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Shod versus barefoot effects on force and power development during a conventional deadlift

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The kinetics of a conventional deadlift in shod (S) versus unshod (US) footwear conditions in 10 male participants (mean ± SD, age = 27.0 ± 5.8 years; weight = 78.7 ± 11.5 kg; height = 175.8 ± 8.2 cm; 1RM deadlift = 155.8 ± 25.8 kg) was assessed in two testing sessions. A counterbalanced, crossover experimental design was used with different loads (60% and 80% 1RM). Four sets of four repetitions were prescribed per session with two sets per shoe and with each shoe condition involving one set per load. Peak vertical force (PF), rate of force development (RFD), time to peak force (TPF), anterior-posterior (COP-AP) and medio-lateral (COP-ML) center of pressure excursion, and barbell peak power (PP) data were recorded during all repetitions. Except for RFD (F = 6.389; p = 0.045; ηp = 0.516) and ML-COP (F = 6.696; p = 0.041; ηp = 0.527), there were no other significant main effects of shoe. There were significant main effects of load for PF (p < 0.05), COP-AP (p = 0.011), TPF (p = 0.018) and COP-AP (p = 0.011). There were no significant interactions found between session, shoe and load (p range from 0.944 to 0.086). While the unshod condition may have produced changes in RFD and ML-COP compared with the shod condition, there is only limited evidence in the current study to support this lifting technique for the conventional deadlift. Further investigation is required to clarify any possible implications of this result and its benefit to lifters.
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JSCR-08-9072-R1
Accepted for publication September 2017
Shod versus barefoot effects on force and power
development during a conventional deadlift
Word count = 3,361
Abstract = 250/250
Figures x 3
Tables x 1
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ABSTRACT
The kinetics of a conventional deadlift in shod (S) versus unshod (US) footwear conditions in 10 male
participants (mean ± SD, age = 27.0 ± 5.8 years; weight = 78.7 ± 11.5 kg; height = 175.8 ± 8.2 cm; 1RM
deadlift = 155.8 ± 25.8 kg) was assessed in two testing sessions. A counterbalanced, crossover
experimental design was used with different loads (60% and 80% 1RM). Four sets of four repetitions
were prescribed per session with two sets per shoe and with each shoe condition involving one set per
load. Peak vertical force (PF), rate of force development (RFD), time to peak force (TPF), anterior-
posterior (COP-AP) and medio-lateral (COP-ML) center of pressure excursion, and barbell peak power
(PP) data were recorded during all repetitions. Except for RFD (F = 6.389; p = 0.045; ƞp2 = 0.516) and
ML-COP (F = 6.696; p = 0.041; ƞp2 = 0.527), there were no other significant main effects of shoe. There
were significant main effects of load for PF (p < 0.05), COP-AP (p = 0.011), TPF (p = 0.018) and COP-
AP (p = 0.011). There were no significant interactions found between session, shoe and load (p range
from 0.944 to 0.086). While the unshod condition may have produced changes in RFD and ML-COP
compared with the shod condition, there is only limited evidence in the current study to support this
lifting technique for the conventional deadlift. Further investigation is required to clarify any possible
implications of this result and its benefit to lifters.
Word count: 250/250
Keywords: lifting technique, force production, footwear
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INTRODUCTION
The deadlift is a closed chain, multi-joint resistance exercise that involves moving a stationary barbell
from the floor until extension is established at the hips and knees. Within the strength and conditioning
fields, the deadlift is seen as an important part of an athletic training program for the development of
strength and power in the posterior chain i.e. back, hips and hamstrings (9, 30, 31, 35). In Powerlifting
competitions, the deadlift is the final of three contested lifts and is essential in developing a competitive
total weight lifted (15). In the rehabilitation community, the deadlift and its variations are a common
protocol in the post-operative and non-operative rehabilitation of the lower back, anterior cruciate
ligament (ACL) and hamstrings (24).
As with the squat, there is debate among weightlifting equipment forums about the best shoes to wear
while deadlifting. Strength and conditioning researchers, and a range of industry practitioners (e.g. 6, 8,
13, 18, 19), have stated that weightlifting shoes, non-compressive soled shoes, or unshod (socks only or
barefoot) conditions are essential in providing a stable platform and effective force transfer from the
ground to the bar. In contrast, it could be argued that soft soled shoes, such as traditional running shoes,
delay force transmission and create instability, altering the direction of the resultant ground reaction force
(GRF), thus compromising lifting performance.
There appears to be no research published on how different footwear affect the kinetics or kinematics of
the deadlift. However, with respect to the barbell back squat Shorter et al. (28) found that when using
loads at 80% of 1RM shod lifters wearing lower profile, soft sole training shoe produced higher peak
power and peak GRF than lifters wearing minimalist shoes or no shoes. Furthermore, Shorter et al. (28)
found that the shod condition displayed a larger excursion in the center of pressure (COP) than the
minimalist or no shoe conditions. Interestingly however, research conducted by Whitting et al. (34)
reported a significantly larger anterior-posterior COP excursion during the barbell back squat for
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participants wearing a solid, rear-foot elevated weightlifting shoe when compared to a standard sports
shoe. Although one might reasonably surmise that the stable weightlifting shoe could elicit similar effects
in COP excursion to minimalist or barefoot conditions, it seems that the findings of these two studies are
at odds with one another. Further research comparing a shod condition with an unshod condition in the
barbell back squat has not provided kinetic data to help elucidate this small body of research (13, 25). As
a result, it appears that shoe effects on kinetic parameters in common weightlifting modes remains poorly
understood.
