Jesper Bencke

Identification of Athletes at Future Risk of Anterior Cruciate Ligament Ruptures by Neuromuscular Screening

Background A high percentage of female athletes who sustain an anterior cruciate ligament (ACL) rupture suffer serious long-term consequences such as osteoarthritis and disability. Thus, identification of risk factors has high clinical relevance in the prevention of ACL rupture. Hypothesis Noninjured athletes with low knee flexor electromyography (EMG) preactivity and high knee extensor EMG preactivity during sidecutting are at increased risk of future ACL rupture. Study Design Cohort study (prognosis); Level of evidence, 2. Methods Fifty-five elite female athletes (team handball and soccer) aged 24 ± 5 years with no history of ACL injury were tested for EMG preactivity of vastus lateralis and medialis, rectus femoris, semitendinosus, and biceps femoris during a standardized side-cutting maneuver. The incidence of ACL ruptures was registered in the following 2 match seasons. Results During the subsequent 2 match seasons, 5 athletes sustained a confirmed noncontact ACL rupture. Before injury, all 5 players displayed a neuromuscular pattern that differed from the noninjured players, characterized by reduced EMG preactivity for the semitendinosus (ST) and elevated EMG preactivity for the vastus lateralis (VL) (P < .01). On the basis of these findings, a high-risk zone was defined as one standard deviation above the mean VL-ST difference. In our population, 5 of 10 subjects with a VL-ST difference in this zone sustained an ACL injury during the study period. Conclusion In the present study, currently noninjured female athletes with reduced EMG preactivity of the ST and increased EMG preactivity of the VL during side cutting were at increased risk of future noncontact ACL rupture. Our data indicate that a high-risk zone can be used to identify noninjured players at high risk of future ACL rupture. Consequently, individual preventive efforts can be introduced in time. However, large prospective studies are needed to confirm this finding before definitive clinical recommendations can be made.

The effects of neuromuscular training on knee joint motor control during sidecutting in female elite soccer and handball players.

Objective:The project aimed to implement neuromuscular training during a full soccer and handball league season and to experimentally analyze the neuromuscular adaptation mechanisms elicited by this training during a standardized sidecutting maneuver known to be associated with non-contact anterior cruciate ligament (ACL) injury. Design:The players were tested before and after 1 season without implementation of the prophylactic training and subsequently before and after a full season with the implementation of prophylactic training. Participants:A total of 12 female elite soccer players and 8 female elite team handball players aged 26 ± 3 years at the start of the study. Intervention:The subjects participated in a specific neuromuscular training program previously shown to reduce non-contact ACL injury. Methods:Neuromuscular activity at the knee joint, joint angles at the hip and knee, and ground reaction forces were recorded during a sidecutting maneuver. Neuromuscular activity in the prelanding phase was obtained 10 and 50 ms before foot strike on a force plate and at 10 and 50 ms after foot strike on a force plate. Results:Neuromuscular training markedly increased before activity and landing activity electromyography (EMG) of the semitendinosus (P < 0.05), while quadriceps EMG activity remained unchanged. Conclusions:Neuromuscular training increased EMG activity for the medial hamstring muscles, thereby decreasing the risk of dynamic valgus. This observed neuromuscular adaptation during sidecutting could potentially reduce the risk for non-contact ACL injury.

Loss of Knee-Extension Strength Is Related to Knee Swelling After Total Knee Arthroplasty

