
==== Front
Int J Sports Phys Ther
Int J Sports Phys Ther
2159
International Journal of Sports Physical Therapy
2159-2896
NASMI Website: International Journal of Sports Physical Therapy

38576837
94610
10.26603/001c.94610
Original Research
Quadriceps and Hamstrings Activation Peaks Earlier as Athletes Repeatedly Hop, but There are Differences Depending on ACL Reconstruction Technique.
Einarsson Einar 1
Barbosa Olivia 2
Gislason Magnus Kjartan 3
Briem Kristin 4
Kotsifaki Argyro 2
Whiteley Rodney 2
1 School of Engineering University of Reykjavik
2 Rehabilitation Qatar Orthopaedic and Sports Medicine Hospital https://ror.org/00x6vsv29
3 School of Engineering University of Reykjavik
4 Department of Physical Therapy University of Iceland https://ror.org/01db6h964
Corresponding author: Einar Einarsson University of Reykjavik, School of Engineering, Menntavegur 1, 102 Reykjavik Iceland Tel: +354 5996200 Fax: Email: einarei@ru.is
1 4 2024
2024
19 4 418428
23 3 2023
28 1 2024
© The Author(s)
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (4.0) which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.

Background

After Anterior Cruciate Ligament Reconstruction (ACLR) athletes face the challenge of regaining their previous competitive level while avoiding re-injury and early knee joint cartilage degeneration. Quadriceps and hamstrings strength reductions and neuromuscular alterations potentially related to risk of re-injury are present after ACLR and relate to deficits in muscle activation.

Design

Cross-sectional laboratory study

Purpose

To examine quadriceps and hamstrings muscle activation during repeated hops in healthy pivoting-sport athletes and those who had undergone ACLR (bone-tendon-bone and semitendinosus graft) who had met functional criteria allowing return to training.

Methods

Surface electromyography (SEMG) was recorded from vastus medialis and lateralis and medial and lateral hamstrings bilaterally during 30 seconds’ repeated hopping in male athletes on average eight months after ACLR surgery (5-12 months). All patients underwent hamstring (HS) (n=24) or bone-tendon-bone (BTB) reconstruction (n=20) and were compared to healthy controls (n=31). The SEMG signals were normalized to those obtained during maximal voluntary isometric contraction.

Results

A significant time shift in peak muscle activation (earlier) was seen for: vastus medialis and vastus lateralis activation in the control group, in the BTB group’s healthy (but not injured) leg and both legs of the HS group. A significant time shift in peak muscle activation was seen for lateral hamstrings (earlier) in all but the BTB group’s injured leg and the medial hamstrings in the control group only. Lower peak activation levels of the vastus lateralis (p<0.001) and vastus medialis (p<0.001) were observed in the injured compared to healthy legs and lower peak lateral hamstrings activity (p<0.009) in the injured leg compared to control leg. Decline in medial hamstring peak activation (p<0.022) was observed between 1st and 3rd phase of the hop cycle in all groups.

Conclusion

Repeated hop testing revealed quadriceps and hamstring activation differences within ACLR athletes, and compared to healthy controls, that would be missed with single hop tests.

Level of evidence

3

electromyography
anterior cruciate ligament
rehabilitation
injury
==== Body
pmcINTRODUCTION

Athletes having surgery after anterior cruciate ligament (ACL) injury expect to return to sport with more than 90% of previous injury level capacity1 yet only 55-60 % will return to their previous competitive level.2 Additionally, those undergoing ACL reconstruction (ACLR) have a higher risk of reinjury3 and osteoarthritis4 and show worse subsequent performance and career duration.5 Reasons for reduced participation and impaired performance are complex6 and while results from return to sport (RTS) testing after ACLR can be useful to estimate the athlete’s readiness to participate in sports,7 clinical testing methods often used as a measure of lower limb function do not always identify specific local impairments8 likely due to compensatory strategies9 which suggests alternative RTS evaluations might be required.7

Surface electromyographical (SEMG) analysis can help identify alterations in neuromuscular control, however this is rarely used in RTS assessment.10 While ACLR patients demonstrate continued alterations in neuromuscular control11 it is not clear which SEMG measuring method would inform the RTS decision regarding readiness to return to sport.10 SEMG can provide information about: the absolute magnitude of muscle activation, the relative timing of muscle activation during a single action, and changes in magnitude and timing during repeated actions.

Regarding the absolute magnitude, ACLR patients likely have a reduction in quadriceps activation. Quadriceps strength is often reported to be lower during MVIC strength testing (compared to their uninjured leg12 and controls13) even years after returning to sport and quadriceps and hamstring strength reductions are associated with reduced performance and risk of reinjury in ACL reconstructed individuals compared to controls at RTS14,15 and up to four years after surgery.16 Changes in muscle activation are thought to play a role in these deficits13 as strength loss does not fully explain the biomechanical differences observed between athletes that did not sustain re-injury after ACLR (greater knee flexion, increased contact time).17 Persistent neuromuscular alterations which could be related to risk of re-injury are present after ACLR18 and can be identified during the rehabilitation process.19