The deadlift and its variations have been studied extensively, with a number of biomechanical analyses of
the deadlift reported in the literature (3, 30, 31). Several studies have focused on joint and segment angles
in deadlift variations (26, 33), with two studies specifically focused on the comparison of kinematics and
kinetics of the sumo deadlift and the conventional deadlift (9, 11). Further research has been completed
on muscle activation patterns via electromyography in both stable and unstable conditions (5, 10, 17, 23).
However, none of the aforementioned studies made reference to the types of footwear worn during testing
conditions, and nor was COP data provided.
Research (15) has also found that there are significant kinematic differences between the back squat and
deadlift, indicating that the data compiled for the squat may not be entirely relevant for the deadlift.
Therefore, given current and yet to be supported beliefs that deadlifting performance may be enhanced by
wearing minimalist shoes or by being barefoot, it was the purpose of this study to determine possible
kinetic effects of different footwear conditions (shod and unshod) while performing a conventional
deadlift. Specifically, this study aimed to determine whether the peak vertical ground reaction force (PF),
peak vertical power (PP), rate of force development of the peak force (RFD), time to peak force (TPF),
and center of pressure excursions in the anterior-posterior axis (COP-AP) and medio-lateral axis (COP-
ML) were affected by these shoe conditions. It was hypothesized that a deadlift in an unshod condition
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would provide a higher magnitude of PF, PP, RFD and a reduced COP excursion on the ML and AP axis
when compared to a shod condition.
METHODS
Experimental Approach to the Problem
A within-subject, counter-balanced, crossover experimental design was used to quantify the impact of the
two lifting conditions (S = shod in regular training shoes, US = Unshod) on the kinetics of the
conventional deadlift at different %1RM loads. Data was collected for each participant over 3 sessions
(initial 1RM testing and 2 trial sessions), each separated by a minimum of 72 hours to avoid any possible
influence of fatigue. All sessions were conducted at the institutional biomechanics laboratory. During the
trial sessions, participants completed 4 repetitions of the conventional deadlift with pronated grip using
60 and 80% of their predetermined 1RM. A total of 4 sets were completed on each of the 2 trial sessions.
All lifts were completed in both shod and unshod conditions with the order of footwear condition
reversed for the second testing session. Participants were required to wear those shoes that they normally
wore (all soft soled “trainers”) during training in the shod condition, and to be barefoot in the unshod
condition.
Subjects
A total of 10 male participants (group mean ±SD: age = 27.0 ± 5.8 years, age range = 20-33 years, weight
= 78.7 ± 11.5 kg, height = 175.8 ± 8.2 cm and 1RM = 155.8 ± 25.8 kg) volunteered for this study. To be
eligible to participate, participants were required to have a minimum of 2 years training age using the
conventional deadlift and to have used maximal and near maximal loads in this lift as part of their normal
training program. Participants had to be free from injury and illness and complete a pre-screening
exercise and health questionnaire to identify any contraindications to their participation. Prior to agreeing
to their involvement participants were provided with an information sheet that described all aspects of the
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research, including any potential risks and benefits. Having agreed to participate each participant
attended a familiarization session where the test process was explained verbally and written informed
consent was obtained. At this session, each participant had their 1RM deadlift score established under the
supervision of an accredited Australian Weightlifting Federation coach. Participants were instructed to
avoid both caffeine and lifting maximal loads in the 24 hours immediately prior to each data collection
session. Participants were randomly assigned to Group 1 (G1) or Group 2 (G2) to determine the ordering
of their first shoe test condition (S or US respectively) in their first testing session. All participants
reversed the order of shoe condition during their second session to control the potential effect of shoe
order on the kinetic outcomes. All procedures used in this research were approved by the Southern Cross
University Human Research Ethics committee (ECN-16-072) and complied with the Declaration of
Helsinki.
Procedures
Establishing deadlift 1RM
Upon agreeing to participate, baseline measurements (age, height and weight) were recorded for each
participant. Participants then performed a standardized warm-up of approximately 8 minutes that
comprised of 2 minutes on a Monarch cycle ergometer (utilizing a low load while maintaining a cadence
of ~70-80 rpm), and a series of prescribed dynamic stretches. Participants were then tested for their
deadlift 1RM wearing their normal training shoes. Deadlift technique was visually assessed by an
accredited Australian Weightlifting Federation coach prior to establishing their 1RM. Participants
performed the following conventional deadlift sequence to attain their 1RM: i) 5-10 repetitions on a 20kg
bar; followed by time to load the bar; ii) 4-5 repetitions at 70kg (approximately 40-60% of predicted
1RM) followed by 3 minutes rest; iii) 1 repetition at 70-80% of predicted 1RM followed by 3 minutes
rest; iv) 1 repetition at approximately 90% of their predicted 1RM followed by a minimum of 3 minutes
rest. Participants were then given six attempts to reach their 1RM with a minimum of 3 minutes rest
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between attempts as established in previous protocols (4, 13, 17, 20). The final 1RM was considered as
the load successfully lifted immediately prior to the failed attempted load. A successful lift was
considered as observation of full extension of the hip and knee. Chalk was the only supportive aid used to
prevent hands from slipping on the bar due to sweat.
