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.     

Kinematic and electromyographic analysis in patients with patellofemoral pain syndrome during single leg triple hop test

Possible delays in pre-activation or deficiencies in the activity of the dynamic muscle stabilizers of the knee and hip joints are the most common causes of the patellofemoral pain syndrome (PFPS). The aim of the study was to compare kinematic variables and electromyographic activity of the vastus lateralis, biceps femoris, gluteus maximus and gluteus medius muscles between patients with PFPS and health subjects during the single leg triple hop test (SLTHT). This study included 14 female with PFPS (PFPS group) and 14 female healthy with no history of knee pain (Healthy group). Kinematic and EMG data ware collected through participants performed a single session of the SLTHT. The PFPS group exhibited a significant increase (p < 0.05) in the EMG activity of the biceps femoris and vastus lateralis muscles, when compared with the healthy group in pre-activity and during the stance phase. This same result was also found for the vastus lateralis muscle (p < 0.05) when analyzing the EMG activity during the eccentric phase of the stance phase. In kinematic analysis, no significant differences were found between the groups. These results indicate that biceps femoris and vastus lateralis muscles mainly during the pre-activation phase and stance phases of the SLTHT are more active in PFPS group among healthy group.     

Type of measurement used influences central and peripheral contributions to quadriceps weakness after anterior cruciate ligament (ACL) reconstruction

ObjectiveThe relative contribution of muscle size and voluntary activation (VA) on quadriceps strength after anterior cruciate ligament (ACL) reconstruction remains inconclusive. Here, we aimed to determine the contributions of muscle size and VA on quadriceps strength in ACL-reconstructed patients and determine if contributions were similar if unilateral outcomes (i.e. ACL-reconstructed limb) or the LSI was used. Design: A cross-sectional study.SettingA university research laboratory.ParticipantsSixteen individuals 6–12 months after ACL reconstruction (Age: 22.3 ± 6.0yr, Height: 1.7 ± 0.1 m, Mass: 68.7 ± 11.5 kg) were recruited.Main outcome measuresQuadriceps isometric strength and VA, via the interpolated triplet technique, were assessed bilaterally. Ultrasound images were acquired of the vastus lateralis to calculate cross-sectional area (CSA) in both legs. LSI’s were computed for all variables by expressing values of the reconstructed leg as a percent of the non-reconstructed leg. Separate stepwise linear regressions were performed to examine the contribution of VA and CSA on quadriceps strength. Model 1 used LSI for all outcomes and model 2 used outcomes from the reconstructed leg.ResultsWe observed between limb deficits of 27.78% in quadriceps strength, 13.61% in vastus lateralis CSA, and 13.18% in VA (P < 0.05). Strength LSI was significantly predicted by VA LSI (R² = 0.45, P < 0.01), but not by CSA LSI (R² = 0.01, P =0.87). Reconstructed leg strength was significantly predicted by VL CSA (R² = 0.50, P < 0.01) but not quadriceps VA (R² = 0.08, P =0.11).ConclusionsThe contributions of VA and CSA on quadriceps PT differed greatly if LSI or reconstructed leg outcomes were used. Evaluation of VA and CSA in unison may be provide a more holistic understanding of the sources of muscle weakness after ACL reconstruction.     

Fatigue after eccentric quadriceps femoris work produces earlier gastrocnemius and delayed quadriceps femoris activation during crossover cutting among normal athletic women

