Velocity at Lactate Threshold and Running Economy Must Also be Considered Along With Maximal Oxygen Uptake When Testing Elite Soccer Players During Preseason

Velocity at lactate threshold and running economy must also be considered along with maximal oxygen uptake when testing elite soccer players during preseason. J Strength Cond Res 25(2): 414-419, 2011-Maximal oxygen uptake (V̇o2max) has been traditionally used to explain physiologic differences among soccer teams of different ranking. However, other endurance markers may have greater discriminatory ability. The purpose of this study was to examine whether velocity at lactate threshold and running economy can be used to better discriminate endurance characteristics of soccer teams of different levels along with V̇o2max during preseason testing. One hundred twenty-nine professional Greek soccer players participating in the top 3 divisions underwent an incremental treadmill test to exhaustion using expired gas analysis and simultaneous blood lactate measurements. Velocity at lactate threshold was determined using the Dmax method, and running economy was measured at 12 km·h−1. Analyses of variation were used to compare for differences between divisions. Velocity at lactate threshold was the only variable that was statistically different between any 2 divisions. In every comparison, the higher division had the higher velocity at lactate threshold. The V̇o2max was statistically different only between the top 2 divisions. Running economy was statistically different between divisions with similar V̇o2max, with better running economy for the higher division in each comparison. These results indicate that velocity at lactate threshold can be used to better discriminate endurance characteristics of soccer teams of different level along with V̇o2max during preseason testing. Running economy may reveal differences between teams with similar V̇o2max

ACL reconstructed patients with a BPTB graft present an impaired vastus lateralis neuromuscular response during high intensity running

The purpose of the present study was to investigate whether the electromyographic response of the vastus lateralis (VL) muscle in the anterior cruciate ligament (ACL) reconstructed leg is similar to that of the intact contralateral leg and healthy controls, during moderate and high intensity running. Fourteen bone–patellar tendon–bone (BPTB) ACL reconstructed amateur soccer players and fourteen healthy control amateur soccer players volunteered to participate in the study. Electromyographic (EMG) traces from the vastus lateralis (VL) muscle were collected bilaterally, as athletes ran on a treadmill for 10 min on separate occasions, at moderate and high intensity. The dependent variable examined was the EMG amplitude during stance. During the moderate intensity running, EMG amplitude of the VL did not increase with time for any of the tested legs. During the high intensity running, the EMG amplitude of the VL increased significantly with time for the intact (F = 6.747, p = 0.001) and the control leg (F = 4.258, p  = 0.008), but remained unchanged for the ACL reconstructed leg. During moderate intensity running, there was no difference in the neuromuscular response of the VL in the reconstructed leg compared to the intact and control leg. High intensity running resulted in an impaired neuromuscular response of the VL in the reconstructed leg compared to the intact and control leg. It seems that potential impairments of the neuromuscular response after ACL reconstruction should be tested under high rather than moderate intensity efforts

High intensity running results in an impaired neuromuscular response in ACL reconstructed individuals

Anterior cruciate ligament (ACL) reconstruction reestablishes electromyographic activity during moderate activities such as walking but is unclear if this is also the case in sports activities such as high intensity running that results in accumulation of metabolic fatigue. Nine bone-patella tendon-bone ACL reconstructed athletes were evaluated 19.2 (5.7) months post-operatively using a telemetric electromyographic system. The neuromuscular response of vastus lateralis and biceps femoris muscles was tested bilaterally on separate occasions during 10 min running at moderate intensity (20% below the lactate threshold) and 10 min running at high intensity (40% above the lactate threshold). During moderate intensity running, electromyographic activity did not change for either leg. During high intensity running, electromyographic activity did not change for the vastus lateralis of the ACL reconstructed leg [267.8 (142.8)–263.8 (128.9) μV, P \u3e 0.05] while it increased significantly [294.2 (120.6)–317.1 (140.5) μV, P = 0.03] for the vastus lateralis of the intact leg. High intensity exercise that is associated with accumulation of metabolic fatigue, results in an impaired neuromuscular response for the vastus lateralis muscle of the ACL reconstructed leg

Follow-up Evaluation 2 Years After ACL Reconstruction With Bone–Patellar Tendon–Bone Graft Shows That Excessive Tibial Rotation Persists

Objective: To investigate in vivo if the increased tibial rotation found in anterior cruciate ligament (ACL)-deficient patients before surgery is restored 2 years after the reconstruction, during 2 high-demanding activities. Design: Prospective follow-up study. Setting: A gait analysis laboratory. Participants: Nine subjects with unilateral ACL rupture, reconstructed with a bone–patellar tendon–bone (BPTB) graft, and 10 healthy control subjects. Interventions: All the ACL-deficient patients underwent a unilateral ACL reconstruction after prereconstruction data acquisition. Main Outcome Measurements: Using a 6-camera motion analysis system, kinematics were collected as subjects (1) descended from a stair and, after foot contact, pivoted on the landing leg at 90°; and (2) jumped from a platform, landed with both feet on the ground and, after foot contact, pivoted on the right or left leg at 90° in a similar fashion. The dependent variable examined was the maximum range of motion of tibial rotation during the pivoting period. Results: For both activities, no significant differences were found between the control healthy knee and the intact knee of the patient group before and 2 years after the ACL reconstruction. Significant differences were found between the control healthy knee and the affected knee of the patients group for both activities, both before and 2 years after the ACL reconstruction. Conclusion: The increased tibial rotation found in the ACL-deficient knees was not restored with reconstruction using a BPTB graft, even 2 years postoperatively. The authors propose that this excessive tibial rotation over time may lead to further deterioration of the knee resulting from abnormal loading at areas of the cartilage that are not commonly loaded in a healthy knee