Deadlift trial conditions
On Arrival for session 2, participants performed the standardized warm-up and then performed the
following deadlift sequence: i) 5-10 repetitions with a 20kg bar; followed by time to load bar; ii) 5-6
repetitions at 50% of their first experimental load (i.e. approx. 30% of 1RM) followed by 1 minute rest;
iii) 4 repetitions at 60% of 1RM followed by 3 minutes rest; iv) 4 repetitions at 80% of 1RM followed by
5 minutes rest. Following this rest period, participants completed the lifting sequence as identified in
points iii-iv above, in the second experimental condition. All deadlifts were performed as a conventional
deadlift with both hands pronated. No feedback was given during data capture; however, prior to lifting,
all participants were instructed to perform the concentric phase of the lift as fast as possible.
GRF data were sampled (1000Hz) for each trial as participants stood with both feet on a single Kistler
force plate (Type 9287; Winterthur, Switzerland) using Nexus software (version 1.8.4, 2013). GRF were
filtered (ƒc = 100 Hz) with a Butterworth fourth-order low-pass filter. Filtered data were used to calculate
the PF, RFD and COP excursions in the anterior-posterior (AP) and mediolateral (ML) directions. Data
for PP were collected using a Gym Aware Power Tool 5 (Kinetic Performance Technology, Canberra,
Australia) as seen in Figure. 1. All variables of interest were determined from data extracted from the
concentric phase of the lift, corresponding to the period of time where force and power is developed
during the lift.
Insert Figure 1 about here
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Statistical Analysis
A three-factor (session x shoe x load) repeated-measures ANOVA was used to determine whether there
were main effects of session, shoe condition (S and US) or load (60 and 80% 1RM), and whether there
were any interactions (session x shoe, session x load, session x shoe x load, shoe x load). Upon
identification of significant effects, post-hoc analyses with a Bonferroni adjustment were used to
minimize the chance of type I errors. Processed data were identified and entered into an Excel spreadsheet
for the development of all descriptive values. A priori sample size calculation using G*Power with an α
level of 0.05, and a power of 0.8, indicated that a sample size of 8 was sufficient for statistical analysis.
All statistical analyses were conducted using SPSS version 20 for Windows with an α level set at 0.05.
Effect size interpretation was in accordance with Cohen (7), which states that for partial eta squared a
small effect is 0.01 0.059, medium effect is 0.06 0.139 and large is 0.14 and above.
RESULTS
Means and standard deviations (±SD) for all variables are displayed in Table. 1. Shoe condition main
effects were found to be significant for RFD (F = 6.389; p = 0.045; ƞp2 = 0.516) and ML-COP (F = 6.696;
p = 0.041; ƞp2 = 0.527), with post-hoc comparisons indicating the unshod condition producing a greater
rate of force development (Figure. 2) and lower ML-COP displacements (Figure. 3) than the shod
condition respectively. Non-significant shoe effects were found for PF, TPF, PP, or AP-COP (F range
from 0.270 to 4.567; p range from 0.618 to 0.076). No significant main effects of session (F range from
0.103 to 2.861; p range from 0.758 to 0.142) were found for any of the independent variables. Main
effects of load were significant for PF (F = 83.090; p < 0.05; ƞp2 = 0.912), TPF (F = 9.411; p = 0.018; ƞp2
= 0.573), and COP-AP (F = 10.914; p = 0.011; ƞp2 = 0.577), with pair-wise post-hoc comparisons
indicating a significant increase in these variables at 80% compared to 60% of 1RM. No significant main
effects of load were found for PP (F = 0.005; p = 0.944; ƞp2 < 0.05), RFD (F = 3.632; p = 0.105; ƞp2 =
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0.377), or COP-ML (F = 4.055; p = 0.091; ƞp2 = 0.403). There were no significant interactions found
between session, shoe and load (F range from < 0.05 4.222; p range from 0.944 to 0.086).
Insert Table 1 and Figures 2 & 3 about here
DISCUSSION
The purpose of this study was to determine possible kinetic effects of different footwear conditions (shod
versus unshod) while performing a conventional deadlift; specifically during the concentric phase of the
lift using submaximal training loads. Biomechanical effects of the deadlift exercise have been studied
extensively (1, 2, 4, 9-11, 15, 16, 25, 30, 31). However, to the best of our knowledge there has been no
research published with reference to the kinetic effects of shod or unshod conditions during this exercise.