Athletic women are at greater risk of anterior cruciate ligament (ACL) injury than men. Twenty, healthy, athletic women were evaluated for the effect of preferred stance limb isokinetic quadriceps femoris and hamstring fatigue from eccentric work compared with controls on the activation onset of vastus medialis, rectus femoris, vastus lateralis, the medial hamstrings, biceps femoris, and gastrocnemius muscles. Following 3 weeks of crossover cut training, subjects were tested for fatigue effects (5 subjects/week, 3 conditions, 1 condition/day, order effect controlled) on muscle activation onsets prior to crossover cut landing heelstrike (mixed model, ANOVA, P < 0.05). Fatigue from eccentric quadriceps femoris work produced delayed vastus medialis (P = 0.03), rectus femoris (P = 0.007), and vastus lateralis (P = 0.03) activation onsets compared with control, but did not differ compared to hamstring fatigue. Neither hamstring nor quadriceps femoris fatigue produced differences (P > 0.05) in medial hamstring or biceps femoris activation onsets compared to control. Quadriceps femoris fatigue from eccentric work produced earlier gastrocnemius activation onsets (P = 0.048) than control, but did not differ for hamstring fatigue. The gastrocnemius appears to provide synergistic and compensatory dynamic knee stabilization in closed kinetic chain function during quadriceps femoris fatigue. This finding in a normal group at high risk of ACL injury while performing a maneuver with a high ACL injury risk supports gastrocnemius inclusion in knee rehabilitation and conditioning programs and suggests the need for comparative evaluations of knee injured/reconstructed subjects.     

Stretch reflex changes in ACL-deficient individuals and healthy controls during normal and surprise landings

No studies in ACL-D individuals have examined neuromuscular adaptations during landing from a jump where an unexpected mechanical event changes the pre-programmed course of movement. The purpose of this study was to compare pre- and post-landing muscle activation in ACL-D individuals and uninjured controls during normal and surprise landings. Nineteen ACL-D and 17 uninjured volunteered. Participants performed repeated single leg landings from 30 and 15 cm heights. During 15 cm landings, a single surprise landing was performed where participants unexpectedly fell through a false surface at 15 cm to the solid floor a further 15 cm below. Electromyography (EMG) amplitude from vastus lateralis (VL), lateral hamstrings (LH), and soleus (Sol) was recorded. Pre-landing (−60 to 0 ms), post-landing short latency (31-60 ms), and post-landing medium latency (61-90 ms) periods were examined. Comparisons in EMG amplitudes were made across limbs (ACL-D, ACL intact, and control) in 30 cm landings. Additionally, the ratio of EMG amplitude in surprise:30 cm normal landings was analyzed. Post-landing LH EMG was reduced in the ACL-D compared to control limbs at short latencies (P < 0.05). Post-landing VL EMG was reduced in the ACL-D and ACL intact compared to the control limb at both latencies (P < 0.05). Surprise landings notably increased post-landing EMG in all muscles, across all limbs (P < 0.001). However, the gain in VL EMG was significantly greater in ACL-D and ACL intact limbs (P < 0.05). These changes in neuromuscular control of ACL-D individuals during expected and surprise landings may have important implications for rehabilitation, instability, and the risk of secondary injury.     

Effects of the foot strike pattern on muscle activity and neuromuscular fatigue in downhill trail running

Minimizing musculo‐skeletal damage and fatigue is considered paramount for performance in trail running. Our purposes were to investigate the effects of the foot strike pattern and its variability on (a) muscle activity during a downhill trail run and (b) immediate and delayed neuromuscular fatigue. Twenty‐three runners performed a 6.5‐km run (1264 m of negative elevation change). Electromyographic activity of lower‐limb muscles was recorded continuously. Heel and metatarsal accelerations were recorded to identify the running technique. Peripheral and central fatigue was assessed in knee extensors (KE) and plantar flexors (PF) at Pre‐, Post‐, and 2 days post downhill run (Post2d). Anterior patterns were associated with (a) higher gastrocnemius lateralis activity and lower tibialis anterior and vastus lateralis activity during the run and (b) larger decreases in KE high‐frequency stimulus‐evoked torque Post and larger decrements in KE MVC Post2d. High patterns variability during the run was associated with (a) smaller decreases in KE Db100 Post and MVC Post2d and (b) smaller decreases in PF MVC Post and Post2d. Anterior patterns increase the severity of KE peripheral fatigue. However, high foot strike pattern variability during the run reduced acute and delayed neuromuscular fatigue in KE and PF.     