With regard to the timing of muscle activation, co-contraction of the quadriceps and hamstrings at the time of landing is thought to be a protective mechanism for knee joint stability. Neuromuscular alterations, including earlier thigh muscle onset and increased duration of activation pre-landing, are seen in ACLR athletes during a variety of different drop jump landing tasks20 and after inducing fatigue.21 Information regarding time to peak activity are sparse but delayed time to peak activation in quadriceps and hamstrings compared to the healthy leg has been reported in a jump cut task in ACLR males,22 which may negatively affect attenuation of knee loading during drop jump landing.23 Athletes who have undergone ACLR have also shown lower quadriceps activation but increased hamstring pre-activity often thought of as protective mechanism to control translation before landing in a repeated jump squat task.24

Commonly, ACLR is conducted using either an autologous hamstring (HS) or bone-patellar-tendon-bone graft (BTB). The surgical technique is seen to have an effect on quadriceps and hamstrings muscle strength15 but it is not known if there are persisting differences in relative activation of these muscles during repeated functional tasks.

A single leg countermovement jump appears to be a valid return to sport test that will identify deficits in knee function in ACLR athletes.25 Information from a single event such as a drop jump or single cutting movement may not represent the full demands of sporting activity where athletes perform repeated movements, often to the point of muscle failure. More information may be found in a repeated hopping task which might reveal differences in muscle activation patterns as athletes’ fatigue. A 30-second maximum effort hopping task has been shown to induce decline in physical performance throughout the task.26

Therefore, the purpose of this study was to examine quadriceps and hamstrings muscle activation during repeated hops in healthy pivoting-sport athletes and those who had undergone ACLR (bone-tendon-bone and semitendinosus graft) who had met functional criteria allowing return to training. In particular, the intent was to document the peak muscle activation of the quadriceps and hamstrings during the initial (first 10 seconds) and final (last 10 seconds) of a fatiguing hop task as well as the typical pattern of muscle activation during the individual hops performed during these periods. By examining both legs of the athletes who had undergone ACLR (both hamstring and bone-patellar tendon-bone grafts) and comparing to uninjured healthy controls the authors attempted to better understand any effect on both the timing and magnitude of activity in relation to surgical technique.

The hypothesis was that there would be a change in time to peak and absolute magnitude of activation as participants tire, and that the surgical technique (graft choice) would be associated with specific differences in the activation patterns seen.

METHODS

Study participants

Male participants (“patients”) who had undergone an isolated ACLR either with BTB or HS graft and a comparison cohort of active healthy adults (“control”) were recruited for the study. All patients participated in pivoting sports and were all at level 9 or 10 on the Tegner scale. The athletes had completed all clinical criteria (<10% deficit on isokinetic and functional field testing, pain-free, no swelling on swipe test, and full ROM)27 and had demonstrated competence in repeated single leg hops during rehabilitation. All controls were injury-free in the last three months prior to the assessment, had never had a major lower limb injury such as a 3rd degree ligament sprain or ACLR, fracture of bone in lower leg, or 3rd degree muscle strain which could affect neuromuscular profiles. Informed consent was obtained for each volunteer participant and the experiment was conducted with the approval of the local ethics committee.

Recording of muscle activation and normalization

Muscle activation was examined28 by means of wireless surface electromyography (SEMG) signals (hereafter termed ‘muscle activation’) of the quadriceps muscles (vastus medialis and vastus lateralis) and hamstrings muscles (lateral hamstring and medial hamstring) of both legs during a minimum of 30 seconds repeated single leg countermovement hopping.

SEMG data collection was performed after a 10-minute warm up on a stationary bike, by having skin shaved and cleaned with alcohol swabs (70%), and electrodes were placed following SENIAM guidelines.28 Muscle activation SEMG from vastus medialis and vastus lateralis and lateral hamstrings and medial hamstrings were recorded at 2000 Hz using a Delsys Trigno Wireless System (Boston, MA), with rectangular electrodes (sized 37mmx26mmx15mm), and a SEMG signal band-with of 20-450Hz. For normalization purposes, each subject’s maximal voluntary isometric muscle activation (MVIC) was then assessed with SEMG. Both muscle groups were tested in 60° knee flexion using a hand-held dynamometer, fixated with a belt, for a total of three repetitions of five seconds MVIC for each leg, with one minute’s rest in between each repetition. During quadriceps testing the participants were sitting while during hamstrings testing, subjects were lying prone. Standardized instructions and verbal encouragement were provided during testing.

Testing procedure

A 3-axis accelerometry inertial measurement unit was placed on the sacrum to identify foot contact and toe-off based on its acceleration signal.29 The toe-off event was defined as the maximum acceleration value prior to the flight phase and the initial foot contact was defined as the point when the acceleration exceeded 1g after the flight phase on its way to reach maximum value during the load absorption phase. The flight phase was defined where the acceleration was consistently below 1g (Appendix A). The time events from the accelerometer were finally synchronized with the SEMG signal.

Instructions for the jumping task were given immediately before the task was executed, and the participants were asked to perform a minimum of one familiarization trial (without recording) to confirm they understood the task. Participants were instructed to start the test and to hop on one leg as high as possible and as fast as possible until the test was terminated vocally by the examiner who ensured the athletes hopped at least 30 seconds. Athletes who did not hop for 30 seconds were excluded from the data (one participant from BTB group).