Data analysis showed significant main effects of shoe on RFD and ML-COP; with unshod lifters able to
apply more force to the floor at a faster rate. RFD was assessed as one of the main variables to investigate
anecdotal beliefs in the strength and conditioning community that there is a perceived ‘disconnect’
between the ground and the feet in a soft soled shoe (8, 12, 18, 19). This lifting strategy is based on an
assumption that the soft sole in these shoes is likely to produce instability, since the shoe sole must be
compressed before any effective force transfer can occur between the ground and the feet. The extension
of this belief is that an impeded force transmission will result in a delayed and reduced vertical GRF,
thereby compromising lifting performance. Upon initial analysis of the data in the present study, a
significantly higher RFD in the unshod compared to shod condition lends some weight to these anecdotal
comments. However, this finding needs to be viewed with caution for a number of reasons. Firstly, the
statistical strength appears weak to moderate (p = 0.045; ƞp2 = 0.516; observed power = 0.563).
Secondly, given Figure 2, it is questionable as to whether the means (±SE) of each data set are
functionally different. Lastly, and perhaps most importantly, there were no shoe x load interactions, and
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no other significant main effects of shoe for the other primary indicators of power and force output (PP
and PF). As such, this study does not provide substantive evidence to support the hypotheses developed to
prove current anecdote and practice i.e. that there is an advantage for producing force and power when
deadlifting unshod.
It should also be noted, that kinematic data were not collected during the present study. As a result, it
could not be determined whether compression of the shoe sole might be a factor correlated with a
possibly slower RFD in the shod condition. Furthermore, with TPF only significantly different in main
effects of load, it would appear that the duration of the concentric phase of the deadlift may be unaffected
by shoe condition, and that any possible delay in GRF at the start of the lift may have been overcome
during the concentric phase. Future biomechanical investigations of the deadlift, concerning different
footwear conditions, should collect kinematic data to determine any possible links between performer and
shoe movements, and kinetic outputs such as RFD.
As expected, peak vertical ground reaction forces (PF) were found to significantly differ between the load
conditions. Post-hoc analyses indicates a greater magnitude of peak force at 80% of 1RM than at 60% of
1RM, thereby confirming the results of previous studies (2, 4, 30, 33). Peak power was similar between
loads of 60% and 80% of 1RM, respectively. Previous studies that focused on PF, velocity and PP (2, 4,
30) for the deadlift and upper body (29), have reported a larger magnitude of power at 60% than at 80%
of 1RM. Power, being a product of force and velocity (P = F.V) (15, 26, 33) may be generated more
easily with submaximal resistance from lighter loads, predominantly due to substantially greater
velocities, despite slightly lower peak forces. While not reported, velocity data taken from the Gym
Aware showed a 20% increase in bar velocity at 60% of 1RM compared to loads lifted at 80% of 1RM,
while GRF data showed a 9% increase in PF when lifting at 80% of 1RM. These values show a somewhat
proportional increase in force to the decrease in velocity, thereby explaining the similarity in our absolute
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PP values. While we are unable to confirm the cause of the discrepancy in our PP data when compared to
the previously mentioned studies, the majority of participants noted several grip issues with the pronated
grip, which was standardized in this analysis. A majority of the lifters in this study performed the deadlift
with an alternating grip during training sessions, and so it is speculated that this may have had an effect
on lift velocity.
The control of bipedal stance involves the complex integration of sensory inputs, perceptual processing of
those inputs, and the production of appropriate motor commands in response (22). The measurement of
the COP trajectory changes during the deadlift in the current study showed that COP-AP displayed
significant main effects of load, and COP-ML showed an effect of shoe. Post-hoc analyses of COP-AP
indicated larger COP displacement at 80% versus 60% of 1RM while the COP-ML exhibited larger COP
displacements when shod versus unshod. This suggests that the motor control systems appears to alter
independently the motor behavior of the postural control system when experiencing changes in either load
or surface conditions. To our knowledge however, this is the first study to investigate COP excursions in
the deadlift and the potential effect of differing loads and shod conditions on COP behaviour, and
therefore direct comparisons of findings is difficult.
One possible way to interpret these findings could be to explain the results through the Equilibrium Point
(EP) hypothesis. This hypothesis states that the central nervous system (CNS) initiates and modifies
movement by using sensory input to shift the equilibrium states of the motor system (21). Since the motor
control system controls the COP movement and directs it towards steady state behaviors, under heavier
loads or more compliant plantar surface conditions, the motor system may be achieving its final planned
behaviour through flexibility in its control strategies and hence leading to larger COP movements.
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Tahayori et al. (32) investigated the effects of differential loading on the COP behaviour in quiet stance
and found that a load equal to 15% of body mass to the back of the torso was effective in increasing COP
movement, especially in the ML direction. Interestingly, the application of the same load to the front of
the torso led to no change in COP movement behaviour, which is contrary to the COP changes found in
the current study during dynamic frontal loading (i.e. the deadlift). These differences may be the result of
the considerable methodological differences between the studies, including static v dynamic actions and
relatively low loads v relatively high loads. Therefore it is suggested that further research be undertaken
to elucidate the potential mechanism of the changes in COP behavior with differing loads.
