Knee Observation Report
The Back squat is a predominantly lower-body exercise used extensively in strength and conditioning as a tool to quantify lower-body strength and as a training exercise, it’s also one of the three exercises evaluated in the sport of powerlifting.
Due to the competitive nature of powerlifting and the many federations that govern it, supportive equiptment is widely used to differing degrees between federations. Knee wraps are likely one of the most frequently utilised products of supportive equipment, used not only by powerlifters but also by recreational lifters and Olympic weightlifters (cite). Knee sleeves are commonly used in Olympic weightlifting as they offer knee support and warmth, without the bulk or increased restriction of Knee wraps. Knee wraps are a self-applied, multi-layered evolution of the knee sleeve providing increased elastic contribution. Evidence suggests that knee wraps have a …show more content…
positive effect on the weight an athlete can lift or the repetitions completed (Harman and Frykman, 1990; Totten, 1990; Gomes, Serpa, Soares, da Silva, Corrêa, Domingues de Oliveira, Neto, Martins, Junior, Marchetti, (2014); Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015)), and may not be solely beneficial for competition performance, but also as a strength training tool.
Typically knee wraps are constructed of cotton, polyester and rubber filaments that provide elasticity that aids the athlete during the lift and supports the knee; they are often applied by another person to ensure they are applied as tight as possible. This often causes substantial discomfort and can cause skin abrasion, the “scribe” effect, as well as a wedge like barrier behind the back of the knee, during the squat (Harman and Frykman, 1990).
Harman and Frykman (1990) originally identified the increased resultant force through the use of knee wraps through a simplistic study; more recently Lake, Carden and Shorter (2012). Reinforced these findings with similar results. Gomes, Serpa, Soares, da Silva, Corrêa, Domingues de Oliveira, Neto, Martins, Junior, Marchetti, (2014) Tested isometric strength with knee wraps, finding no significant differences between hard and soft knee wraps. Earlier this year Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015) investigated optimal knee wrap placement, concluding that the x-over pattern was the most effective for force production, the same method used by Harman and Frykman (1990) and Lake, J. P., Carden, P. J., & Shorter, K. A. (2012).
Lake, J. P., Carden, P. J., & Shorter, K. A. (2012) identified a horizontal shift in the barbell trajectory during the back squat when using knee wraps, yet Eitner, Lefavi and Riemann found no such effect in their study of the effect of knee wraps on back squat kinematics in 2011. The aims of this study are to clarify the effect that knee wraps have on back squat kinematics and kinetics, the results of this study could influence strength and condition considerations for athletes using knee wraps.
Literature Review
Purpose and Implications of use
Totten (1990) discusses the purpose of knee wraps, wrapping styles and the health implications of the use of knee wraps. Knee wraps are thought to be of assistance to heavy power and strength events and developing maximal power and strength (Totten, 1990), Harman and Frykman (1990) noted that many powerlifters relate knee wraps with an increase in weight lifted, the results presented suggest this association may be valid. Knee wraps affect knee function due to the inward pressure on the patella, resulting in the patella shifting position or being forced back causing the patella to grind against substructures below the patella (Totten 1990), resulting in chrondromalacia patellae, the wearing of the inner surface of the patella (Harman and Frykman 1990). The “scribe” effect may also occur as a result of the edge of the wrap digging into the skin, possibly causing micro-tears in the muscle and ligaments around the patella (Harman and Frykman, 1990 and Totten, 1990). Knee wraps gather behind the knee forming a “wedge-like” barrier that pushes the bones forming the knee joint apart. Knee wraps do not “support” the knee, and likely increase the risk of injury (Totten, 1990). Knee wraps can be bulky and restrictive, as well as reduce speed in Olympic weightlifting (Harman and Frykman, 1990 and Totten, 1990),The increased knee temperature achieved with knee wraps helps prevent friction, although this can be achieved with knee sleeves without the disadvantages (Totten, 1990). Harman and Frykman, (1990) and Totten, (1990) both agree that most of these negative effects can be mitigated through reduced frequency of use, both articles are informed by the experience of professionals working with the U.S. Weightlifting Federation, as well as the testimonials of professional athletes who frequently use knee wraps and as a result are observational in nature rather than research based. Both papers form the foundation for future research, and conclude that knee wraps offer no reasonable support to the ligaments of the knee and are purely ergogenic aids.
