.75m tall, weighs 79.5 kg and 22 years old. Force plate
weight is 785.9 Newtons. Participant 1RM is 129 kg and the 70% weight used was 90.9 kg.
There were no performance limitations due to previous injury.
Experimental Set-Up
One 60hz camera was placed in the sagittal plane of the squatter in order to record motion used
to create a 2D figure. Reflective markers were placed at the 5th metatarsal joint, lateral femoral
epicondyle, and greater trochanter of the right side of the body (Sato et al. 2012). A marker was

3. also placed on the end of the of the bar to represent the shoulder. Trunk, thigh, shank, and foot
segments were obtained from the placement of the markers (Sato et al. 2012). Vicon Motus
version 10.1 was used to analyze the video data. One force plate was used for each the left and
the right foot. The data from the force plates were merged to obtain power. Changes of heel
height came from wooden wedge heights of 0.64 cm, 1.27 cm, 2.54 cm, 3.18 cm. A total of five
trials were done at each wedge height and barefoot condition. Each trial included five back-
squat repetitions.
Data Collection
Prior to testing the participant performed a 10-minute dynamic warm up. After the warm
up, the participant stood on the force plates to obtain their weight in newtons and for force plate
calibration. Each foot was on a different force plate. There were a total of five trials. The
participant stood on the force platforms and performed 5 squat repetitions at 70% of the
participant 1RM. The trials started with the barefoot squat then increased to the next
subsequent wedge height (0.64 cm, 1.27 cm, 2.54 cm, 3.18 cm). The participant rested 5
minutes in between each trial to avoid fatigue factors that could compromise technique.
Data Analysis
In order to calculate anterior knee displacement, the average highest position of the
knee in the X (A-P) direction was first obtained. To obtain this value (X knee high), the height of
the knee at the start of the squat was averaged from the middle three repetitions. This value
was then subtracted from the average lowest position of the knee in the X (A-P) direction. To
obtain this value (X knee low) the height of the knee at the lowest part of the squat was average
from the middle three repetitions. The equation (X knee low – X knee high) was done for all five
trials in order to obtain anterior knee displacement for each trial. In order to calculate anterior
trunk displacement (trunk lean), the average highest position of the shoulder in the X (A-P)
direction was first obtained. To obtain this value (X shoulder high), the height of the shoulder at
the start of the squat was averaged from the middle three repetitions. This value was then

4. subtracted from the average lowest position of the shoulder in the X (A-P) direction. To obtain
this value (X shoulder low) the height of the shoulder at the lowest part of the squat was
average from the middle three repetitions. The equation (X shoulder low – X shoulder high) was
done for all five trials in order to obtain trunk lean for each trial.
Results
Slight differences in anterior knee displacement we found between the trials. Anterior Trunk
displacement varied for all five trials. As the heel height increased, ankle range of motion
decreased and peak ankle flexion
increased. Heel height and power
increased in a linear fashion. Highest
power output was seen at heel
heights 0.64 cm and
2.54 cm, with 2.54 cm being the
highest at 1,639 Newtons. Trial
number 5 was not used in power
output comparison due to faulty
force plate reading.
Discussion
Previous literature states
biomechanical deficits including
poor ankle mobility and hip
flexibility amplify compressive and
shear forces within the lumbar
spine due to increased anterior
displacement of the trunk
(Whitting et al. 2016). Data
Trial Anterior Trunk
Displacement
(meters)
Anterior Knee
Displacement
(meters)
Ankle
RoM
(degrees)
Peak
Ankle
Flexion
(degrees)
1.1 (Barefoot) 0.055 0.111
2.1 (0.64cm) 0.061 0.111
3.1 (1.27cm) 0.043 0.111
4.1 (2.54cm) 0.041 0.0983
5.1 (3.18cm 0.048 0.092
Figure 1: Power outputs for trials 1-4
Table 1: Measured kinematic variables