The deadlift is performed with a variety of techniques (e.g. sumo, clean deadlift, snatch deadlift,
alternating grip) and with a variety of assistive equipment, such as straps, belts and deadlifting suits. As
such, limiting preferred technique and assistance equipment may influence an individual’s deadlifting
performance, which may explain large variances between subjects in this and other studies.
PRACTICAL APPLICATION
This study was developed from an observed practice within the strength and conditioning field regarding
possible or perceived effects of different footwear on performance during the conventional deadlift.
Motives for the participation in the deadlift vary and it is performed using a variety of techniques. Thus it
is essential that rehabilitation and strength and conditioning practitioners employ evidence-based
practices to reduce the chance of injury and to provide optimal outcomes. The findings of this current
investigation do not provide strong support for the practice, by some sections of the strength and
conditioning community, of being unshod during the deadlift exercise as a strategy for significantly
improving deadlifting performance.
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Table 1: Mean (±SD) of recorded variables displayed for each shoe (S, US) and load (60 and 80% 1RM) condition (N = 10).
60% 1RM
80% 1RM
S
US
US
Average PF (N)†
2060.1 (236.4)
2072.4 (240.5)
2257.4 (289.0)
Average PP (W)
1129.0 (142.5)
1135.5 (148.4)
1117.7 (75.2)
Average RFD (N/s)‡
1840.4 (794.2)
2099.7 (915.9)
2008.1 (772.3)
Average TPF (s)†
0.5 (0.3)
0.5 (0.2)
0.6 (0.3)
Average COP-AP (mm)
41.7 (13.6)
45.6 (16.4)
56.4 (22.0)
Average COP-ML (mm)§
18.8 (7.0)
15.8 (7.2)
18.6 (5.4)
1RM = 1 repetition maximum; S = Shod; US = Unshod; COP = center of pressure; AP = anterior-posterior; ML = medio-lateral.
Indicates a main effect of load post-hoc comparison showing larger magnitude of PF, TPF and COP-AP.
Indicates main effect of shoe condition post-hoc comparison indicating faster RFD for unshod v shod conditions.
§ Indicates main effect of shoe condition post-hoc comparison indicating greater COP excursion with shod v unshod conditions
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Figure 1: Placement of Gym Aware Power Tool 5 and position of participant on force plate.
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Figure 2: Mean (± SE) shoe main effects for rate of force development (N.s-1) between shod (S) and
unshod (US) conditions. * Indicates significantly higher RFD in the US condition (P = 0.045).
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Figure 3: Mean (± SE) shoe main effects for medio-lateral (ML) peak center of pressure (COP)
displacement (mm) between shod (S) and unshod (US) conditions. * Indicates significantly greater
displacement in the shod condition (P < 0.041).
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REFERENCES
1. Bird, SPC and Barrington-Higgs, B. Exploring the deadlift. Strength Cond J, 32: 46-51, 2010.
2. Blatnik, JA, Goodman, CL, Capps, CR, Awelewa, OO, Triplett, TN, Erickson, TM, and McBride,
JM. Effect of load on peak power of the bar, body and system during the deadlift. J Sports Sci
Med, 13: 511-515, 2014.
3. Brown, EW and Abani, K. Kinematics and kinetics of the deadlift in adolescent power lifters. Med
Sci Sports Exerc, 17: 554-566, 1985.
4. Camara, K, Coburn, J, Dunnick, D, Brown, L, Galpin, A, and Costa, P. An examination of muscle
activation and power characteristics while performing the deadlift exercise with straight and
hexagonal barbells. J Strength Cond Res, 30: 1183-1188, 2016.
5. Chulvi-Medrano, I, Garcia-Masso, X, Colado, J, Pablos, C, de Moraes, J, and Fuster, M. Deadlift
muscle force and activation understable and unstable conditions. J Strength Cond Res, 24: 2723-
2730, 2010.
6. Clay, H. Go barefoot to get stronger. 2009. https://www.t-nation.com/training/go-barefoot-to-get-
stronger. Accessed 11 Feb/2016.
7. Cohen, J. Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale, NJ: Lawrence
Erlbaum Associates, 1998, pp. 1-17.
8. Cormie, P, McBride, JM, and McCaulley, GO. Power-time, force-time, and velocity-time curve
analysis during the jump squat: Impact of load. J Appl Biomech, 24: 112-120, 2008.
9. Cressey, E. Maximum strength FAQ. 2008. http://ericcressey.com/maxstrengthfaqhtml. Accessed
11 Feb/2016.
10. Escamilla, RF, Francisco, AC, Fleisig, GS, Barrentine, SW, Welch, CM, Kayes, AV, Speer, KP,
and Andrews, JR. A three-dimensional biomechanical analysis of sumo and conventional style
deadlifts. Med Sci Sports and Exercise, 32: 1265-1275, 2000.
11. Escamilla, RF, Francisco, AC, Kayes, AV, Speer, KP, and Moorman, CT. An eletromyographic
analysis of sumo and conventional style deadlifts. Med Sci Sports and Exercise, 34: 682-688,
2002.
12. Escamilla, RF, Lowry, TM, Osbahr, DC, and Speer, KP. Biomechanical analysis of the deadlift
during the 1999 Special Olymics World Games. Med Sci Sports and Exercise, 33: 1345-1353,
2001.