Acute and delayed peripheral and central neuromuscular alterations induced by a short and intense downhill trail run

Downhill sections are highly strenuous likely contributing to the development of neuromuscular fatigue in trail running. Our purpose was to investigate the consequences of an intense downhill trail run (DTR) on peripheral and central neuromuscular fatigue at knee extensors (KE) and plantar flexors (PF). Twenty‐three runners performed a 6.5‐km DTR (1264‐m altitude drop) as fast as possible. The electromyographic activity of vastus lateralis (VL) and gastrocnemius lateralis (GL) was continuously recorded. Neuromuscular functions were assessed Pre‐, Post‐, and 2‐day Post‐DTR (Post2d). Maximal voluntary torques decreased Post (～ ?19% for KE, ～ ?25% for PF) and Post2d (～ ?9% for KE, ～ ?10% for PF). Both central and peripheral dysfunctions were observed. Decreased KE and PF voluntary activation (VA), evoked forces, VL M‐wave amplitude, and KE low‐frequency fatigue were observed at Post. Changes in VL M‐wave amplitude were negatively correlated to VL activity during DTR. Changes in PF twitch force and VA were negatively correlated to GL activity during DTR. The acute KE VA deficit was about a third of that reported after ultramarathons, although peripheral alterations were similar. The prolonged force loss seems to be mainly associated to VA deficit likely induced by the delayed inflammatory response to DTR‐induced ultrastructural muscle damage.     

The effect of knee brace on coordination and neuronal leg muscle control: an early postoperative functional study in anterior cruciate ligament reconstructed patients

Two studies were carried out after anterior cruciate ligament (ACL) reconstruction to determine the effect of a knee brace on coordination (test 1) and electromyographic muscle activity in drop jumps (test 2). Test 1 studied 25 patients with ACL reconstruction under three test conditions (one-leg static, two-legged static, two-legged dynamic) compared with a control (n=30). The results showed highly significant improvements in all braced conditions. In test 2 ten patients with ACL reconstruction and ten healthy subjects performed a two-legged drop-jump; this was repeated 15 times and again 15 times with a knee brace worn on the reconstructed limb. Changes in electromyographically determined muscle activity (vastus medialis, vastus lateralis, biceps femoris, gastrocnemius) were observed, but they were significant in only few cases because of high variability. Drop-jumps with knee brace improved jumping height, increased the maximum knee angle in the ground contact phase, and reduced the maximum knee angle in the landing phase. Patients thus develop an increased confidence in the stability of their knees. We conclude that the benefits of the knee brace are due to the mechanical action, an enhanced coordination, and a psychological effect.     

Effect of tunnel position for anatomic single-bundle ACL reconstruction on knee biomechanics in a porcine model

Attention has been focused on the importance of anatomical tunnel placement in anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle (SB) ACL reconstruction on knee kinematics. Ten porcine knees were used for the following reconstruction techniques: three different anatomic SB [AM–AM (antero-medial), PL–PL (postero-lateral), and MID–MID] (n = 5 for each group), conventional SB (PL–high AM) (n = 5), and anatomic double-bundle (DB) (n = 5). Using a robotic/universal force–moment sensor testing system, an 89 N anterior load (simulated KT1000 test) at 30, 60, and 90° of knee flexion and a combined internal rotation (4 N m) and valgus (7 N m) moment (simulated pivot-shift test) at 30 and 60° were applied. Anterior tibial translation (ATT) (mm) and in situ forces (N) of reconstructed grafts were calculated. During simulated KT1000 test at 60° of knee flexion, the PL–PL had significantly lower in situ force than the intact ACL (P < 0.01). In situ force of the MID–MID was higher than other SB reconstructions (at 30°: 94.8 ± 2.5 N; at 60°: 85.2 ± 5.3 N; and 90°: 66.0 ± 8.7 N). At 30° of knee flexion, the PL–high AM had the lowest in situ values (67.1 ± 19.3 N). At 60 and 90° of knee flexion the PL–PL had the lowest in situ values (at 60°: 60.8 ± 19.9 N; 90°: 38.4 ± 19.2 N). The MID–MID and DB had no significant in situ force differences at 30 and 60° of knee flexion. During simulated pivot-shift test at 60° of knee flexion, the PL–PL and PL–high AM reconstructions had a significant lower in situ force than the intact ACL (P < 0.01). During simulated KT1000 test at 30, 60, and 90° of knee flexion, the PL–PL and PL–high AM had significantly lower ATT than the intact ACL (P < 0.01). During simulated KT1000 test at 60 and 90°, the MID–MID, AM–AM, and DB had significantly lower ATT than the ACL deficient knee (P < 0.01). During simulated KT1000 test at 90°, every reconstructed knee had significantly higher ATT than the intact knee (P < 0.01). In conclusion, the MID–MID position provided the best stability among all anatomic SB reconstructions and more closely restored normal knee kinematics.     