Data processing and statistical analysis

Data from all the hops for each subject, for each leg, were explored with a customized Matlab script for visualization and analyses of SEMG and accelerometer signal. The accelerometer data were low-pass filtered with a 5 Hz finite-impulse-response (FIR) and the SEMG signal was filtered using 8th-order band-pass filter, with high pass cut at 30Hz and low pass cut at 500Hz using Matlab (R2022a, The Mathworks Inc, Natick, MA). After this, data for each hop was extracted and normalized from one toe off to the following and presented as 101 data points (0-100%) with foot contact centered to 50%. The relative SEMG (%MVC) was then used for subsequent analysis for each of the 101 (0-100%) time points for each hop. Every hop sequence was divided into three phases based on the total hop count for that individual. Where the total number of hops was not exactly divisible by three, care was taken to ensure that the first and third phases had an identical number of hops. Separate analyses were conducted examining: the overall peak activation (magnitude and point of peak); and the relative activation patterns averaged from all hops in each of the three phases during the entire 30-second period.

Peak SEMG activation for each participant was compared between legs using linear mixed models. Distributions (including linear mixed model residuals) were examined using frequency histograms, Q-Q plots, and Shapiro Wilk testing. Descriptive statistics were then calculated, and subsequently linear mixed models for each muscle group were created for their average peak normalized SEMG with fixed (group and leg) and random (participant) effects used to identify main differences and interaction effects. Subsequent pairwise comparisons with Tukey post-hoc corrections were done for each muscle group examining peak SEMG activation across all hop phases for each patient group and leg.

For the control group, no significant differences were found comparing left and right legs so data for a single healthy leg was randomly extracted from both left and right legs for further analyses. For the patient cohort, data are presented for both their operated (“injured”) and uninjured legs.

Spatial Parametric Mapping30 (SPM) was conducted in Matlab (version: 2018a, The Mathworks Inc., Natick, USA) to compare the activation pattern of the hop cycles during the first and third hop phases. The significance level was set to p<0.05.

RESULTS

Forty-four male participants were included. Over half of the participants had undergone ACLR with a HS graft (n=24; age 22.2± 4.83 years, weight 74.9±11.87 kg, and height 178.3±9.22 cm) and the rest using BTB reconstruction (n=20; age 22.4±4.89 years, weight 72.0 ±10.58.1 kg, and height: 174.1±7.46. cm), and both groups were on average eight months (±2.8 months) post-surgery. Thirty-one injury-free male footballers (age 24.5 ± 4.23 years, weight 72.7 ± 9.49kg, height 177.1 ± 7.53 cm) were recruited as controls.All included participants were able to perform the minimum 30 seconds’ hop testing task on each leg. The number of hops completed in the 30 seconds ranged from 21 to 56 results from groups are present in Table 1.

198512 Table 1. Mean number of jumps ± standard deviation (SD) performed for the different groups and legs during the 30 seconds.

Group	BTB		HS		Controls	
Leg	Healthy	Injured	Healthy	Injured	Healthy	
Jumps	41.5±7.0	41.8±7.4	44.0±4.7	43.6±6.8	42.4±4.1	

Figures 1 and 2 show the average activation for the 1st, 2nd, and 3rd phases of the 30 seconds’ hop task. SPM analysis comparing the first and third phase of the repeated hop cycle for quadriceps activation revealed statistically significant differences in activation levels (an effective shift to earlier in the hop cycle, Figure 1) of peak vastus medialis and vastus lateralis activation in the control group, in the BTB healthy and injured, and healthy HS group. The SPM for hamstring activation revealed statistically significant differences in activation levels for lateral hamstring in all but BTB-injured group and medial hamstring in the control group only (Figure 2).

198513 Figure 1. Mean vastus lateralis (VL) and medialis (VM) activation comparison between the first (red) and the last (blue) period during the 30-second vertical hop task.

Each panel illustrates the mean for the first phase (red) second phase (dotted gray) and the last phase (blue) of the hop task. The Y-axis represents the relative muscle activation compared to maximum voluntary contraction (0-1, vertical scale truncated to 0-0.7 for clarity) and the X-axis represents the entire hop phase with foot contact at 50% (0-100) presented with dotted vertical line. Within each panel, the inset above illustrates the Statistical Parametric Mapping comparing the first and third hop periods. The thick black line depicts the test statistic continuum, which in this case is a t continuum, or “SPM{t}” The red hashed line depicts the critical threshold at alpha = 5%. From a classical hypothesis testing perspective, the null hypothesis is rejected at alpha if the SPM{t} exceeds this threshold, indicated by the shaded grey area where p<0.05. No statistical analyses were made using the 2nd period; it is shown for reference only.

198514 Figure 2. Mean lateral and medial hamstring activation comparison between the first (purple) and the last (green) period during the 30-second vertical hop task.