Performance Characteristics
Harman and Frykman (1990) lowered a participant with and without knee wraps onto a weighing scale, the participant was lowered until squat depth was reached; for this method to be accurate the participant has to be completely relaxed; the effect of the knee wrap binding behind the knee could be responsible for a proportion of the effects observed. Harman and Frykman (1990) also used varying numbers of rotations of the knee wraps dependant on the girth of the participant’s legs, possibly providing smaller participants with increased support. Regardless Harman and frykman (1990) showed that knee wraps did provide a positive force in a squat position, which was taken further in 2012 by Lake, Carden and Shorter who assessed the mechanical output and performance characteristics that knee wraps impose during the back squat controlling the number of rotation of knee wraps. Lake, Carden and Shorter (2012) found an Increase in peak power, vertical lifting impulse and barbell displacement during the descent phase of the squat as well as a decrease in the descent duration. Although these are mostly positive results, Lake, Carden and Shorter (2012) concluded that knee wraps could impede the development of balanced lower-body musculature, modify body position during the back squat and comprise knee joint integrity. Gomes et al. (2014) performed 3 maximal isometric contractions in a squat position with soft and hard knee wraps as well as without, finding that knee wrapped conditions performed significantly better than without but without a significant difference between the two, although more rotations were used with the softer knee wraps. Gomes et al. (2014) concluded that knee wraps would have an influence on strength performance. Knee wraps have not directly been shown to increase 1RM back squat, although research and observation strongly correlate the two. Knee wraps could be a useful tool for strength and conditioning coaches since they allow a greater stimulus of an increased weight, and help achieve faster speeds at a given weight. Knee wraps have been shown to aid knee extension; increased capacity for knee extension without increased hip extension ability is likely to result in a change in technique.
Application Technique
Marchetti, et al.(2015) investigated the contribution of two different knee wrapping styles to an isometric contraction in a similar protocol to Gomes et al. (2014), results showed that the X style, used by Harman and frykmen, Lake, Either?, was superior to the spiral technique by 3%, which was not significantly different.
It doesn’t really matter
Biomechanical alterations
Eitner, Lefavi, and Riemann (2011) investigated the effects of knee wraps on the kinetics and kinematics on the back squat with trained powerlifters finding no significant change in biomechanics whereas Lake et al. (2012) found increased horizontal displacement in the descent phase as well as significant changes in mechanical outputs resistance trained athletes who do not frequently use knee wraps. This disparity may be a result of the different sample of subjects used in each study, it’s possible that those who frequently use knee wraps adapt to the assistance and adjust accordingly, as well as a possible change in the distribution of muscle mass and long term technique alterations e.g. wider stance with reduced Knee flexion.
Ethical Considerations
The research suggests that the use of knee wraps may be considered unethical and cause long term damage to the knee when used frequently or excessively tight (Harman and Frykman, 1990 and Totten, 1990), however some athletes may risk long term injury for short term benefits (Harman and Frykman; Lake et al; Gomes et al and Marchetti, et al.2015). The lenient rules of some powerlifting federations may not wish to change due to a decrease in standards; although this may benefit powerlifting by removing equipment that may alienate would be fans and help the sport become an Olympic sport.
Methods
A counterbalanced design was used to measure the effects of knee wraps on back squat technique, hip, knee and ankle angles were measured in order to quantify the deviations from each participant’s normal squat technique and identify trends. Relative lowering and lifting phase durations’ were also measured.
Resistance trained men with at least one year’s experience of squatting frequently took part in the study. Participants had either no or little experience with knee wraps, to this end each participant underwent two familiarisation sessions. All participants were capable of squatting to full depth, where the “top surface of the legs at the hip joint is lower than the top of the knees” which is the criteria used by the international powerlifting federation (IPF, 2015), the largest powerlifting federation. (cite??)
Testing required both wrapped and unwrapped squats to be observed, half of the participants began with wrapped squats and the remaining began with unwrapped. Relative lowering and lifting phase durations’ were recorded during the back squat exercise, whilst the sagittal and frontal plane were recorded in order to record joint angles at depth during both the descent and ascent of the squat, and ensure external rotation remained consistent. The Exercise was performed at 80% of their 1-repetition maximum (1RM). Figure 1. shows the recorded sagittal plane of the exercise and the joint angles measured.