13. Everett, G. Olympic weightlifting: A complete guide for athletes and coaches. Calif.: Catalyst
Athletics, LLC, 2012, p. 22.
14. Fortenbaugh, D, Sato, K, and Hitt, JK. The effects of weightlifting shoes on squat kinematics.
Presented at Proceeding of the XXVIII International Symposium on Biomechanics in Sport,
Northern Michigan University, Michigan, USA, pp. 167-170, 2010.
18
15. Grimshaw, P, Lees, A, Fowler, N, and Burden, A. Sport and Exercise Biomechanics. New York,
NY: Taylor & Francis Group, 2007, pp. 211-218.
16. Hales, ME, Johnson, BF, and Johnson, JT. Kinematic analysis of the powerlifting style squat and
the conventional deadlift during competition: Is there a cross-over effect between lifts? J Strength
Cond Res, 23: 2574-2580, 2009.
17. Hales, MP. Improving the deadlift: Understanding biomechanical constraints and physiological
adaptations to resistance exercise. Strength Cond J, 32: 44-51, 2010.
18. Hamlyn, N, Behm, D, and Young, W. Trunk muscle activation during dynamic weight-training
exercises and isometric instability activities. J Strength Cond Res, 21, 2007.
19. Kawamoto, J. Sure-fire way to learn the clean. 2012. https://www.t-nation.com/training/sure-fire-
way-to-learn-the-clean. Accessed 11 Feb/2016.
20. Kilgore, JL, and Rippetoe, CM. Weightlifting shoes 101. 2006.
http://www.exrx.net/WeightTraining/WeightliftingShoes.html. Accessed 11 Feb/2016.
21. Lafond, D, Duarte, M, and Prince, F. Comparison of three methods to estimate the center of mass
during balance assessment. J Biomech, 37: 1421-1426, 2004.
22. Latash, ML. Motor synergies and the equilibrium-point hypothesis. Motor Control, 14: 294-322,
2010.
23. Maurer, C, Mergner, T, and Peterka, RJ. Multisensory control of human upright stance. Exp Brain
res, 171: 231-250, 2006.
24. McAllister, MJ, Hammond, KG, Schilling, BK, Ferreria, LC, Reed, JP, and Weiss, LW. Muscle
activation during various hamstring exercises. J Strength Cond Res, 28: 1573, 2014.
25. Sato, K, Fortenbaugh, D, and Hydock, DS. Kinematic changes using weightlifting shoes on
barbell back squat. J Strength Cond Res, 26: 28-33, 2012.
26. Schellenberg, F, Lindforfer, J, Renate, L, William, TR, and Lorenzetti, S. Kinetic and kinematic
differences between deadlifts and goodmornings. BMC Sports, Sci Med Rehabil, 5: 27 (abstract),
2013.
27. Shorter, K, Lake, J, Smith, N, and Lauder, M. Influence of the foot-floor interface on squatting
performance. Portuguese J Sport Sci, 11: 385-388, 2011.
28. Soriano, MA, Jiménez-Reyes, P, Rhea, MR, and Marín, PJ. The optimal load for maximal power
production during lower-body resistance exercises: A meta-analysis. Sports Med, 45: 1191-1205,
2015.
29. Sreckovic, S, Cuk, I, Djuric, S, Nedeljkovic, A, Mirkov, D, and Jaric, S. Evaluation of force-
velocity and power-velocity relationship of arm muscles. Eur Appli Physiol, 115: 1779-1787,
2015.
19
30. Swinton, PA, Stewart, A, Agouris, I, Keogh, JWL, and Lloyd, R. A biomechanical analysis of
straight and hexagonal barbell deadlifts using submaximal loads. J Strength Cond Res, 25: 2000,
2011.
31. Swinton, PA, Stewart, AD, Keogh, JWL, Agouris, I, and Lloyd, R. Kinematic and kinetic analysis
of maximal velocity deadlifts performed with and without the inclusion of chain resistance. J
Strength Cond Res, 25: 3163, 2011.
32. Tahayori, B, Riley, ZA, Mahmoudian, A, Koceja, DM, and Hong, SL. Rambling and trembling in
esponse to body loading. Motor Control, 16: 144-157, 2012.
33. Thompson, BJ, Stock, MS, Shields, JE, Luera, MJ, Munayer, IK, Mota, JA, Carrillo, EC, and
Olinghouse, KD. Barbell deadlift training increases the rate of torque development and vertical
jump performance in novices. J Strength Cond Res, 29: 1, 2015.
34. Whitting, J, Meir, R, Holding, R, and Crowley-Mchattan, Z. Influence of footwear type on barbell
backsquat using 50, 70, and 90% of one repetition maximum: A biomechanical analysis. J
Strength Cond Res, 30: 1085-1092, 2015.
35. Winwood, PW, Cronin, JB, Brown, SR, and Keogh, JWL. A biomechanical analysis of the
farmers walk, and comparison with the deadlift and unloaded walk. Int J Sports Sci Coach, 9:
1127-1143, 2014.