Endurance markers are related with local neuromuscular response for the intact but not for the ACL reconstructed leg during high intensity running

AIM: It has been demonstrated that the local neuromuscular response during high intensity exercise has a strong relationship with endurance markers. However, a diminished neuromuscular response has been reported for the operated leg in athletes having undergone anterior cruciate ligament reconstruction (ACLR). The purpose of the present study was to examine the relationships between endurance markers and the EMG response during high intensity running in ACLR athletes. METHODS: Fourteen ACLR soccer players underwent a GXT test to volitional exhaustion and a 10-min bout of high intensity running. During the 10-min bout, EMG data were recorded at the 3rd and 10th minute from the vastus lateralis bilaterally using a telemetric system. The final EMG levels were expressed as a percentage of the initial values. Pearson moment product correlations were used to assess the relationship between the endurance markers of VO2max, velocity at lactate threshold (vLT), velocity at 4mM (V4) and the final EMG levels. RESULTS: Final EMG levels for the intact leg had a very strong relationship with vLT (r=0.77, P=0.001) and a strong relationship with V4 (r=0.68, P=0.008). Final EMG levels for the reconstructed leg had moderate relationship with vLT (r=0.47, P=0.09) and V4 (r=0.52, P=0.06). CONCLUSION: The neuromuscular response of the intact leg during high intensity running shows strong to very strong relationships with endurance markers. Failure of the ACLR leg to present relationships of similar strength may indicate that chronic perturbations modify the ability of the local muscular environment to tolerate sustained high intensity efforts

Hamstring-Dominant Strategy of the Bone–Patellar Tendon–Bone Graft Anterior Cruciate Ligament–Reconstructed Leg Versus Quadriceps-Dominant Strategy of the Contralateral Intact Leg During High-Intensity Exercise in Male Athletes

Purpose The purpose of this study was to investigate the effect of anterior cruciate ligament (ACL) reconstruction on the quadriceps-dominant strategy as a parameter associated with the neuromuscular control of the knee joint. Methods In this study 14 competitive soccer players who had undergone ACL reconstruction with bone–patellar tendon–bone autograft and 14 healthy competitive soccer players performed two 10-minute treadmill runs, 1 at moderate intensity and 1 at high intensity. Electromyographic recordings were acquired by use of a telemetric system at the third, fifth, seventh, and tenth minute of the runs from the vastus lateralis and the biceps femoris bilaterally. The dependent variable examined was the peak electromyographic amplitude during the stance phase. Analyses of variance were used to examine significant main effects and interactions. Results Vastus lateralis electromyographic activity during high-intensity running increased for both the control leg and intact leg (F = 4.48, P \u3c .01), whereas it remained unchanged for the reconstructed leg (P \u3e .05). Biceps femoris electromyographic activity during high-intensity running increased for the reconstructed leg only compared with both the control leg (F = 3.03, P \u3c .05) and intact leg (F = 3.36, P \u3c .03). Conclusions There is no presence of the quadriceps-dominant strategy in ACL-reconstructed athletes during moderate-intensity exercise. During high-intensity exercise, the intact contralateral leg develops the quadriceps-dominant strategy whereas the reconstructed leg does not. The reconstructed leg instead increases biceps femoris activity, developing a “hamstring-dominant” strategy, and this “asymmetry” may theoretically be in favor of the reconstructed knee. Level of Evidence Level III, retrospective comparative study

The Effect of Anterior Cruciate Ligament Reconstruction on Stride-to-Stride Variability

Purpose: The purpose of our study was to investigate the functional outcome after anterior cruciate ligament (ACL) reconstruction using bone–patellar tendon– bone (BPTB) and quadrupled semitendinosus and gracilis tendon (ST/G) autografts by evaluating stride-to-stride variability. Methods: Six patients with BPTB and 6 patients with STG ACL reconstruction, 2 years postoperatively, and 6 healthy control subjects walked on a treadmill at a self-selected pace while 2 minutes of continuous kinematic data were recorded with a 6-camera optoelectronic system. Stride-to-stride variability was calculated from the knee flexion/extension data using the nonlinear measure of approximate entropy, which estimates the regularity of movement patterns over time. Results: ACL reconstruction affects stride-to-stride variability. Both the BPTB and the ST/G groups had significantly larger approximate entropy values than the healthy controls. No differences were found between the BPTB and the ST/G approximate entropy values. Conclusions: After ACL reconstruction using either BPTB or quadrupled ST/G, there is increased gait variability as compared to healthy individuals. This could be caused by the altered neuromuscular activity found in ACL-reconstructed limbs. Level of Evidence: Level III, case control study