Subjects
8 resistance trained men volunteered to take part, with a mean (SD) back squat experience of 3.75 (1.67)years, 1 participant had used knee wraps before and 7 had no experience of using knee wraps. Physical and performance characteristic’s include a mean (SD) age 23.75 (3.06)years, bodyweight of 83.34 (9.15)kg, height of 180.05 (7.08)cm and a 1RM of 137 (31)kg, with an external rotation of 12.63 (3.89)degrees from a neutral foot alignment.
Since none of the participants used knee wraps frequently, two familiarisation sessions were completed by all participants to mitigate the influence of learning or variation during the testing.
The first familiarisation session was completed after the 1RM testing on the Monday and the second on the Wednesday. Familiarisation sessions consisted of 2 sets of 6 wrapped squats at 60% 1RM and 2 sets of 2 squats performed at 80% 1RM. The main testing was then completed on the Friday; participants were advised to avoid any vigorous exercise before the 1RM testing and main testing. Both the 1RM and main testing were completed at the same time of day for all participants.
Procedures
The main testing was completed on the Friday, six repetitions of back squats were performed at 80% of each subjects 1RM, three with and three without knee wraps, very similar to Lake, Carden, and Shorter, (2012), using the same warmup protocol for 1RM testing and the main testing as Wallace, Winchester and McGuigan, (2006) and Lake, Carden, and Shorter, (2012), detailed in the Figure 2.
below.
The load was selected to represent a typical training load as well as to allow comparisons to Lake, Carden, and Shorter, (2012) who used the same load. Half of the participants performed wrapped squats first, half performed unwrapped first so as to remove any fatigue or completion order effects. A rest period of three minutes was imposed, Matusza, Fry, Weiss, Ireland, & Mcknight, (2003) found no significant difference in performance using 1, 3 and 5 minute rest periods for 1RM testing, 3 minutes had the highest success rate and was chosen as a suitable medium. One set of 2 metre IPF approved Red Devil Knee Wraps (Pullum Sports, Bedfordshire, United Kingdom) were used, similar to those used by (Lake, Carden, and Shorter, 2012; Harman and Frykman and Gomes et al) (with a length and width of?? Easured with calipers). The same figure of eight method of wrapping used by (Lake, Carden, and Shorter, 2012; Harman and Frykman; and Gomes et al) was used and was recently found to be the most effective in an isometric test by Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015). The same experimenter applied the knee wraps as tightly as possible before each repetition in the main testing, 6 rotations were used for every participant to standardize resistance, with an achievable amount of rotations for all of the participants.
Hip, knee and ankle angles were recorded and analysed with 2d video analysis similar to that used by Hooper, Szivak, Comstock, Dunn-Lewis, Apicella, Kelly, Creighton, Flanagan, Looney, Volek, Maresh and Kraemer, (2014) in their enquiry into back squat technique. One camera (what fucking camera?) was placed laterally 4m away from the participant in the sagittal plane, in line with the lateral malleolus, at the height of the top of each participant’s. This position is optimal in effectively determining joint angles with 2-dimensional analysis as the middle two markers for the joint angles are positioned in the middle of the frame.
(Dartfish 7 ClassroomPlus 7.0, build 11105) was used to analyse the joint angles when the participant reached depth during the descent and again as they ascended, this was as to accurately depicted the horizontal shift of the barbell as the ascent begins (cite lake). The anatomical markers used were, the end of the barbell, lateral to the anterior superior iliac spine, lateral to the superior aspect of the patella (base), lateral malleolus and parallel to the floor at the height of the lateral malleolus. No footwear was permitted, and all participants used a high bar loading position, Figure 3. depicts this above, the anatomical markers used are very similar to (back squat fatigue study)
Another camera was placed in front of the participant to ensure foot position and external rotation remained constant throughout the movement, lines and markers were used to prompt the participant to use the same stance width, external rotation and camera alignment. External rotation and stance width were measured during the 1RM testing day, center to center calcaneus and hallux separation were recorded and marked for the main testing day, as well as foot length was recorded to be marked for the testing day and to calculate average external rotation.