Each panel illustrates the mean for the first phase (purple) second phase (dotted gray) and the last phase (green) of the hop task. The Y-axis represents the relative muscle activation to maximum voluntary contraction (0-1, vertical scale truncated to 0-0.2 for clarity) and the X-axis represents the entire hop phase with foot contact at 50% (0-100) presented with dotted vertical line. Within each panel, the inset above illustrates the Statistical Parametric Mapping comparing the first and third hop periods. The thick black line depicts the test statistic continuum, which in this case is a t continuum, or “SPM{t}” The red hashed line depicts the critical threshold at alpha = 5%. From a classical hypothesis testing perspective, the null hypothesis is rejected at alpha if the SPM{t} exceeds this threshold, indicated by the shaded grey area where p<0.05. No statistical analyses were made using the 2nd period; it is shown for reference only.

Linear mixed model analysis results revealed lower peak activation levels of the vastus lateralis (p=0.001, CI 95%: 27.9 to 41.3) and vastus medialis (p=0.001, 95% CI: 39.0 to 59.6) with a main effect of leg, showing a lower activation in the injured compared to healthy legs. For lateral hamstrings there were significant between group differences (p<0.009) in peak activation with BTB lower than controls (p<0.035, 95% CI: -43.1 to -1.3) and HS lower than controls (p<0.029, 95% CI: -41.4 to -1.8) with main effect seen in healthy legs (lower) compared to injured. Linear mixed model analysis showed a significantly lower peak muscle activation in the medial hamstring with main affect seen between 1st and 3rd phase of the hop cycle in all groups (p=0.022, 95% CI: 0.6 to 10.0).

DISCUSSION

The main findings of the present study show a shift in quadriceps and hamstrings peak activation - an earlier peak activation in the hop cycle in relation to foot contact as the participants repeatedly maximally executed single leg hops for 30 seconds. This pattern for quadriceps and lateral hamstrings muscles was seen in all groups but was not statistically significant for the injured leg of the BTB group. The same pattern was seen for medial hamstrings but the shift in peak activation was only statistically significant in the control group.

The changes in activation pattern during the 30 seconds’ maximal hops may have implications for return to sport testing. The timing of peak activation of the quadriceps and hamstrings relative to foot contact likely influences tibial translation. The results demonstrated that quadriceps and hamstrings peak activation generally occurred earlier in the hop cycle, ultimately prior to foot contact, as the repeated hop cycle progresses. The authors suggest that a more complete picture of motor behavior during hopping is provided by this repeated hopping task and venture that this may be more relevant to many sporting contexts where repeated efforts are required. The authors further suggest that clinicians should be cautious in extrapolating from an isolated hop test (as is commonly performed at discharge testing31) if the aim is to understand an individual’s motor behavior during repeated hopping.

The shift in activation during the repeated hop task was only revealed through analyzing activation during the entire hop task and comparing the activation across the entire 30 seconds’ hopping. More commonly, SEMG is analyzed as a single scalar value – e.g., peak activation during the task. Examining the entire movement instead of an arbitrary point in the movement, or a single scalar such as peak activation during the entire action, may therefore allow a better appreciation of the change in motor pattern during the task. This approach may be a useful addition to existing return to sport functional testing which may ultimately shed light on risk of re-injury32 and other posttraumatic problems (pain, weakness, instability, osteoarthrosis).4,33,34

This alteration in motor pattern seen during the 30 seconds’ hopping may be in response to fatigue, tibial translation, or other factors.35,36 Researchers looking at the effect of fatigue on neuromuscular control have shown more co-contraction and higher activation in the leg muscles at contact and in ACLR athletes earlier muscle pre-activation during landing task to establish knee stability.21 In our study, despite peak activation moving closer to foot contact, repeated hopping was not associated with higher activation of the quadriceps or hamstrings, conversely in our study lower peak quadriceps activation in the ACLR leg was observed in the BTB and HS groups compared to the uninjured leg and compared to the Control group. Previously, decreased quadriceps and hamstrings activation has been reported in ACLR athletes after a sequence of fatiguing deep squats followed by a dynamic jump endurance protocol37 suggesting fatigue may be an influencing factor for this observation.

Overall, few differences in activation patterns were observed between the HS and BTB groups. In contrast, previous researchers examining a dynamic forward hop task reported increased quadriceps before landing (“pre-activation”) for the HS ACLR participants, while the BTB- graft group did not present a clear pre-activation pattern.38 The different tasks – vertical compared to horizontal hops – likely contribute to the different results.25,39 In healthy knees35 and in the ACLR knees,40 tibial anterior translation increases with quadriceps pre-activation40 and adequate hamstring activation can be important to control the translation36 while low quadriceps amplitude decreases the attenuation of landing forces.23 Fatigue is known to affect the magnitude of hamstrings activation41 which agrees with the findings of present study as the authors found a decline in medial hamstring activation from the 1st to 3rd phase of the hop cycle was present in all groups The shift in activation to earlier in the hop cycle could represent a protective strategy to minimize tibial translation through co-contraction prior to foot strike.42,43

The athletes examined in the current study had demonstrated >90% between-leg symmetry in isokinetic tests of knee flexion and extension strength. During the repeated hopping task, reduced peak activation of the quadriceps and hamstrings was observed for the ACLR leg. Previous research examining vertical and horizontal hop tasks suggests ACLR patients adopt a strategy shifting work away from their knee to their hip and ankle.25,39 While not investigated in the present study, this would plausibly explain these findings (of reduced peak activation) despite apparent adequate knee strength. Differences in muscle activation are commonly presented in ACLR male athletes during jump testing but results are mixed showing decreased,24 or increased activation.44,45 The disparities in results could be related to differences in testing i.e., cohort, protocol, and normalization methods.46

Limitations

While this research has shown alterations in activation patterns, the current research did not consider any kinematic or kinetic implications of these which now should be addressed in future research given these findings. Due to the lack of kinematic data we are unable to determine whether the changes seen in muscle activation are related to changes in kinematic or kinetics47 and/or reduced jump height.

