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 < .01), whereas it remained unchanged for the reconstructed leg (P > .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 < .05) and intact leg (F = 3.36, P < .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.

Velocity at lactate threshold and running economy must also be considered along with maximal oxygen uptake when testing elite soccer players during preseason.

Maximal oxygen uptake (VO2max) 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 VO2max 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 VO2 was statistically different only between the top 2 divisions. Running economy was statistically different between divisions with similar VO2, 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 VO2max during preseason testing. Running economy may reveal differences between teams with similar VO2max.

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) microV, P > 0.05] while it increased significantly [294.2 (120.6)-317.1 (140.5) microV, 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.