The testing was completed using an Eleiko International training bar and olympic weightlifting training coloured discs (Eleiko Sport AB, Korsvägen 31, SE-302 56 Halmstad, sweden) and Power-Lift Multi rack and olympic platform (Conner Athletic Products, Inc. P.O. Box 348, 900 East Hwy 30, Jefferson, Iowa, 50129, U.S.A),
all statistical analysis and related t-tests were performed with excel.
The descent phase was measured from the highest initial position at the top of the squat and the lowest barbell position, with the ascent phase being the return form the lowest barbell position to the highest, the differences between the times at these frames are used to determine ascent, descent, and total duration for back squat. The last frames during the descent when the participant is at or below depth is when the joint angles are measured, this accounts for any shift in the position of the barbell in the bottom of the squat. All of the wrapped and unwrapped squats were used to calculate the significance of the results with a repeated measure? T-test, with the average being used to calculate the mean and standard deviation for each joint angle and time.
Results
The results show that knee wraps significantly reduced the RoM (Range of Motion) achieved by the ankle and knee at depth and increased Hip RoM at depth for both the descent and ascent phases. No significant change was observed in the total duration, or time taken to ascend, but the time taken to descend was shown to be significantly increased.
Table 1. Joint angles and duration across the decent and ascent phases
Joint Phase Unwrapped Wrapped %difference P
Hip D 57.4±10.1 55.1±9.6 4.1±4.3 *<0.000
Ankle D 55.4±2.2 56.5±2.7 -2.0±21.0 *0.001 A 53.6±4.0 54.1±4.2 -1.0±6.3 *0.048
Duration D 1.663±0.117 1.767±0.215 6.1±59.2 *0.008 A 1.594±0.095 1.576±0.122 -1.1±24.4 0.248
Total Duration 3.256±0.135 3.343±0.261 2.6±63.5 0.069
*denotes statistical significance with a given alpha level of 0.05
D=descent phase, A=ascent phase
A negative %difference indicates a decrease range of motion or decreased time.
Discussion
Joint Angles
The reduced RoM at the Knee observed was expected, and most likely due to “wedge-like effect” and elastic resistance of the knee wraps
An increased RoM at the Hip was expected to account for Knee restriction and was observed in the results.
There are two ways an athlete can compensate for a reduce range of motion at the knees in order to maintain balance, either by increasing dorsiflexion, which would Increase the required flexion at the knees in order to reach depth, or Increasing flexion at the Hips. Increasing Hip flexion allows the load to move forward, reducing dorsiflexion and allowing depth to be reached with reduced Knee flexion. The reduced RoM at the Ankle observed was most likely a result of this mechanism.
The overall differences in technique were larger during the descent phase, although both were significant; the knee wraps had a larger significance during the descent. Why?
Phase Duration
The descent phase duration was expected to be reduced, since the knee wraps are assisting in the deceleration of the barbell. However there was a significant Increase in the descent duration, this is most likely due to the relative novelty of the knee wraps to the participants, leading to a cautious descent rather than a confident reliance on the supportive equipment.
Likewise a reduced ascent time was predicted and the result was found to be reduced, but was not significant. The stored elastic energy in the wrap should assist the participant in driving up from the bottom of the squat. The participants were not instructed to complete the repetitions as was as possible, and this could be the reason for both the increased descent time and insignificant increase In ascent time. Without an instructed time constraint or target than the knee wraps may support the participant in taking their time performing their perception of the most biomechanically appropriate back squat.
The total duration of the back squat was expected to be decreased, but was found to have an insignificant Increase, again this may be both a result of the participants approach from the instruction given, and the novelty of knee wraps to the participant. The participants had undergone two session of familiarisation, and as a result should be fairly comfortable with the elastic response, I should have said squat fast.