Augmentation technique for partial ACL ruptures using semitendinosus tendon in the over-the-top position

The aim of this study is to present a surgical augmentation technique for partial ACL ruptures in which an isolated, autologous, double-bundle semitendinosus tendon graft is passed over the top of the femur, thus fully preserving the still-intact fibers of the ligament remnant. Between 1992 and 2006, 24 patients underwent ACL semitendinosus autograft reconstruction and were followed up for at least 2 years. The median follow-up was 6.2 years (2–15.6). At the last follow-up examination, the patients were evaluated using the International Knee Documentation Committee scale. Subjective and functional parameters were assessed using the Tegner activity scale and the Lysholm scale. Instrumental evaluation was carried out using the KT-1000 instrument. Sixteen of the 24 patients achieved an IKDC score of A. Of the remaining eight patients, six achieved an IKDC score of B, one an IKDC score of C, and one an IKDC score of D. According to the Tegner activity scale, the median pre-injury sports activity level was seven (5–9) and the median post-injury level was six (4–9), while the mean Lysholm scale score was 95 (90–100). Clinical and biomechanical studies have shown that reconstruction techniques that address both bundles of the ACL provide better rotational stability than techniques that address only a single bundle. Therefore, it seems logical than in patients with a partial rupture of the ACL, the intact bundle could be preserved and only the torn bundle would need to be reconstructed.     

Muscle activation and the slow component rise in oxygen uptake during cycling

PURPOSE: During constant-rate high-intensity exercise, a steady state for oxygen uptake (VO2) is not achieved and, after the initial rapid increase, VO2 continues to increase slowly. The mechanism underlying the slow-component rise in VO2 during high-intensity exercise is unknown. It has been hypothesized that increased muscle use may be a contributing factor, but only limited electromyograph (EMG) data are available supporting this hypothesis. The purpose of this study was to determine whether there is an association between the VO2 slow component and muscle use assessed by contrast shifts in magnetic resonance images (magnetic resonance imaging (MRI)). METHODS: The VO2 slow component was measured in 16 subjects during two 15-min bouts of cycling performed at high and low intensities. EMG and MRI transverse relaxation times (T2) were obtained after 3 and 15 min to determine muscle activity at each intensity. RESULTS: Low-intensity cycling produced no VO2 slow component, and no increases in muscle activity, except for a small increase (P < 0.05) in the T2 of the vastus lateralis. During high-intensity cycling, VO2, T2 of the vastus lateralis, rectus femoris and whole leg, and EMG activity and median power frequency of the vastus lateralis rose significantly (P < 0.05) from 3 to 15 min. Percent increases in VO2 and muscle T2 were related during high-intensity cycling (r = 0.63), but not during low-intensity cycling (r = 0.00). CONCLUSION: We conclude that increased muscle use is in part responsible for the slow component rise in oxygen uptake. The results support the hypothesis that during constant-rate exercise at intensities above lactate threshold, progressively greater use of fast-twitch motor units increases energy demand and causes concomitant progressive increases in VO2 and lactate.     

Détermination de l'insulin-like growth factor-I, du lactate et du glucose par microdialyse musculaire au cours d'un exercice d'électrostimulation modéré

Introduction. – The impact of low intensity light neuromuscular electrostimulation (14 Hz, 30 mA) of the vastus lateralis was assessed through interstitial microdialysis measurement of free Insulin-Like Growth Factor-I, glucose and lactate during the stimulation (45 minutes) and recovery (40 minutes) periods in 3 healthy subjects.Results. – Muscular uptake of glucose was immediate, while delayed decrease of lactate production was observed. Free Insulin-Like Growth Factor-I was decreased during recovery.Conclusion. – These data suggest that a low intensity of neuromuscular electrostimulation determines a metabolic activation of the muscle. That activation spreads to the recovery period.     

