Angle specific analysis of hamstrings and quadriceps isokinetic torque identify residual deficits in soccer players following ACL reconstruction: a longitudinal investigation

Improved Quadriceps Torque Production With Optimized Biofeedback in Patients After Anterior Cruciate Ligament Reconstruction

Hogg, JA, Barger, NB, Bruce, JR, White, CC, Myer, GD, and Diekfuss, JA. Improved quadriceps torque production with optimized biofeedback in patients after anterior cruciate ligament reconstruction. J Strength Cond Res XX(X): 000–000, 2024—Optimizing performance through intrinsic motivation and attention for learning: prevention rehabilitation exercise play (OPTIMAL PREP) training strategies incorporate motor learning principles to enhance movement acquisition and retention. We aimed to use OPTIMAL PREP biofeedback to evaluate its potential to improve quadriceps and hamstring torque production in patients with anterior cruciate ligament reconstruction (ACL-R). Thirteen subjects 23 ± 19 months post ACL-R completed 5 concentric quadriceps/hamstrings repetitions on an isokinetic dynamometer for each limb and counterbalanced condition at 60°·s−1. For the control condition, subjects were instructed to perform the exercise “as hard and fast as possible.” For the OPTIMAL PREP condition, subjects were additionally told that “Research shows that if you focus on moving the line on the screen (external focus) you will exhibit greater quadriceps output (enhanced expectancies)” and were given the choice of graphical representation for the biofeedback (autonomy support). Quadriceps and hamstrings peak torque, rate of force development, and torque-angle waveforms were analyzed with 2 × 2 RMANOVAs (a priori >0.06). The ACL-R limb demonstrated increased quadriceps peak torque in the OPTIMAL PREP condition than in the control condition ( = 0.13, interaction p = 0.21, pairwise Cohen's d = 0.63). Anterior cruciate ligament reconstruction limb quadriceps deficits remained near terminal extension (14–45°; peak Cohen's d = 0.57, p < 0.001). For hamstrings peak torque, we observed moderate effects for condition (OPTIMAL PREP greater; = 0.10, p = 0.29) and limb (uninvolved greater; = 0.13, p = 0.22). Easily implementable OPTIMAL PREP training strategies improved ACL-R limb quadriceps torque production, resulting in between-limb parity. However, asymmetries still existed near terminal extension.

Prediction of specific structural damage to the knee joint using qualitative isokinetic analysis

BACKGROUND

An isokinetic moment curve (IMC) pattern-damaged structure prediction model may be of considerable value in assisting the diagnosis of knee injuries in clinical scenarios. This study aimed to explore the association between irregular IMC patterns and specific structural damages in the knee, including anterior cruciate ligament (ACL) rupture, meniscus (MS) injury, and patellofemoral joint (PFJ) lesions, and to develop an IMC pattern-damaged structure prediction model.

METHODS

A total of 94 subjects were enrolled in this study and underwent isokinetic testing of the knee joint (5 consecutive flexion-extension movements within the range of motion of 90°-10°, 60°/s). Qualitative analysis of the IMCs for all subjects was completed by two blinded examiners. A multinomial logistic regression analysis was used to investigate whether a specific abnormal curve pattern was associated with specific knee structural injuries and to test the predictive effectiveness of IMC patterns for specific structural damage in the knee.

RESULTS

The results of the multinomial logistic regression revealed a significant association between the irregular IMC patterns of the knee extensors and specific structural damages ("Valley" - ACL, PFJ, and ACL + MS, "Drop" - ACL, and ACL + MS, "Shaking" - ACL, MS, PFJ, and ACL + MS). The accuracy and Macro-averaged F1 score of the predicting model were 56.1% and 0.426, respectively.

CONCLUSION

The associations between irregular IMC patterns and specific knee structural injuries were identified. However, the accuracy and Macro-averaged F1 score of the established predictive model indicated its relatively low predictive efficacy. For the development of a more accurate predictive model, it may be essential to incorporate angle-specific and/or speed-specific analyses of qualitative and quantitative data in isokinetic testing. Furthermore, the utilization of artificial intelligence image recognition technology may prove beneficial for analyzing large datasets in the future.