Related literature
Eitner, Lefavi, and Riemann (2011) used a load of around 70% of 1RM (12RM), with trained powerlifters and found no significant changes in technique
This could be due to an altered technique; powerlifters commonly adopt a wider stance
Also could be a result of frequent training with knee wraps leading to a different distribution of muscle mass that might not elicit a noticeable difference in technique at the load used, which was a comparative 10% reduction in the relative percentage of the 1RM
Due to the competitive nature of powerlifting and the many federations that govern it, supportive equiptment is widely used to differing degrees between federations. Knee wraps are likely one of the most frequently utilised products of supportive equipment, used not only by powerlifters but also by recreational lifters and Olympic weightlifters (cite). Knee sleeves are commonly used in Olympic weightlifting as they offer knee support and warmth, without the bulk or increased restriction of Knee wraps. Knee wraps are a self-applied, multi-layered evolution of the knee sleeve providing increased elastic contribution. Evidence suggests that knee wraps have a …show more content…
positive effect on the weight an athlete can lift or the repetitions completed (Harman and Frykman, 1990; Totten, 1990; Gomes, Serpa, Soares, da Silva, Corrêa, Domingues de Oliveira, Neto, Martins, Junior, Marchetti, (2014); Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015)), and may not be solely beneficial for competition performance, but also as a strength training tool.
Typically knee wraps are constructed of cotton, polyester and rubber filaments that provide elasticity that aids the athlete during the lift and supports the knee; they are often applied by another person to ensure they are applied as tight as possible. This often causes substantial discomfort and can cause skin abrasion, the “scribe” effect, as well as a wedge like barrier behind the back of the knee, during the squat (Harman and Frykman, 1990).
Harman and Frykman (1990) originally identified the increased resultant force through the use of knee wraps through a simplistic study; more recently Lake, Carden and Shorter (2012). Reinforced these findings with similar results. Gomes, Serpa, Soares, da Silva, Corrêa, Domingues de Oliveira, Neto, Martins, Junior, Marchetti, (2014) Tested isometric strength with knee wraps, finding no significant differences between hard and soft knee wraps. Earlier this year Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015) investigated optimal knee wrap placement, concluding that the x-over pattern was the most effective for force production, the same method used by Harman and Frykman (1990) and Lake, J. P., Carden, P. J., & Shorter, K. A. (2012).
Lake, J. P., Carden, P. J., & Shorter, K. A. (2012) identified a horizontal shift in the barbell trajectory during the back squat when using knee wraps, yet Eitner, Lefavi and Riemann found no such effect in their study of the effect of knee wraps on back squat kinematics in 2011. The aims of this study are to clarify the effect that knee wraps have on back squat kinematics and kinetics, the results of this study could influence strength and condition considerations for athletes using knee wraps.
Literature Review
Purpose and Implications of use
Totten (1990) discusses the purpose of knee wraps, wrapping styles and the health implications of the use of knee wraps. Knee wraps are thought to be of assistance to heavy power and strength events and developing maximal power and strength (Totten, 1990), Harman and Frykman (1990) noted that many powerlifters relate knee wraps with an increase in weight lifted, the results presented suggest this association may be valid. Knee wraps affect knee function due to the inward pressure on the patella, resulting in the patella shifting position or being forced back causing the patella to grind against substructures below the patella (Totten 1990), resulting in chrondromalacia patellae, the wearing of the inner surface of the patella (Harman and Frykman 1990). The “scribe” effect may also occur as a result of the edge of the wrap digging into the skin, possibly causing micro-tears in the muscle and ligaments around the patella (Harman and Frykman, 1990 and Totten, 1990). Knee wraps gather behind the knee forming a “wedge-like” barrier that pushes the bones forming the knee joint apart. Knee wraps do not “support” the knee, and likely increase the risk of injury (Totten, 1990). Knee wraps can be bulky and restrictive, as well as reduce speed in Olympic weightlifting (Harman and Frykman, 1990 and Totten, 1990),The increased knee temperature achieved with knee wraps helps prevent friction, although this can be achieved with knee sleeves without the disadvantages (Totten, 1990). Harman and Frykman, (1990) and Totten, (1990) both agree that most of these negative effects can be mitigated through reduced frequency of use, both articles are informed by the experience of professionals working with the U.S. Weightlifting Federation, as well as the testimonials of professional athletes who frequently use knee wraps and as a result are observational in nature rather than research based. Both papers form the foundation for future research, and conclude that knee wraps offer no reasonable support to the ligaments of the knee and are purely ergogenic aids.