... Despite the growing body of research comparing barefoot, shod, and different shoe designs on locomotion, research concerning the effect of footwear on resistance training performance from a biomechanical perspective is quite limited. A study by Hammer et al., 2018 found that the rate of force development was reduced when wearing shoes compared to barefoot, which lends some support that there is a dissociation between the shoe (i.e., the sole) and ground. The same study also found that the medio-lateral center of pressure excursion was significantly greater in the shoe condition [12], which suggests that footwear could have a consequential effect on frontal plane joint mechanics. ...
... A study by Hammer et al., 2018 found that the rate of force development was reduced when wearing shoes compared to barefoot, which lends some support that there is a dissociation between the shoe (i.e., the sole) and ground. The same study also found that the medio-lateral center of pressure excursion was significantly greater in the shoe condition [12], which suggests that footwear could have a consequential effect on frontal plane joint mechanics. However, contrasting research has shown increased antero-posterior excursion while barefoot in comparison to shod conditions, when assessing postural control [10]. ...
... While the reduction in center of pressure excursion may provide some support for barefoot training, Hammer et al., 2018 found no significance in peak force or in time to peak force between the footwear conditions. The author indicates that the time to complete the concentric phase of the lift is similar in both conditions as well [12]. While the time aspect may be similar, the displacement would likely be smaller, thereby reducing the velocity at which the movement is performed. ...
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Barefoot weightlifting has become a popular training modality in recent years due to anecdotal suggestions of improved performance. However, research to support these anecdotal claims is limited. Therefore, the purpose of this study was to assess the differences between the conventional deadlift (CD) and the sumo deadlift (SD) in barefoot and shod conditions. On day one, one-repetition maximums (1 RM) were assessed for thirty subjects in both the CD and SD styles. At least 72 h later, subjects returned to perform five repetitions in four different conditions (barefoot and shod for both CD and SD) at 70% 1 RM. A 2 × 2 (footwear × lifting style) MANOVA was used to assess differences between peak vertical ground reaction force (VGRF), total mechanical work (WORK), barbell vertical displacement (DISP), peak vertical velocity (PV) and lift time (TIME) during the concentric phase. The CD displayed significant increases in VGRF, DISP, WORK, and TIME over the SD. The shod condition displayed increased WORK, DISP, and TIME compared to the barefoot condition. This study suggests that lifting barefoot does not improve performance as no differences in VGRF or PV were evident. The presence of a shoe does appear to increase the DISP and WORK required to complete the lift, suggesting an increased work load is present while wearing shoes.
... T he deadlift is a compound, multiple-joint lower body exercise (1). Because the lift can be performed with heavy loads, a large mechanical stimulus is placed on the body, lending itself well to strength and power adaptations. ...
... The exercise can be relatively simple if properly taught and supervised. However, its simplicity does not diminish effectiveness of the exercise, making it an ideal movement to include in strength and conditioning programs and personal training sessions for lifters at all experience levels (1,4). In addition to its use in competitive athletics and recreational training, the deadlift is a valuable tool used in postoperative and nonsurgical rehabilitation protocols (1). ...
... However, its simplicity does not diminish effectiveness of the exercise, making it an ideal movement to include in strength and conditioning programs and personal training sessions for lifters at all experience levels (1,4). In addition to its use in competitive athletics and recreational training, the deadlift is a valuable tool used in postoperative and nonsurgical rehabilitation protocols (1). The exercise has been shown to be beneficial for reducing the risk of anterior cruciate ligament (ACL) injury and reducing low back pain (5). ...
... Although, it was found that B lifters had a greater rate of force development (Hammer et al 2018). ...
... A recent study has used the same sample size for similar testing and found significance in their data Price 9 (Hammer et al., 2018). Recruiting was carried out by opportunity sampling within the Plymouth area. ...
... There has been a large amount of research into the HBD, the conventional deadlift, the sumo deadlift and the squat on biomechanics with some research exploring footwear conditions and unstable surfaces. (Brown and Abani, 1985;Escamilla, 2001;Swinton et al., 2009;Chulvi-Medrano et al., 2010;Hales, 2010;Everett, 2012;Sato, Fortenbaugh and Hydock, 2012;Schilling, 2013;Legg et al., 2016;Hammer et al., 2018). However, there are no studies to date that have specifically investigated footwear conditions using isometric testing and a HB. ...
Thesis
Full-text available
Barefoot training effects on peak force and rate of force development
... The deadlift and its variations are widely accepted by strength and conditioning coaches as one of the "big three" exercises prescribed to develop total body strength, specifically the hip and knee extensors, spinal erectors, quadratus lumborum, core abdominal musculature, back, and forearm muscles (3). However, although there are several reports addressing correct teaching technique of the deadlift (3,12,15,17,27), the exercise has notoriously been loosely defined (15,27). Typically, the term "deadlift" is associated with 2 broad categories: the conventional deadlift (CD) and nonconventional styles (i.e., sumo) (3). ...