Rehabilitation and Return to Play Protocols After Anterior Cruciate Ligament Reconstruction in Soccer Players: A Systematic Review

BACKGROUND

Rehabilitation after anterior cruciate ligament ACL reconstruction (ACLR) is crucial for safe return to play (RTP) and reducing the chances of a reinjury. Yet, there is no consensus on the ideal functional tests to assess rehabilitation progress in soccer players after ACLR.

PURPOSE

The primary objective was to highlight the existing gap in the literature concerning the most effective standardized rehabilitation protocols and testing for facilitating successful RTP among soccer players.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review using PubMed, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted. Inclusion criteria encompassed original studies (level of evidence 1-4) that examined rehabilitation protocols, metrics of knee rehabilitation, and clinical outcomes after ACLR in soccer players.

RESULTS

This review incorporated 23 studies, predominantly retrospective case series, with a total number of 874 soccer players who underwent ACLR and rehabiliation. 5 (21.7%) studies utilized an accelerated rehabilitation protocol, while 7 (30.4%) of studies utilized a criterion-based rehabilitation. A wide heterogeneity of data was extracted including functional tests of rehabilitation and RTP such as strength test batteries, hop test batteries, and movement quality assessments. Of the 23 selected studies, 2 (8.7%) used all 3 test batteries, 8 (34.8%) used 2 test batteries, 12 (52.2%) used 1 test battery, and 1 (4.3%) used 0 of the test batteries. The mean time between surgery and RTP ranged from 3 to 8 months with only 2 (8.7%) studies reporting complications after ACLR. Lastly, out of the total studies examined, 9 (39.1%) assessed patient-reported outcome measures (PROMs), all of which demonstrated significant improvement from the initial assessment to the final follow up.

CONCLUSION

Soccer-specific rehabilitation after ACLR lacks standardization. Even though many studies have assessed protocols for optimal RTP and reduced secondary ACL injuries, there is a gap in the literature regarding the most effective protocols and RTP testing. The methodology reported by Kyritsis et al could serve as a foundation for future prospective randomized multicenter studies to establish a standard rehabilitation protocol and enable a successful return to soccer.

One-dimension statistical parametric mapping in lower limb biomechanical analysis: A systematic scoping review

BACKGROUND

Biomechanics significantly impacts sports performance and injury prevention. Traditional methods like discrete point analysis simplify continuous kinetic and kinematic data, while one-dimensional Statistical Parametric Mapping (spm1d) evaluates entire movement curves. Nevertheless, spm1d's application in sports and injury research is limited. As no systematic review exists, we conducted a scoping systematic review, synthesizing the current applications of spm1d across various populations, activities, and injuries. This review concludes by identifying gaps in the literature and suggesting areas for future research.

RESEARCH QUESTION

What research exists using spm1d in sports biomechanics, focusing on the lower limbs, in what populations, and what are the current research gaps?

METHODS

We searched PubMed, Embase, Web of Science, and ProQuest databases for the following search string: "(((knee) OR (hip)) OR (ankle)) OR (foot) OR (feet) AND (statistical parametric mapping)". English peer-reviewed studies assessing lower limb kinetics or kinematics in different sports or sports-related injuries were included. Reviews, meta-analyses, conference abstracts, and grey literature were excluded.

RESULTS

Our search yielded 165 papers published since 2012. Among these, 112 examined healthy individuals (67 %), and 53 focused on injured populations (33 %). Running (n = 45), cutting (n = 25), and jumping/landing (n = 18) were the most common activities. The predominant injuries were anterior cruciate ligament rupture (n = 21), chronic ankle instability (n = 18), and hip-related pain (n = 9). The main research gaps included the unbalanced populations, underrepresentation of common sports and sport-related injuries, gender inequality, a lack of studies in non-laboratory settings, a lack of studies on varied sports gear, and a lack of reporting standardization.