Performance Characteristics
Harman and Frykman (1990) lowered a participant with and without knee wraps onto a weighing scale, the participant was lowered until squat depth was reached; for this method to be accurate the participant has to be completely relaxed; the effect of the knee wrap binding behind the knee could be responsible for a proportion of the effects observed. Harman and Frykman (1990) also used varying numbers of rotations of the knee wraps dependant on the girth of the participant’s legs, possibly providing smaller participants with increased support. Regardless Harman and frykman (1990) showed that knee wraps did provide a positive force in a squat position, which was taken further in 2012 by Lake, Carden and Shorter who assessed the mechanical output and performance characteristics that knee wraps impose during the back squat controlling the number of rotation of knee wraps. Lake, Carden and Shorter (2012) found an Increase in peak power, vertical lifting impulse and barbell displacement during the descent phase of the squat as well as a decrease in the descent duration. Although these are mostly positive results, Lake, Carden and Shorter (2012) concluded that knee wraps could impede the development of balanced lower-body musculature, modify body position during the back squat and comprise knee joint integrity. Gomes et al. (2014) performed 3 maximal isometric contractions in a squat position with soft and hard knee wraps as well as without, finding that knee wrapped conditions performed significantly better than without but without a significant difference between the two, although more rotations were used with the softer knee wraps. Gomes et al. (2014) concluded that knee wraps would have an influence on strength performance. Knee wraps have not directly been shown to increase 1RM back squat, although research and observation strongly correlate the two. Knee wraps could be a useful tool for strength and conditioning coaches since they allow a greater stimulus of an increased weight, and help achieve faster speeds at a given weight. Knee wraps have been shown to aid knee extension; increased capacity for knee extension without increased hip extension ability is likely to result in a change in technique.
Application Technique
Marchetti, et al.(2015) investigated the contribution of two different knee wrapping styles to an isometric contraction in a similar protocol to Gomes et al. (2014), results showed that the X style, used by Harman and frykmen, Lake, Either?, was superior to the spiral technique by 3%, which was not significantly different.
It doesn’t really matter
Biomechanical alterations
Eitner, Lefavi, and Riemann (2011) investigated the effects of knee wraps on the kinetics and kinematics on the back squat with trained powerlifters finding no significant change in biomechanics whereas Lake et al. (2012) found increased horizontal displacement in the descent phase as well as significant changes in mechanical outputs resistance trained athletes who do not frequently use knee wraps. This disparity may be a result of the different sample of subjects used in each study, it’s possible that those who frequently use knee wraps adapt to the assistance and adjust accordingly, as well as a possible change in the distribution of muscle mass and long term technique alterations e.g. wider stance with reduced Knee flexion.
Ethical Considerations
The research suggests that the use of knee wraps may be considered unethical and cause long term damage to the knee when used frequently or excessively tight (Harman and Frykman, 1990 and Totten, 1990), however some athletes may risk long term injury for short term benefits (Harman and Frykman; Lake et al; Gomes et al and Marchetti, et al.2015). The lenient rules of some powerlifting federations may not wish to change due to a decrease in standards; although this may benefit powerlifting by removing equipment that may alienate would be fans and help the sport become an Olympic sport.
Methods
A counterbalanced design was used to measure the effects of knee wraps on back squat technique, hip, knee and ankle angles were measured in order to quantify the deviations from each participant’s normal squat technique and identify trends. Relative lowering and lifting phase durations’ were also measured.
Resistance trained men with at least one year’s experience of squatting frequently took part in the study. Participants had either no or little experience with knee wraps, to this end each participant underwent two familiarisation sessions. All participants were capable of squatting to full depth, where the “top surface of the legs at the hip joint is lower than the top of the knees” which is the criteria used by the international powerlifting federation (IPF, 2015), the largest powerlifting federation. (cite??)
Testing required both wrapped and unwrapped squats to be observed, half of the participants began with wrapped squats and the remaining began with unwrapped. Relative lowering and lifting phase durations’ were recorded during the back squat exercise, whilst the sagittal and frontal plane were recorded in order to record joint angles at depth during both the descent and ascent of the squat, and ensure external rotation remained consistent. The Exercise was performed at 80% of their 1-repetition maximum (1RM). Figure 1. shows the recorded sagittal plane of the exercise and the joint angles measured.