The patients examined in this study had reached clinical discharge criteria,27 but the time taken to do so varied (5 to 12 months). The present study is not powered to examine the effect of time since surgery, and it is possible that the athletes continue to alter their neuromuscular profiles across their rehab and beyond, nevertheless differences in muscle activation have been reported 1-2 years post ACLR in functional movements.23,25

The current research included only hamstring and patellar tendon grafts, other graft choices (e.g. quadriceps tendon, allografts, artificial ligaments, etc) would likely yield different results again. It should also be noted that the control group consisted only of professional footballers while the ACLR group included professional athletes playing football, futsal, rugby, handball, and volleyball.

Conclusion

A shift in activation of the thigh muscles was shown (earlier) as the 30-second hop task progressed. EMG analysis of single hops is therefore not necessarily representative of the muscles’ activation patterns and the changes seen during repeated hops. Repeated jump and hop testing protocols that induce endurance and motor control challenges probably provide complementary information to return to sport testing which may be more relevant to many sports where repeated efforts are required.

Conflict of Interest

The authors declare no conflicts of interest.

Supplementary Material

Appendix A

Acknowledgements

The authors express their appreciation to the patients and subjects for participating in this study.

Special thanks and gratitude to the ACL rehabilitation group of Aspetar Sports Medicine Hospital Doha Qatar for the assistance in patient recruitment.
==== Refs
Patient expectations of primary and revision anterior cruciate ligament reconstruction Knee Surgery, Sports Traumatology, Arthroscopy Feucht Matthias J. Cotic Matthias Saier Tim Minzlaff Philipp Plath Johannes E. Imhoff Andreas B. Hinterwimmer Stefan Wiley 2016
24 1 201 207 0942-2056 10.1007/s00167-014-3364-z 10.1007/s00167-014-3364-z
Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors British Journal of Sports Medicine Ardern Clare L Taylor Nicholas F Feller Julian A Webster Kate E BMJ 25 8 2014
48 21 1543 1552 0306-3674 10.1136/bjsports-2013-093398 10.1136/bjsports-2013-093398
One in 5 athletes sustain reinjury upon return to high-risk sports after ACL reconstruction: A systematic review in 1239 athletes younger than 20 years Sports Health: A Multidisciplinary Approach Barber-Westin Sue Noyes Frank R. SAGE Publications 6 5 2020
12 6 587 597 1941-7381 10.1177/1941738120912846 10.1177/1941738120912846 32374646
Osteoarthritis prevalence following anterior cruciate ligament reconstruction: A systematic review and numbers-needed-to-treat analysis Journal of Athletic Training Luc Brittney Gribble Phillip A. Pietrosimone Brian G. Journal of Athletic Training/NATA 1 12 2014
49 6 806 819 1062-6050 10.4085/1062-6050-49.3.35 10.4085/1062-6050-49.3.35 25232663
Return to play, performance, and career duration after anterior cruciate ligament rupture: A case–control study in the five biggest football nations in Europe Scandinavian Journal of Medicine & Science in Sports Niederer Daniel Engeroff Tobias Wilke Jan Vogt Lutz Banzer Winfried Wiley 9 7 2018
28 10 2226 2233 0905-7188 10.1111/sms.13245 10.1111/sms.13245 29927499
Psychological, social and contextual factors across recovery stages following a sport-related knee injury: a scoping review British Journal of Sports Medicine Truong Linda K Mosewich Amber D Holt Christopher J Le Christina Y Miciak Maxi Whittaker Jackie L BMJ 14 2 2020
54 19 1149 1156 0306-3674 10.1136/bjsports-2019-101206 10.1136/bjsports-2019-101206 32060141
What is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis Sports Medicine Webster Kate E. Hewett Timothy E. Springer Science and Business Media LLC 23 3 2019
49 6 917 929 0112-1642 10.1007/s40279-019-01093-x 10.1007/s40279-019-01093-x
Limb symmetry indexes can overestimate knee function after ACL injury Journal of Orthopaedic & Sports Physical Therapy Wellsandt Elizabeth Failla Mathew J. Snyder-Mackler Lynn Journal of Orthopaedic & Sports Physical Therapy (JOSPT) 5 2017
47 5 334 338 0190-6011 10.2519/jospt.2017.7285 10.2519/jospt.2017.7285 28355978