OBJECTIVE To examine whether changes in knee-extension strength and functional performance are related to knee swelling after total knee arthroplasty (TKA). DESIGN Prospective, descriptive, hypothesis-generating study. SETTING A fast-track orthopedic arthroplasty unit at a university hospital. PARTICIPANTS Patients (N=24; mean age, 66y; 13 women) scheduled for primary unilateral TKA were investigated 1 week before surgery and on the day of hospital discharge 2.4 days postsurgery. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES We assessed all patients for knee-joint circumference, knee-extension strength, and functional performance using the Timed Up & Go, 30-second Chair Stand, and 10-m fast speed walking tests, together with knee pain during all active test procedures. RESULTS All investigated variables changed significantly from pre- to postsurgery independent of knee pain. Importantly, knee circumference increased (knee swelling) and correlated significantly with the decrease in knee-extension strength (r=-.51; P=.01). Reduced fast-speed walking correlated significantly with decreased knee-extension strength (r=.59; P=.003) and decreased knee flexion (r=.52; P=.011). Multiple linear regression showed that knee swelling (P=.023), adjusted for age and sex, could explain 27% of the decrease in knee-extension strength. Another model showed that changes in knee-extension strength (P=.009) and knee flexion (P=.018) were associated independently with decreased performance in fast-speed walking, explaining 57% of the variation in fast-speed walking. CONCLUSIONS Our results indicate that the well-known finding of decreased knee-extension strength, which decreases functional performance shortly after TKA, is caused in part by postoperative knee swelling. Future studies may look at specific interventions aimed at decreasing knee swelling postsurgery to preserve knee-extension strength and facilitate physical rehabilitation after TKA.

Foot Medial Longitudinal-Arch Deformation During Quiet Standing and Gait in Subjects with Medial Tibial Stress Syndrome

The objective of this study was to investigate (1) if subjects with medial tibial stress syndrome demonstrate increased navicular drop and medial longitudinal-arch deformation during quiet standing and gait compared with healthy subjects, and (2) the relationship between medial longitudinal-arch deformation during quiet standing and gait. Thirty subjects aged 20 to 32 years were included (15 with medial tibial stress syndrome and 15 controls). Navicular drop and medial longitudinal-arch deformation were measured during quiet standing with neutral and loaded foot using a ruler and digital photography. Medial longitudinal-arch deformation was measured during walking gait using 3-dimensional gait analysis. Subjects with medial tibial stress syndrome demonstrated a significantly larger navicular drop (mean +/- 1 SD, 7.7 +/- 3.1 mm) and medial longitudinal-arch deformation (5.9 +/- 3.2 degrees) during quiet standing compared with controls (5.0 +/- 2.2 mm and 3.5 +/- 2.6 degrees, P < .05). Subjects with medial tibial stress syndrome also demonstrated significantly larger medial longitudinal-arch deformation (8.8 +/- 1.8 degrees) during gait compared with controls (7.1 +/- 1.7 degrees, P = .015). There was no correlation between medial longitudinal-arch deformation during quiet standing and gait in either of the 2 groups (r < 0.127, P > .653). The subjects with medial tibial stress syndrome in this study demonstrated increased navicular drop and medial longitudinal-arch deformation during quiet standing and increased medial longitudinal-arch deformation during gait compared to healthy subjects. Medial longitudinal-arch deformation during quiet standing did not correlate with medial longitudinal-arch deformation during gait in either of the 2 groups. ACFAS Level of Clinical Evidence: 5.

Body proportions, body composition and pubertal development of children in competitive sports

The aim of this study was primarily to investigate anthropometric variables, body composition and pubertal development in children aged 9–13 participating in competitive sports. Secondly, the influence of age, sport, training hours and pubertal development/maternal menarcheal age on body composition and pubertal development was explored. A total of 183 (96 girls, 87 boys) children performing swimming (Sw), tennis (Te), European team handball (TH), and gymnastics (Gy) took part in the study. Anthropometric measurements and pubertal development were determined. The participants completed a questionnaire regarding hours of training per week and maternal menarcheal age. Significant differences in stature (z‐scores) were found in both boys (Sw=0.06; Te=0.04; TH=0.05; Gy=−0.66, P<0.004) and girls (Sw=0.12; Te=0.19; TH=0.25; Gy=−0.96, P<0.004). In girls, sum of skinfolds in millimetres (Sw=33.4; Te=33.3; TH=41.0; Gy=27.2, P<0.02) and body mass index z‐scores (SW=0.00; Te=−0.27; TH=0.35; Gy=−0.25, P<0.001) were different between the sports. A regression analysis revealed that in girls, age and maternal menarcheal age were significantly associated with pubertal development (P<0.005 and P<0.01), respectively, and sport was associated with the sum of skinfolds (P<0.05). In boys, only age was significantly associated with pubertal development (P<0.005). In conclusion, anthropometric and body composition differences exist in athletes of both sexes from different sports but are more evident in females. Most importantly, we did not find any effect of training on body composition or pubertal development, confirming previous data that children in competitive sports are selected due to constitutional factors.