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This study compared the biomechanical characteristics of the farmers walk, deadlift and unloaded walk. Six experienced male strongman athletes performed farmers’ walks and deadlifts at 70% of their 1RM deadlift. Significant differences (p < 0.05) were apparent at knees passing with the farmers lift demonstrating greater trunk extension, thigh angle, knee flexion and ankle dorsiflexion. Significantly greater mean vertical and anterior forces were observed in the farmers lift than deadlift. The farmers walk demonstrated significantly greater peak forces and stride rates and significantly shorter stride lengths, ground contact times, and swing times than unloaded walk. Significantly greater dorsiflexion, knee flexion, thigh angle, and significantly lesser trunk angle at foot strike were also observed in the farmers walk. The farmers lift may be an effective lifting alternative to the deadlift, to generating more anterior-propulsive and vertical force with less stress to the lumbar spine due to the more vertical trunk position.
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In order to improve training performance, as well as avoid overloading during prevention and rehabilitation exercises in patients, the aim of this study was to understand the biomechanical differences in the knee, hip and the back between the exercises "Goodmornings" (GMs) and "Deadlifts" (DLs). The kinetics and kinematics of 13 subjects, performing GMs and DLs with an additional 25% (GMs), 25% and 50% (DLs) body weight (BW) on the barbell were analysed. Using the kinetic and kinematic data captured using a 3D motion analysis and force plates, an inverse approach with a quasi-static solution was used to calculate the sagittal moments and angles in the knee, hip and the trunk. The maximum moments and joint angles were statistically tested using ANOVA with a Bonferroni adjustment. The observed maximal flexion angle of the knee was 5.3 +/- 6.7[degree sign] for GMs and 107.8 +/- 22.4[degree sign] and 103.4 +/- 22.6[degree sign] for DLs with 25% and 50% BW respectively. Of the hip, the maximal flexion angle was 25% smaller during GMs compared to DLs. No difference in kinematics of the trunk between the two exercises was observed. For DLs, the resulting sagittal moment in the knee was an external flexion moment, whereas during GMs an external extension moment was present. Importantly, no larger sagittal knee joint moments were observed when using a heavier weight on the barbell during DLs, but higher sagittal moments were found at the hip and L4/L5. Compared to GMs, DLs produced a lower sagittal moment at the hip using 25% BW while generating the same sagittal moment at L4/L5. The two exercises exhibited different motion patterns for the lower extremities but not for the trunk. To strengthen the hip while including a large range of motion, DLs using 50% BW should be chosen. Due to their ability to avoid knee flexion or a knee flexion moment, GMs should be preferentially chosen over DLs as ACL rupture prevention exercises. Here, in order to shift the hamstring to quadriceps ratio towards the hamstrings, GMs should be favoured ahead of DLs using 50% BW before DLs using 25% BW.
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The primary purpose of this study was to examine the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors. A secondary aim was to analyze the relationships between training-induced changes in rapid torque and vertical jump performance. Fifty-four subjects (mean ± SD age = 23 ± 3 years) were randomly assigned to a control (n=20) or training group (n=34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and following the intervention. Torque - time curves were used to calculate rate of torque development (RTD) values at peak and 50 and 200ms from torque onset. Barbell deadlift training induced significant pre to post increases of 18.8-49.0% for all rapid torque variables (P<0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm ([7.4%] P<0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r=0.30-0.37, P<0.01-0.03). These findings showed that a 10 week barbell deadlift training program was effective at enhancing rapid torque capacities in both the knee extensors and flexors. Changes in rapid torque were associated with improvements in vertical jump height, suggesting a transfer of adaptations from deadlift training to an explosive, performance-based task. Professionals may use these findings when attempting to design effective, time efficient resistance training programs to improve explosive strength capacities in novices.
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The dorsal muscles of the lower torso and extremities have often been denoted the 'posterior chain.' These muscles are used to support the thoracic and lumbar spine as well as peripheral joints including the hip, knee, and ankle on the dorsal aspect of the body. This study investigated relative muscle activity of the hamstring group and selected surrounding musculature during the leg curl, good morning, glute-ham raise, and Romanian deadlift (RDL). Twelve healthy, weight trained men performed duplicate trials of single repetitions at 85% 1RM for each lift in random order, during which surface electromyography and joint angle data were obtained. Repeated measures analysis of variance (RMANOVA) across the four exercises was performed to compare activity from the erector spinae (ES), gluteus medius (GMed), semitendinosus (ST), biceps femoris (BF), and medial gastrocnemius (MGas). Significant differences (p<0.05) were noted in eccentric muscle activity between exercise for the MGas (p<0.027), ST (p<0.001), BF (p<0.001), and ES (p=0.032), and in concentric muscle activity for the ES (p<0.001), BF (p=0.010), ST (p=0.009), MGas (p<0.001), and the GMed (p=0.018). Bonferroni post hoc analysis revealed significant pairwise differences during eccentric actions for the BF, ST, and MGas. Post hoc analysis also revealed significant pairwise differences during concentric actions for the ES, BF, ST, MGas, and GMed. Each of these showed effect sizes that are large or greater. The main findings of this investigation are that the ST is substantially more active than the BF among all exercises, and hamstring activity was maximized in the RDL and glute-ham raise. Therefore, athletes and coaches who seek to maximize involvement of the hamstring musculature should consider focusing on the glute-ham raise and RDL.