The effects of ACL injury on lower extremity activation during closed kinetic chain exercise

AIM: Injury to the anterior cruciate ligament (ACL) has been suggested to alter the neuromuscular mechanism in the lower extremity. However, conclusive evidence regarding this occurrence has yet to be established during closed kinetic chain exercise. The purpose of this study was to assess differences in muscle activation during slideboard exercise between non-injured, ACL deficient, and ACL reconstructed individuals. METHODS: Experimental design: comparative study. Setting: research laboratory. Participants: subjects for this study included 10 healthy, non-injured (NI) individuals, 7 uni-lateral ACL deficient (ACLD) individuals, and 6 uni-lateral ACL reconstructed (ACLR) individuals. Interventions: EMG activity was measured from the vastus medialis (VM), vastus lateralis (VL), medial hamstring (MH), lateral hamstring (LH), tibialis anterior (TA), and medial gastrocnemius (MG) muscles during slideboard performance. Measures: EMG for each muscle during each of 6 phases of 1 average slideboard cycle was expressed as a percentage of EMG during a maximal voluntary contraction. RESULTS: The results demonstrated that during slideboard phase I the VM, VL, and TA muscles generated the greatest amount of activity as compared to the other muscles. Vastus medialis muscle activation was found to be significantly higher than the other muscles in the involved/dominant limb, as compared to the non-involved/non-dominant limb during slideboard phase II. During slideboard phases III-VI, tibialis anterior muscle activation was found to be consistently higher than the other muscles, while hamstring muscle activity was consistently the lowest. CONCLUSION: It is concluded that adaptive changes following ACL injury during a dynamic, closed kinetic chain activity such as the slideboard exercise, may be a restoration of a bi-lateral balance in muscle activation.     

The resident’s ridge as an arthroscopic landmark for anatomical femoral tunnel drilling in ACL reconstruction

The purposes of this study were to establish the technique to arthroscopically identify the resident’s ridge without bony notchplasty even in patients with chronic ACL insufficiency and to elucidate if the ridge could be used as a landmark for anatomical femoral tunnel for ACL graft. There were 50 consecutive patients undergoing arthroscopic ACL reconstruction. With the thigh kept horizontal using a leg holder, a meticulous effort was made to find out a linear ridge running proximo-distal in a posterior one-third of the lateral notch wall, after removal of superficial soft tissue with radiofrequency energy. If the ridge was found, a socket with a rectangular aperture of 5 × 10 mm was created just behind the ridge. At 3–4-weeks post surgery, three-dimensional computed tomography (3-D CT) was performed to geographically identify the location of the ridge using the socket as a reference. Arthroscopically, a linear ridge running from superior-anterior to inferior-posterior on the lateral notch wall was consistently observed 7–10 mm anterior to the posterior articular cartilage margin of the lateral femoral condyle in all of the patients. The 3-D CT pictures proved the arthroscopically identified ridge to be the resident’s ridge. The resident’s ridge is arthroscopically identifiable after non-mechanical removal of the soft tissues without bony notchplasty. The ridge is a useful landmark for anatomical femoral tunnel drilling in arthroscopic ACL reconstruction.     

Biarticular leg muscles and links to running economy

Relationships between an index of running economy (VO2 per distance) and the temporal electromyographic characteristics of leg muscles were quantified in female runners. Sixteen women performed a 30-min treadmill run at a speed designed to elicit a hard rating of perceived of exertion. Near the end of the run, oxygen uptake, video, and electromyographic data were collected simultaneously. Measures of muscle on-time durations, and on-time coactivation durations were calculated from the following muscles: gastrocnemius, vastus lateralis, rectus femoris, and biceps femoris. Nonparametric correlations between VO2 per distance and temporal electromyographic data were evaluated. Greater on-time duration of rectus femoris during stance, and greater on-time coactivation duration of rectus femoris-gastrocnemius during stance were significantly associated with more economical runners (i.e., lower VO2 per distance). The coactivation of biarticular leg muscles during stance is clearly linked to running economy and this control strategy may elicit greater elastic energy return.     