Is prepubertal growth adversely affected by sport

PURPOSE To study the effect of genetic factors, birth weight, early childhood growth, sport, hours of training, and pubertal status on the stature and body mass index (BMI) of children aged 9-13 participating in sports at a competitive level. METHODS A total of 184 children (96 girls, 88 boys), competing in swimming, tennis, team handball, and gymnastics, were investigated, assessing their height, weight, pubertal development, and BMI. Of these, 137 (76 girls, 61 boys) returned a questionnaire, which enabled us to determine height and BMI at age 2-4, birth weight, and parental heights. RESULTS Significant differences in standard deviation scores (SDS) for actual height and for height at age 2-4 were found in both sexes between the four sports. In girls, BMI SDS was significantly different between the four sports, whereas no difference was found in boys. Each sport investigated separately showed no change in height SDS and BMI SDS between ages 2-4 and 9-13. A regression analysis showed that target height, height at age 2-4, and pubertal status had a significant impact on actual height. Interestingly, the type of sport and hours of training per week had no effect on height SDS. In boys, BMI at age 2-4 and pubertal status had a significant effect on actual BMI, whereas in girls, only BMI at age 2-4 was significant. CONCLUSIONS The results suggest that prepubertal growth is not adversely affected by sport at a competitive level and that constitutional factors are of importance for choice of sport in children.

Intra-rater repeatability of the Oxford foot model in healthy children in different stages of the foot roll over process during gait

BACKGROUND The repeatability of the Oxford foot model has been reported, but possible variations in the repeatability during the foot roll over process have not been examined. The aim of this study was to determine the relative and absolute repeatability of the model for each stage of the foot roll over process during gait and to compare foot kinematic data from this study with that from another centre as a preliminary examination of the models inter-centre repeatability and validity. METHOD Eight healthy children were tested twice at the gait laboratory. Foot kinematics from this study were plotted against those from an earlier repeatability study and repeatability statistics calculated for the three rockers of stance phase and swing phase. RESULTS Foot kinematics from this study and an earlier repeatability study produced similar kinematic patterns and joint angle ranges, but there were offsets in the absolute joint angles in the frontal and transverse planes. Relative and absolute repeatability were best in the sagittal plane (flexion/extension) with the poorest repeatability in the transverse plane (rotation and abduction/adduction). There was little difference in repeatability between the three rockers. Typical error of measurement varied between planes and segments from 0.9 degrees for maximum forefoot dorsiflexion in second rocker to 8.6 degrees for maximum hindfoot internal rotation in first rocker. DISCUSSION Repeatability varied markedly between planes and segments but was consistent throughout the gait cycle. Further studies are needed to determine the inter-centre repeatability and validity of the model.

Acute fatigue impairs neuromuscular activity of anterior cruciate ligament‐agonist muscles in female team handball players

In sports, like team handball, fatigue has been associated with an increased risk of anterior cruciate ligament (ACL) injury. While effects of fatigue on muscle function are commonly assessed during maximal isometric voluntary contraction (MVC), such measurements may not relate to the muscle function during match play. The purpose of this study was to investigate the effect of muscle fatigue induced by a simulated handball match on neuromuscular strategy during a functional sidecutting movement, associated with the incidence of ACL injury. Fourteen female team handball players were tested for neuromuscular activity [electromyography (EMG)] during a sidecutting maneuver on a force plate, pre and post a simulated handball match. MVC was obtained during maximal isometric quadriceps and hamstring contraction. The simulated handball match consisted of exercises mimicking handball match activity. Whereas the simulated handball match induced a decrease in MVC strength for both the quadriceps and hamstring muscles (P<0.05), a selective decrease in hamstring neuromuscular activity was seen during sidecutting (P<0.05). This study shows impaired ACL‐agonist muscle (i.e. hamstring) activity during sidecutting in response to acute fatigue induced by handball match play. Thus, screening procedures should involve functional movements to reveal specific fatigue‐induced deficits in ACL‐agonist muscle activation during high‐risk phases of match play.

Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: an EMG study with rehabilitation implications.

Background The medial hamstring muscle has the potential to prevent excessive dynamic valgus and external rotation of the knee joint during sports. Thus, specific training targeting the medial hamstring muscle seems important to avoid knee injuries. Objective The aim was to investigate the medial and lateral hamstring muscle activation balance during 14 selected therapeutic exercises. Study design The study design involved single-occasion repeated measures in a randomised manner. Sixteen female elite handball and soccer players with a mean (SD) age of 23 (3) years and no previous history of knee injury participated in the present study. Electromyographic (EMG) activity of the lateral (biceps femoris – BF) and medial (semitendinosus – ST) hamstring muscle was measured during selected strengthening and balance/coordination exercises, and normalised to EMG during isometric maximal voluntary contraction (MVC). A two-way analysis of variance was performed using the mixed procedure to determine whether differences existed in normalised EMG between exercises and muscles. Results Kettlebell swing and Romanian deadlift targeted specifically ST over BF (Δ17–22%, p<0.05) at very high levels of normalised EMG (73–115% of MVC). In contrast, the supine leg curl and hip extension specifically targeted the BF over the ST (Δ 20–23%, p<0.05) at very high levels of normalised EMG (75–87% of MVC). Conclusion Specific therapeutic exercises targeting the hamstrings can be divided into ST dominant or BF dominant hamstring exercises. Due to distinct functions of the medial and lateral hamstring muscles, this is an important knowledge in respect to prophylactic training and physical therapist practice.

Nonoperative dynamic treatment of acute achilles tendon rupture: the influence of early weight-bearing on clinical outcome: a blinded, randomized controlled trial.

BACKGROUND Dynamic rehabilitation has been suggested to be an important part of nonoperative treatment of acute Achilles tendon rupture that results in functional outcome and rerupture rates comparable with those of operative treatment. However, the optimal role of weight-bearing during early rehabilitation remains unclear. The purpose of this study was to compare immediate weight-bearing with non-weight-bearing in a nonoperative dynamic treatment protocol for Achilles tendon rupture. METHODS The study was conducted as a blinded, randomized, controlled, parallel superiority trial. Patients eighteen to sixty years of age were eligible for inclusion. Both groups were treated nonoperatively with controlled early motion. The intervention group was allowed full weight-bearing from day one, and the control group was non-weight-bearing for six weeks. The primary outcome was the Achilles tendon Total Rupture Score (ATRS) after one year. Secondary outcomes included heel-rise work, health-related quality of life, and the rerupture rate. Outcome assessors were blinded to the intervention. RESULTS Thirty patients were randomized to each group; twenty-nine in the weight-bearing group and twenty-seven in the control group were analyzed. The only significant difference between the groups was better health-related quality of life in the weight-bearing group at twelve months (p = 0.009). The mean ATRS at twelve months was 73 in the weight-bearing group and 74 in the control group (p = 0.81). At twelve months, the total heel-rise work performed by the injured limb relative to that by the uninjured limb was 53% in the weight-bearing group and 58% in the control group (p = 0.37). There were three reruptures in the weight-bearing group and two in the control group (p = 1.0). CONCLUSIONS The ATRS and heel-rise work results did not differ significantly between the groups. The rerupture rate was 9% overall, and both groups had substantial functional deficits in the injured limb compared with the uninjured limb. Immediate weight-bearing can be recommended as an option in the nonoperative treatment of Achilles tendon rupture.