5. collected from the current study found that the most trunk displacement occurred at a heel
height of 0.64 cm. All other heel height trails had similar amounts of trunk displacement. This
indicates that when buying a weightlifting shoe, a shoe with a heel raise greater than .64cm
should be chosen in order to minimize trunk lean, thus reducing the chance of lumbar spine
injury. The data also determined increasing heel height during squat performance reduces trunk
lean once above the 0.64cm specific heel height. As the heel height increased, no significant
changes were seen in anterior knee displacement. Anterior movement of the knees is found to
increase the amount of shear stress on the knee joint (Fry, Smith, & Schilling, 2003).
Weightlifting shoe heel height did not significantly affect anterior knee movement. This indicates
that people with knee issues will not have problems squatting with weightlifting shoes, due to
their ability to improve performance while keeping shear stress consistent in the knees and
lower back. The lack of anterior-posterior displacement in our study can be attributed to
personal technique (Comfort & Kasim, 2007) as well as small sample size. Increases in peak
ankle flexion indicates more vertical shank position consistent with proper squat technique
teachings (Chandler & Stone, 1991). A more vertical shank position when wearing weightlifting
shoe is indicative of minimal anterior knee movement which reduces stress in the knee. As
seen in our data, peak ankle flexion increased as the heel height increased. Limited differences
seen in the ankle range of motion between weightlifting shoes and running shoes is likely due to
the direct effect of the raised heel seen in weightlifting shoes. During the squatting performance,
the knees are then able to move slightly over the toes, which has been revealed through
previous research as an effective way to minimize hip and knee joint torque (Fry, Smith, &
Schilling, 2003).
One limitation of the current study is that an inadequate number of trials available for
comparing the tested heel heights to the heel height of an actual weightlifting shoe (1.9cm). Trial
number 5.1, with a heel height of 3.18 cm was examined and determined void, limiting the
number of trials available for analysis in peak power outputs. If both heel heights of 1.9cm and

6. 3.18cm had been tested, conclusions seeking the optimal heel height for maximum power
output could be determined. Another limitation relates to the use of bare feet on wooden
wedges instead of using actual weightlifting shoes with different heel heights. This may cause
an inaccurate real-world comparison of power output, knee displacement, and trunk lean
displacement between. Other research notes additional components of weightlifting shoes that
provide benefits including having a strap and sole within the weightlifting shoe (Fredrick E.
1986). The current study used one male subject to examine individual differences of squat
performance in varied heel lift conditions, which limits the relevance of our findings across
multiple populations.

7. References
Bae, C. H., Jeong, Y. W., & Lee, J. H. (2015). Analysis of muscle activations in lower extremities
muscles at various angles of ankle flexion using wedges during static squat exercise.
Journal of physical therapy science, 27(9), 2853.
Chandler, T. J., & Stone, M. H. (1991). The squat exercise in athletic conditioning: A position
statement and review of literature. Strength and Conditioning Journal, 13(5), 51-60.
Comfort, P., & Kasim, P. (2007). Optimizing Squat Technique. Strength & Conditioning Journal
(Allen Press), 29(6), 10-13.
Escamilla, R., Fleisig, G., Zheng, N., Lander, J., Barrentine, S., Andrews, J., Bergemann, J. W.,
& Moorman III, C. (2001). Effects of technique variations on knee biomechanics during
the squat and leg press. Medicine & Science In Sports & Exercise, 33(9), 1552-1566.
Fortenbaugh, D., Sato, K., & Hitt, J. (2010). The effects of weightlifting shoes on squat
kinematics. ISBS-Conference Proceedings Archive (Vol. 1, No. 1).
Frederick, E. C. (1986). Kinematically mediated effects of sport shoe design: A review. Journal
of Sports Sciences, 4(3), 169-184.
Fry, A. C., Smith, J. C., & Schilling, B. K. (2003). Effect of Knee Position on Hip and Knee
Torques During the Barbell Squat. Journal Of Strength And Conditioning Research, 17,
629-633.
Myer, G. D., Kushner, A. M., Brent, J. L., Schoenfeld, B. J., Hugentobler, J., Lloyd, R. S., &
McGill, S. M. (2014). The Back Squat: A Proposed Assessment of Functional Deficits
and Technical Factors That Limit Performance. Strength & Conditioning Journal, 36(6),
4-27.
Sato, K., Fortenbaugh, D., & Hydock, D. S. (2012). Kinematic Changes Using Weightlifting
Shoes on Barbell Back Squat. Journal Of Strength & Conditioning Research, 26(1), 28.

8. Sato, K., Fortenbaugh, D., Hydock, D., & Heise, G. (2013). Comparison of back squat
kinematics between barefoot and shoe conditions. International Journal of Sports
Science and Coaching, 8(3), 571-578.
Vázquez-Guerrero, J., Moras, G., Baeza, J., & Rodríguez-Jiménez, S. (2016). Force Output
during Squats Performed Using a Rotational Inertia Device under Stable versus
Unstable Conditions with Different Loads. Plos ONE, 11(4), 1-13. doi:10.1371/0154346
Whitting, J., Meir, R., Crowley-Mchatton, Z., & Holding, R. (2016). Influence of Footwear Type
on Barbell Back Squat Using 50, 70, and 90% of One Repetition Maximum a
Biomechanical Analysis. Journal Of Strength & Conditioning Research, 30(4), 1085-
1092.