VO2 slow component correlates with vastus lateralis de-oxygenation and blood lactate accumulation during running.

BACKGROUND: In the present study, vastus lateralis de-oxygenation was monitored contemporarily with VO2 changes along a severe constant intensity running exercise, after the 3rd min up to volitional exhaustion. Blood lactate accumulation was also measured before, during and after running. METHODS: Eleven male amateur soccer players volunteered for the study. Subjects mean age, height, and body weight were 22.9+/-2 yrs, 177.5+/-6.2 cm, 71.7+/-4 kg, respectively. Measurements were carried out during running on a treadmill. Ventilatory and gas exchange parameters were measured at the mouth on a breath-by-breath basis. For blood lactate concentration accumulation measurement, capillary blood samples were taken from the fingertip. The oxygenation of the vastus lateralis muscle were measured by a continuous wave NIRS portable instrument. By means of two pretests the onset of [La]b accumulation and its associated velocity (vOBLA), and the peak of oxygen uptake and its associated velocity (vVO2,peak) were assessed. The test consisted of running on the treadmill up to volitional exhaustion at a constant velocity corresponding to vOBLA plus 50% of the difference between vVO2,peak and vOBLA (v50%Delta). RESULTS: The principal finding of this study was that vastus lateralis de-oxygenation changes measured during running correlate with a) oxygen uptake changes between the 3rd min of exercise and the time corresponding to the subject's volitional exhaustion; b) blood lactate concentration increments measured at the 3rd and the 6th min of exercise and at the time corresponding to the subject's volitional exhaustion. CONCLUSIONS: In conclusion, the results of the present study support our hypothesis that the vastus lateralis de-oxygenation contributes consistently to the VO2 slow component development in running.     

Electromyographic adjustments during continuous and intermittent incremental fatiguing cycling

We studied the sensitivity of electromyographic (EMG) variables to load and muscle fatigue during continuous and intermittent incremental cycling. Fifteen men attended three laboratory sessions. Visit 1: lactate threshold, peak power output, and VO_2max. Visits 2 and 3: Continuous (more fatiguing) and intermittent (less fatiguing) incremental cycling protocols [20%, 40%, 60%, 80% and 100% of peak power output (PPO)]. During both protocols, multichannel EMG signals were recorded from vastus lateralis: muscle fiber conduction velocity (MFCV), instantaneous mean frequency (iMNF), and absolute and normalized root mean square (RMS) were analyzed. MFCV differed between protocols (P < 0.001), and only increased consistently with power output during intermittent cycling. RMS parameters were similar between protocols, and increased linearly with power output. However, only normalized RMS was higher during the more fatiguing 100% PPO stage of the continuous protocol [continuous–intermittent mean difference (95% CI): 45.1 (8.5% to 81.7%)]. On the contrary, iMNF was insensitive to load changes and muscle fatigue (P = 0.14). Despite similar power outputs, continuous and intermittent cycling influenced MFCV and normalized RMS differently. Only normalized RMS was sensitive to both increases in power output (in both protocols) and muscle fatigue, and thus is the most suitable EMG parameter to monitor changes in muscle activation during cycling.     

Aerobic and anaerobic work capacities and leg muscle characteristics in elite orienteers