Subjects
8 resistance trained men volunteered to take part, with a mean (SD) back squat experience of 3.75 (1.67)years, 1 participant had used knee wraps before and 7 had no experience of using knee wraps. Physical and performance characteristic’s include a mean (SD) age 23.75 (3.06)years, bodyweight of 83.34 (9.15)kg, height of 180.05 (7.08)cm and a 1RM of 137 (31)kg, with an external rotation of 12.63 (3.89)degrees from a neutral foot alignment.
Since none of the participants used knee wraps frequently, two familiarisation sessions were completed by all participants to mitigate the influence of learning or variation during the testing.
The first familiarisation session was completed after the 1RM testing on the Monday and the second on the Wednesday. Familiarisation sessions consisted of 2 sets of 6 wrapped squats at 60% 1RM and 2 sets of 2 squats performed at 80% 1RM. The main testing was then completed on the Friday; participants were advised to avoid any vigorous exercise before the 1RM testing and main testing. Both the 1RM and main testing were completed at the same time of day for all participants.
Procedures
The main testing was completed on the Friday, six repetitions of back squats were performed at 80% of each subjects 1RM, three with and three without knee wraps, very similar to Lake, Carden, and Shorter, (2012), using the same warmup protocol for 1RM testing and the main testing as Wallace, Winchester and McGuigan, (2006) and Lake, Carden, and Shorter, (2012), detailed in the Figure 2.
below.
The load was selected to represent a typical training load as well as to allow comparisons to Lake, Carden, and Shorter, (2012) who used the same load. Half of the participants performed wrapped squats first, half performed unwrapped first so as to remove any fatigue or completion order effects. A rest period of three minutes was imposed, Matusza, Fry, Weiss, Ireland, & Mcknight, (2003) found no significant difference in performance using 1, 3 and 5 minute rest periods for 1RM testing, 3 minutes had the highest success rate and was chosen as a suitable medium. One set of 2 metre IPF approved Red Devil Knee Wraps (Pullum Sports, Bedfordshire, United Kingdom) were used, similar to those used by (Lake, Carden, and Shorter, 2012; Harman and Frykman and Gomes et al) (with a length and width of?? Easured with calipers). The same figure of eight method of wrapping used by (Lake, Carden, and Shorter, 2012; Harman and Frykman; and Gomes et al) was used and was recently found to be the most effective in an isometric test by Marchetti, Matos, Soares, da Silva, Serpa, Corrêa, Martins, Junior, and Gomes, (2015). The same experimenter applied the knee wraps as tightly as possible before each repetition in the main testing, 6 rotations were used for every participant to standardize resistance, with an achievable amount of rotations for all of the participants.
Hip, knee and ankle angles were recorded and analysed with 2d video analysis similar to that used by Hooper, Szivak, Comstock, Dunn-Lewis, Apicella, Kelly, Creighton, Flanagan, Looney, Volek, Maresh and Kraemer, (2014) in their enquiry into back squat technique. One camera (what fucking camera?) was placed laterally 4m away from the participant in the sagittal plane, in line with the lateral malleolus, at the height of the top of each participant’s. This position is optimal in effectively determining joint angles with 2-dimensional analysis as the middle two markers for the joint angles are positioned in the middle of the frame.
(Dartfish 7 ClassroomPlus 7.0, build 11105) was used to analyse the joint angles when the participant reached depth during the descent and again as they ascended, this was as to accurately depicted the horizontal shift of the barbell as the ascent begins (cite lake). The anatomical markers used were, the end of the barbell, lateral to the anterior superior iliac spine, lateral to the superior aspect of the patella (base), lateral malleolus and parallel to the floor at the height of the lateral malleolus. No footwear was permitted, and all participants used a high bar loading position, Figure 3. depicts this above, the anatomical markers used are very similar to (back squat fatigue study)
Another camera was placed in front of the participant to ensure foot position and external rotation remained constant throughout the movement, lines and markers were used to prompt the participant to use the same stance width, external rotation and camera alignment. External rotation and stance width were measured during the 1RM testing day, center to center calcaneus and hallux separation were recorded and marked for the main testing day, as well as foot length was recorded to be marked for the testing day and to calculate average external rotation.