SIGNIFICANCE

This review spotlights crucial gaps in spm1d research within sports biomechanics. Key issues include a lack of studies beyond laboratory settings, underrepresentation of various sports and injuries, and gender disparities in research populations. Addressing these gaps can significantly enhance the application of spm1d in sports performance, injury analysis, and rehabilitation.

Discrete Hamstring: Quadriceps Strength Ratios Do Not Represent Angle-Specific Ratios in Premier League Soccer Players

ABSTRACT

Lunn, DE, Nicholson, G, Cooke, M, Crespo, R, Robinson, T, Price, RJ, and Walker, J. Discrete hamstring: quadriceps strength ratios do not represent angle-specific ratios in Premier League soccer players. J Strength Cond Res 37(12): 2417-2422, 2023-This study compared angle-specific hamstring:quadriceps (H:Q) ratios with their discrete counterparts during strength testing in professional male soccer players. Twenty-seven professional English Premier League soccer players were recruited for this study (age: 22 ± 4 years; stature: 1.81 ± 0.08 m; body mass: 74.7 ± 6.5 kg). Isokinetic testing of the knee flexors and extensors was conducted concentrically at two angular velocities (60° and 240°·s -1 ) and eccentrically (for the knee flexors only) at 30°·s -1 . Conventional H:Q ratio was calculated as the ratio between peak joint moment in the flexors and extensors at 60°·s -1 . Functional H:Q ratio was calculated as the peak joint moment in the flexors during the eccentric condition and the extensors at 240°·s -1 . Discrete conventional and functional H:Q ratios were 0.56 ± 0.06 and 1.28 ± 0.22, respectively. The residual differences between discrete values and angle-specific residual values were 13.60 ± 6.56% when normalized to the magnitude of the discrete value. For the functional ratios, the normalized residual was 21.72 ± 5.61%. Therefore, neither discrete ratio was representative of angle-specific ratios, although the conventional ratio had lower error overall. Therefore, practitioners should consider H:Q ratio throughout the full isokinetic range of motion, not just the discrete ratio calculated from peak joint moments, when designing and implementing training programs or monitoring injury risk, recovery from injury, and readiness to return to play.

Total Score of Athleticism: Profiling Strength and Power Characteristics in Professional Soccer Players After Anterior Cruciate Ligament Reconstruction to Assess Readiness to Return to Sport

BACKGROUND

There is no consensus on the optimal testing procedure to determine return-to-sport (RTS) readiness after anterior cruciate ligament (ACL) reconstruction. Current approaches use limb symmetry across a range of tests, but this does not consider a patient's level of athleticism or benchmarks relative to his or her noninjured counterparts.

PURPOSE

To examine the utility of the Total Score of Athleticism (TSA), a composite scale including strength, power, and reactive strength assessments, to aid RTS decision-making.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 95 professional soccer players (60 who underwent ACL reconstruction [mean age, 25.1 ± 12.6 years] and 35 who were uninjured [mean age, 23.8 ± 2.8 years]) completed a battery of tests including isokinetic knee extension and flexion torque, bilateral and unilateral countermovement jump height, relative peak power, and reactive strength index-modified. The TSA score (derived from Z scores) was calculated, and we (1) examined differences between the ACL-reconstructed and uninjured groups at the time of RTS, (2) assessed the predictive ability of the TSA to identify the player's status (ACL reconstruction vs uninjured control), and (3) included a case series to discuss the characteristics of players who sustained a subsequent injury within 4 months after RTS.

RESULTS

A large difference between the ACL-reconstructed and uninjured groups in the TSA score (d = 0.84; P < .0001) was evident. For every additional increase of 1 unit in the TSA score, the odds of belonging to the ACL-reconstructed group decreased by 74% (95% CI, 0.19-0.56). By visual inspection, the frequency of reinjured players was higher in the low (4/7) TSA tertile compared with the medium (2/7) and high (1/7) TSA tertiles.