Symmetry in triple hop distance hides asymmetries in knee function after ACL reconstruction in athletes at return to sports The American Journal of Sports Medicine Kotsifaki Argyro Van Rossom Sam Whiteley Rodney Korakakis Vasileios Bahr Roald Sideris Vasileios Smith Philip Graham Jonkers Ilse SAGE Publications 2022
50 2 441 450 0363-5465 10.1177/03635465211063192 10.1177/03635465211063192 34889652
Which assessments are used to analyze neuromuscular control by electromyography after an anterior cruciate ligament injury to determine readiness to return to sports? A systematic review BMC Sports Science, Medicine and Rehabilitation Blasimann Angela Koenig Irene Baert Isabel Baur Heiner Vissers Dirk Springer Science and Business Media LLC 8 11 2021
13 1 142 2052-1847 10.1186/s13102-021-00370-5 10.1186/s13102-021-00370-5 34749813
Altered neuromuscular activity of the lower-extremities during landing tasks in patients with anterior cruciate ligament reconstruction: A systematic review of electromyographic studies Journal of Sport Rehabilitation He Xin Leong Hio Teng Lau On Yue Ong Michael Tim-Yun Yung Patrick Shu-Hang Human Kinetics 1 11 2020
29 8 1194 1203 1056-6716 10.1123/jsr.2019-0393 10.1123/jsr.2019-0393
Long-term deficits in quadriceps strength and activation following anterior cruciate ligament reconstruction Physical Therapy in Sport Otzel Dana M. Chow John W. Tillman Mark D. Elsevier BV 2 2015
16 1 22 28 1466-853X 10.1016/j.ptsp.2014.02.003 10.1016/j.ptsp.2014.02.003
Quadriceps strength and volitional activation after anterior cruciate ligament reconstruction: A systematic review and meta-analysis Sports Health: A Multidisciplinary Approach Lisee Caroline Lepley Adam S. Birchmeier Thomas O’Hagan Kaitlin Kuenze Christopher SAGE Publications 14 1 2019
11 2 163 179 1941-7381 10.1177/1941738118822739 10.1177/1941738118822739 30638441
Deficits in quadriceps strength and patient-oriented outcomes at return to activity after ACL reconstruction: A review of the current literature Sports Health: A Multidisciplinary Approach Lepley Lindsey K. SAGE Publications 20 3 2015
7 3 231 238 1941-7381 10.1177/1941738115578112 10.1177/1941738115578112 26131300
Return to play following ACL reconstruction: a systematic review about strength deficits Archives of Orthopaedic and Trauma Surgery Petersen Wolf Taheri Pouria Forkel Phillip Zantop Thore Springer Science and Business Media LLC 5 8 2014
134 10 1417 1428 0936-8051 10.1007/s00402-014-1992-x 10.1007/s00402-014-1992-x 25091127
Quadriceps strength after anterior cruciate ligament reconstruction compared with uninjured matched controls: A systematic review and meta-analysis Orthopaedic Journal of Sports Medicine Brown Conlan Marinko Lee LaValley Michael P. Kumar Deepak SAGE Publications 1 4 2021
9 4 2325967121991534 2325-9671 10.1177/2325967121991534 10.1177/2325967121991534 33889639
Biomechanical but not strength or performance measures differentiate male athletes who experience ACL reinjury on return to level 1 sports The American Journal of Sports Medicine King Enda Richter Chris Daniels Katherine A.J. Franklyn-Miller Andy Falvey Eanna Myer Gregory D. Jackson Mark Moran Ray Strike Siobhan SAGE Publications 22 2 2021
49 4 918 927 0363-5465 10.1177/0363546520988018 10.1177/0363546520988018 33617291
Persistent neuromuscular and corticomotor quadriceps asymmetry after anterior cruciate ligament reconstruction Journal of Athletic Training Kuenze Christopher M. Hertel Jay Weltman Arthur Diduch David Saliba Susan A. Hart Joseph M. Journal of Athletic Training/NATA 1 3 2015
50 3 303 312 1062-6050 10.4085/1062-6050-49.5.06 10.4085/1062-6050-49.5.06 25622244
Contributions of neural excitability and voluntary activation to quadriceps muscle strength following anterior cruciate ligament reconstruction The Knee Lepley Adam S. Ericksen Hayley M. Sohn David H. Pietrosimone Brian G. Elsevier BV 6 2014
21 3 736 742 0968-0160 10.1016/j.knee.2014.02.008 10.1016/j.knee.2014.02.008 24618459
Timing of muscle activation is altered during single-leg landing tasks after anterior cruciate ligament reconstruction at the time of return to sport Clinical Journal of Sport Medicine Rocchi Jacopo Emanuele Labanca Luciana Laudani Luca Minganti Carlo Mariani Pier Paolo Macaluso Andrea Ovid Technologies (Wolters Kluwer Health) 11 2020
30 6 e186 e193 1050-642X 10.1097/jsm.0000000000000659 10.1097/jsm.0000000000000659