The testing was completed using an Eleiko International training bar and olympic weightlifting training coloured discs (Eleiko Sport AB, Korsvägen 31, SE-302 56 Halmstad, sweden) and Power-Lift Multi rack and olympic platform (Conner Athletic Products, Inc. P.O. Box 348, 900 East Hwy 30, Jefferson, Iowa, 50129, U.S.A),
all statistical analysis and related t-tests were performed with excel.
The descent phase was measured from the highest initial position at the top of the squat and the lowest barbell position, with the ascent phase being the return form the lowest barbell position to the highest, the differences between the times at these frames are used to determine ascent, descent, and total duration for back squat. The last frames during the descent when the participant is at or below depth is when the joint angles are measured, this accounts for any shift in the position of the barbell in the bottom of the squat. All of the wrapped and unwrapped squats were used to calculate the significance of the results with a repeated measure? T-test, with the average being used to calculate the mean and standard deviation for each joint angle and time.
Results
The results show that knee wraps significantly reduced the RoM (Range of Motion) achieved by the ankle and knee at depth and increased Hip RoM at depth for both the descent and ascent phases. No significant change was observed in the total duration, or time taken to ascend, but the time taken to descend was shown to be significantly increased.
Table 1. Joint angles and duration across the decent and ascent phases
Joint Phase Unwrapped Wrapped %difference P
Hip D 57.4±10.1 55.1±9.6 4.1±4.3 *<0.000
Ankle D 55.4±2.2 56.5±2.7 -2.0±21.0 *0.001 A 53.6±4.0 54.1±4.2 -1.0±6.3 *0.048
Duration D 1.663±0.117 1.767±0.215 6.1±59.2 *0.008 A 1.594±0.095 1.576±0.122 -1.1±24.4 0.248
Total Duration 3.256±0.135 3.343±0.261 2.6±63.5 0.069
*denotes statistical significance with a given alpha level of 0.05
D=descent phase, A=ascent phase
A negative %difference indicates a decrease range of motion or decreased time.
Discussion
Joint Angles
The reduced RoM at the Knee observed was expected, and most likely due to “wedge-like effect” and elastic resistance of the knee wraps
An increased RoM at the Hip was expected to account for Knee restriction and was observed in the results.
There are two ways an athlete can compensate for a reduce range of motion at the knees in order to maintain balance, either by increasing dorsiflexion, which would Increase the required flexion at the knees in order to reach depth, or Increasing flexion at the Hips. Increasing Hip flexion allows the load to move forward, reducing dorsiflexion and allowing depth to be reached with reduced Knee flexion. The reduced RoM at the Ankle observed was most likely a result of this mechanism.
The overall differences in technique were larger during the descent phase, although both were significant; the knee wraps had a larger significance during the descent. Why?
Phase Duration
The descent phase duration was expected to be reduced, since the knee wraps are assisting in the deceleration of the barbell. However there was a significant Increase in the descent duration, this is most likely due to the relative novelty of the knee wraps to the participants, leading to a cautious descent rather than a confident reliance on the supportive equipment.
Likewise a reduced ascent time was predicted and the result was found to be reduced, but was not significant. The stored elastic energy in the wrap should assist the participant in driving up from the bottom of the squat. The participants were not instructed to complete the repetitions as was as possible, and this could be the reason for both the increased descent time and insignificant increase In ascent time. Without an instructed time constraint or target than the knee wraps may support the participant in taking their time performing their perception of the most biomechanically appropriate back squat.
The total duration of the back squat was expected to be decreased, but was found to have an insignificant Increase, again this may be both a result of the participants approach from the instruction given, and the novelty of knee wraps to the participant. The participants had undergone two session of familiarisation, and as a result should be fairly comfortable with the elastic response, I should have said squat fast.
Related literature
Eitner, Lefavi, and Riemann (2011) used a load of around 70% of 1RM (12RM), with trained powerlifters and found no significant changes in technique
This could be due to an altered technique; powerlifters commonly adopt a wider stance
Also could be a result of frequent training with knee wraps leading to a different distribution of muscle mass that might not elicit a noticeable difference in technique at the load used, which was a comparative 10% reduction in the relative percentage of the 1RM