CONCLUSION

Preliminary evidence indicates that the TSA may be a useful RTS readiness tool, as the composite score derived from strength and power measures was different in soccer players at the time of RTS after ACL reconstruction compared with healthy matched controls. There was also a higher frequency of low TSA scores in players who sustained a second injury after RTS. Therefore, it is recommended to routinely administer RTS tests encompassing strength, power, and reactive strength qualities each season across the largest possible number of players (ideally teammates).

Low Pre-Season Hamstring-to-Quadriceps Strength Ratio Identified in Players Who Further Sustained In-Season Hamstring Strain Injuries: A Retrospective Study from a Brazilian Serie A Team

A common pre-season injury prevention assessment conducted by professional football clubs is the hamstring-to-quadriceps (H:Q) strength ratio calculated by peak torque (PT). However, it is debatable whether players that present low pre-season H:Q ratios are more susceptible to further sustaining in-season hamstring strain injuries (HSI). Based upon retrospective data from a Brazilian Serie A football squad, a particular season came to our attention as ten out of seventeen (~59%) professional male football players sustained HSI. Therefore, we examined the pre-season H:Q ratios of these players. H:Q conventional (CR) and functional (FR) ratios, and the respective knee extensor/flexor PT from the limbs of players further sustaining in-season HSI (injured players, IP) were compared to the proportional number of dominant/non-dominant limbs from uninjured players (UP) in the squad. FR and CR were ~18-22% lower (p < 0.01), whereas quadriceps concentric PT was ~25% greater for IP than UP (p = 0.002). Low scores of FR and CR were correlated (p < 0.01) with high levels of quadriceps concentric PT (r = -0.66 to -0.77). In conclusion, players who sustained in-season HSI had lower pre-season FR and CR compared to UP, which appears to be associated with higher levels of quadriceps concentric torque than hamstring concentric or eccentric torque.

Hamstrings force-length relationships and their implications for angle-specific joint torques: a narrative review

Temporal biomechanical and physiological responses to physical activity vary between individual hamstrings components as well as between exercises, suggesting that hamstring muscles operate differently, and over different lengths, between tasks. Nevertheless, the force-length properties of these muscles have not been thoroughly investigated. The present review examines the factors influencing the hamstrings’ force-length properties and relates them to in vivo function. A search in four databases was performed for studies that examined relations between muscle length and force, torque, activation, or moment arm of hamstring muscles. Evidence was collated in relation to force-length relationships at a sarcomere/fiber level and then moment arm-length, activation-length, and torque-joint angle relations. Five forward simulation models were also used to predict force-length and torque-length relations of hamstring muscles. The results show that, due to architectural differences alone, semitendinosus (ST) produces less peak force and has a flatter active (contractile) fiber force-length relation than both biceps femoris long head (BFlh) and semimembranosus (SM), however BFlh and SM contribute greater forces through much of the hip and knee joint ranges of motion. The hamstrings’ maximum moment arms are greater at the hip than knee, so the muscles tend to act more as force producers at the hip but generate greater joint rotation and angular velocity at the knee for a given muscle shortening length and speed. However, SM moment arm is longer than SM and BFlh, partially alleviating its reduced force capacity but also reducing its otherwise substantial excursion potential. The current evidence, bound by the limitations of electromyography techniques, suggests that joint angle-dependent activation variations have minimal impact on force-length or torque-angle relations. During daily activities such as walking or sitting down, the hamstrings appear to operate on the ascending limbs of their force-length relations while knee flexion exercises performed with hip angles 45–90° promote more optimal force generation. Exercises requiring hip flexion at 45–120° and knee extension 45–0° (e.g. sprint running) may therefore evoke greater muscle forces and, speculatively, provide a more optimum adaptive stimulus. Finally, increases in resistance to stretch during hip flexion beyond 45° result mainly from SM and BFlh muscles.