Effect of fatigue on electromyographic activity patterns of the knee joint muscles in anterior cruciate ligament reconstructed and deficient patients during landing task Journal of Functional Morphology and Kinesiology Dashti Rostami Komeil Alizadeh Mohammad H Minoonejad Hooman Yazdi Hamidreza Thomas Abbey MDPI AG 5 4 2018
3 2 22 2411-5142 10.3390/jfmk3020022 10.3390/jfmk3020022
Effects of ACL reconstruction surgery on muscle activity of the lower limb during a jump-cut maneuver in males and females Journal of Orthopaedic Research Coats-Thomas Margaret S. Miranda Daniel L. Badger Gary J. Fleming Braden C. Wiley 21 8 2013
31 12 1890 1896 0736-0266 10.1002/jor.22470 10.1002/jor.22470 23966333
Quadriceps neuromuscular function and jump-landing sagittal-plane knee biomechanics after anterior cruciate ligament reconstruction Journal of Athletic Training Ward Sarah H. Blackburn J. Troy Padua Darin A. Stanley Laura E. Harkey Matthew S. Luc-Harkey Brittney A. Pietrosimone Brian Journal of Athletic Training/NATA 1 2 2018
53 2 135 143 1062-6050 10.4085/1062-6050-306-16 10.4085/1062-6050-306-16 29350554
Asymmetry and thigh muscle coactivity in fatigued anterior cruciate ligament-reconstructed elite skiers Medicine & Science in Sports & Exercise Jordan Matthew J. Aagaard Per Herzog Walter Ovid Technologies (Wolters Kluwer Health) 1 2017
49 1 11 20 0195-9131 10.1249/mss.0000000000001076 10.1249/mss.0000000000001076
Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes British Journal of Sports Medicine Kotsifaki Argyro Rossom Sam Van Whiteley Rod Korakakis Vasileios Bahr Roald Sideris Vasileios Jonkers Ilse BMJ 8 2 2022
56 9 490 498 0306-3674 10.1136/bjsports-2021-104692 10.1136/bjsports-2021-104692 35135826
Assessment of repeated vertical jump for anaerobic exercise performance International Journal of Physical Education, Sports and Health Ha Tae Geun Lee Seung Ro Lee Su Young Ning Li Lee Do Young Ahn Jae Woong Kim Dong Su Jeon Ji Yun Park YuJin Moon Ju Hee Hurr Chansol 2020
7 3 405 409 2394-1693 publisher: AkiNik Publications
Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture British Journal of Sports Medicine Kyritsis Polyvios Bahr Roald Landreau Philippe Miladi Riadh Witvrouw Erik BMJ 23 5 2016
50 15 946 951 0306-3674 10.1136/bjsports-2015-095908 10.1136/bjsports-2015-095908
Development of recommendations for SEMG sensors and sensor placement procedures Journal of Electromyography and Kinesiology Hermens Hermie J Freriks Bart Disselhorst-Klug Catherine Rau Günter Elsevier BV 10 2000
10 5 361 374 1050-6411 10.1016/s1050-6411(00)00027-4 10.1016/s1050-6411(00)00027-4
Comparing three devices for jump height measurement in a heterogeneous group of subjects Journal of Strength and Conditioning Research Magnúsdóttir Ásdís Orgilsson Baldur Karlsson Brynjar Ovid Technologies (Wolters Kluwer Health) 10 2014
28 10 2837 2844 1064-8011 10.1519/jsc.0000000000000464 10.1519/jsc.0000000000000464
Statistical Parametric Mapping (SPM) for alpha-based statistical analyses of multi-muscle EMG time-series Journal of Electromyography and Kinesiology Robinson Mark A. Vanrenterghem Jos Pataky Todd C. Elsevier BV 2 2015
25 1 14 19 1050-6411 10.1016/j.jelekin.2014.10.018 10.1016/j.jelekin.2014.10.018
Which hop tests can best identify functional limb asymmetry in patients 9-12 months after anterior cruciate ligament reconstruction employing a hamstrings tendon autograft? International Journal of Sports Physical Therapy Ebert Jay R Du Preez Luke Furzer Bonnie Edwards Peter Joss Brendan International Journal of Sports Physical Therapy 1 4 2021
16 2 393 403 2159-2896 10.26603/001c.21140 10.26603/001c.21140 33842035
Ipsilateral graft and contralateral ACL rupture at five years or more rollowing ACL reconstruction The Journal of Bone & Joint Surgery Wright Rick W. Magnussen Robert A. Dunn Warren R. Spindler Kurt P. Ovid Technologies (Wolters Kluwer Health) 6 2011
93 12 1159 1165 0021-9355 10.2106/jbjs.j.00898 10.2106/jbjs.j.00898 21776554
The relationship between Anterior Cruciate Ligament injury and osteoarthritis of the knee Advances in Orthopedics Simon David Mascarenhas Randy Saltzman Bryan M. Rollins Meaghan Bach Bernard R. MacDonald Peter Hindawi Limited 2015
2015 e928301 2090-3464 10.1155/2015/928301 10.1155/2015/928301 25954533
Post-traumatic osteoarthritis following ACL injury Arthritis Research & Therapy Wang Li-Juan Zeng Ni Yan Zhi-Peng Li Jie-Ting Ni Guo-Xin Springer Science and Business Media LLC 24 3 2020
22 1 57 1478-6362 10.1186/s13075-020-02156-5 10.1186/s13075-020-02156-5 32209130