Aerobic and anaerobic work capacities, leg muscle structure and metabolic characteristics of m. vastus lateralis (NT), m. rectus femoris (RG) and mm. gastrocnemii (NT and RG) were analysed in five male and seven female elite orienteers from the Swedish National team (NT) and a reference group (RG) of eight male and 10 female upcoming orienteers, all in optimal shape at the end of a competitive season. Maximal oxygen uptake was 78.4 mlikgimin for NT men (range 75–81) and 67.8 ml/kg/min for NT women (range 62–71), for both groups significantly higher ( P <0.001) than for RG. Maximal serum lactate was 13.3 mmol/l for NT men (range 10–17) and 11.7 mmol/l for NT women (range 8.4–14), which did not differ from RG. No significant correlation was found between maximal oxygen uptake and maximal serum lactate. For NT females only maximal oxygen uptake was significantly related to running economy ( P <0.01). Muscle biopsies showed a high content of type I fibres in m. vastus lateralis as well as in m. gastrocnemius mediale. M. vastus lateralis (NT) had a higher proportion of type I fibres, capillaries per fibre as well as CS, HAD and LDH 1–2 enzymes compared with m. rectus femoris (RG) ( P <0.01–<0.001), the latter muscle showing a more anaerobic profile. NT males and females had a higher metabolic potential in m. gastrocnemius mediale than RG ( P <0.001). Our results reflect an obligate high and narrow range of aerobic and anaerobic work capacities for successful performance in international elite orienteering. It remains to be shown how these laboratory data are related to individual performance in authentic orienteering competitions.     

The role of anterior cruciate ligament reconstruction in the older patients, 55 years or above

Anterior cruciate ligament (ACL) deficiency can result in symptomatic functional instability of the knee regardless of the patient’s age. We reviewed a single surgeon database of 908 ACL reconstructions carried out in the last 20 years for symptomatic instability. 14 patients were identified who were 55 years or above at surgery (mean: 60 years, range 55–75 years). Patients were evaluated clinically and with clinical outcome scoring and KT-1000 arthrometry assessment. 12 patients (86%) were available to attend for follow-up at a mean 9 years after ACL reconstruction. The median pre-injury Tegner score was 5.5 (range 1–7) and the median pre-operative Lysholm score was 33 (range 15–67). Initially, one patient had a good result but subsequently the patient undergone total knee replacement 5 years after ACL reconstruction. For the remainder, at the most recent review, the median Lysholm score had improved to 79 (range 43–100, P < 0.05) although it had deteriorated from the maximum achieved post-op score of 85.5 (range 53–100, P < 0.05); and the Tegner score had declined to 3 (range 1–5, P < 0.05). KT-1000 testing demonstrated a mean side-to-side difference improvement in laxity from 4.6 ± 1.3 mm (range 3–7) to 1.5 ± 1.2 mm (range 0–4, P < 0.05) and >2 mm difference in only one knee (for which it was known that the graft had failed at 11 years after ACL reconstruction). At review, the same knee was the only one that demonstrated a pivot shift. ACL reconstruction with autograft in the above-55 patient with minimal osteoarthritis is a safe procedure that returns stability to the knee and permits a return to a reasonable level of activity.     

Adaptations of gait and muscle activation in chronic ACL deficiency

The purpose was to investigate whether deviations in gait parameters or muscular activity patterns can be detected in the injured and healthy leg of chronic ACL-deficient subjects. Sixteen medium-level active chronic ACL-deficient patients classified as “copers” (injury duration: 12–240 months, age 17–52 years) and 15 healthy subjects (age 20–33 years) walked at self-selected speed along a 10-m runway with a level force-plate. Gait specific data, ground reaction forces, knee and ankle angles, and EMG were documented. Knee laxity was increased and the functional scores (Lysholm, KOOS) decreased in the ACL- deficient subjects, whereas the Tegner activity level score was normal. Gait speed, stride length and stance time did not differ between ACL-deficient subjects and controls. Ground reaction forces (magnitude and times), as well as knee and ankle angles at selected points during stance and swing phases were normal in the ACL-deficient subjects compared to controls. The total duration of m. tibialis anterior (TA) activity was longer in ACL-deficient subjects than in controls (ACL-deficient injured leg vs. controls, P < 0.05). In addition, the onset of lateral gastrocnemius (LG) muscle activity occurred earlier in ACL-deficient patients (P < 0.03), resulting in a TA-LG cocontraction in the ACL-deficient but not in the control group. In conclusion, chronic, medium-level active ACL-deficient patients showed abnormalities in muscular activity patterns during gait compared to control subjects, whereas there were no detectable changes in ground reaction forces and 3D kinematic data. As the aberrant muscular activity pattern may be of importance for an even gait, it is proposed that EMG recordings may give additional information in the evaluation and rehabilitation of gait when the ACL is absent.