The effects of muscle fatigue on neuromuscular function and anterior tibial translation in healthy knees The American Journal of Sports Medicine Wojtys Edward M. Wylie Bradford B. Huston Laura J. SAGE Publications 9 1996
24 5 615 621 0363-5465 10.1177/036354659602400509 10.1177/036354659602400509 8883681
Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight-bearing flexion Journal of Orthopaedic Research MacWilliams B. A. Wilson D. R. Desjardins J. D. Romero J. Chao E. Y. S. Wiley 11 1999
17 6 817 822 0736-0266 10.1002/jor.1100170605 10.1002/jor.1100170605
Effects of neuromuscular fatigue on quadriceps strength and activation and knee biomechanics in individuals post–anterior cruciate ligament reconstruction and healthy adults Journal of Orthopaedic & Sports Physical Therapy Thomas Abbey C. Lepley Lindsey K. Wojtys Edward M. McLean Scott G. Palmieri-Smith Riann M. Journal of Orthopaedic & Sports Physical Therapy (JOSPT) 12 2015
45 12 1042 1050 0190-6011 10.2519/jospt.2015.5785 10.2519/jospt.2015.5785 26471851
Successful feed-forward strategies following ACL injury and reconstruction Journal of Electromyography and Kinesiology Bryant Adam L. Newton Robert U. Steele Julie Elsevier BV 10 2009
19 5 988 997 1050-6411 10.1016/j.jelekin.2008.06.001 10.1016/j.jelekin.2008.06.001
Young athletes with quadriceps femoris strength asymmetry at return to sport after anterior cruciate ligament reconstruction demonstrate asymmetric single-leg drop-landing mechanics The American Journal of Sports Medicine Ithurburn Matthew P. Paterno Mark V. Ford Kevin R. Hewett Timothy E. Schmitt Laura C. SAGE Publications 10 9 2015
43 11 2727 2737 0363-5465 10.1177/0363546515602016 10.1177/0363546515602016
Dynamic effect of quadriceps muscle activation on anterior tibial translation after single-bundle and double-bundle anterior cruciate ligament reconstruction Arthroscopy: The Journal of Arthroscopic & Related Surgery Tsarouhas Alexander Giakas Giannis Malizos Konstantinos N. Spiropoulos Giannis Sideris Vasilios Koutedakis Yiannis Hantes Michael E. Elsevier BV 7 2015
31 7 1303 1309 0749-8063 10.1016/j.arthro.2015.02.028 10.1016/j.arthro.2015.02.028 25882183
Gender and fatigue have influence on knee joint control strategies during landing Clinical Biomechanics Gehring Dominic Melnyk Mark Gollhofer Albert Elsevier BV 1 2009
24 1 82 87 0268-0033 10.1016/j.clinbiomech.2008.07.005 10.1016/j.clinbiomech.2008.07.005
Submaximal fatigue of the hamstrings impairs specific reflex components and knee stability Knee Surgery, Sports Traumatology, Arthroscopy Melnyk Mark Gollhofer Albert Wiley 2007
15 5 525 532 0942-2056 10.1007/s00167-006-0226-3 10.1007/s00167-006-0226-3
The significant effect of the medial hamstrings on dynamic knee stability Knee Surgery, Sports Traumatology, Arthroscopy Toor Aneet S. Limpisvasti Orr Ihn Hansel E. McGarry Michelle H. Banffy Michael Lee Thay Q. Wiley 2019
27 8 2608 2616 0942-2056 10.1007/s00167-018-5283-x 10.1007/s00167-018-5283-x
Neuromuscular and biomechanical landing performance subsequent to ipsilateral semitendinosus and gracilis autograft anterior cruciate ligament reconstruction Knee Surgery, Sports Traumatology, Arthroscopy Vairo Giampietro L. Myers Joseph B. Sell Timothy C. Fu Freddie H. Harner Christopher D. Lephart Scott M. Wiley 2008
16 1 2 14 0942-2056 10.1007/s00167-007-0427-4 10.1007/s00167-007-0427-4
Hamstring muscle activity after primary anterior cruciate ligament reconstruction—A protective mechanism in those who do not sustain a secondary injury? A preliminary study Sports Health: A Multidisciplinary Approach Palmieri-Smith Riann M. Strickland Meagan Lepley Lindsey K. SAGE Publications 13 6 2019
11 4 316 323 1941-7381 10.1177/1941738119852630 10.1177/1941738119852630 31194624
Hamstrings neuromuscular function after anterior cruciate ligament reconstruction: A systematic review and meta-analysis Sports Medicine Sherman David A. Glaviano Neal R. Norte Grant E. Springer Science and Business Media LLC 20 2 2021
51 8 1751 1769 0112-1642 10.1007/s40279-021-01433-w 10.1007/s40279-021-01433-w
Correlation of lower limb muscle activity with knee joint kinematics and kinetics during badminton landing tasks International Journal of Environmental Research and Public Health Hu Zhe Kim Youngsuk Zhang Yanan Zhang Yuxi Li Jiaying Tang Xuan Sohn Jeehoon Kim Sukwon MDPI AG 9 12 2022
19 24 16587 1660-4601 10.3390/ijerph192416587 10.3390/ijerph192416587 36554467
