An electromyographic exploratory study comparing the difference in the onset of hamstring and quadriceps contraction in patients with anterior knee pain.

Idiopathic anterior knee pain in teenagers and young adults is a common condition. Patellar maltracking has been considered as a causative factor. The aim of our study was to investigate whether there was a difference in the timing of electromyographic (EMG) activity in the medial and lateral hamstring and quadriceps muscles of patients with anterior knee pain compared to asymptomatic control participants. This was a cross sectional observational study measuring EMG activation patterns. Two groups of participants were tested, one patient (mean age 15 years, n = 20) and one asymptomatic control (mean age 16 years, n = 17). Surface EMG (sampling rate 1000 Hz) was recorded from vastus medialis obliqus, vastus lateralis, and the medial and lateral hamstrings during three repetitions of maximal voluntary isometric contractions. The relative timing of the medial and lateral quadriceps and hamstrings was evaluated. The mean (95% confidence interval) difference between the groups in the lateral-medial hamstring onset timing was 53.8(1.9 to 105.6)ms during the maximal contraction. An independent t test showed that this difference was statistically significant (p = 0.043). The differences between the groups in the relative VMO to VL onset did not reach statistical significance. The results of this study suggest that the lateral hamstrings contract significantly earlier in patients with AKP compared to healthy controls for this small cohort. This altered activation pattern could produce external rotation of the tibia on the femur and cause lateral patella tracking.

Hamstring length in patellofemoral pain syndrome.

OBJECTIVES: To investigate whether there was a difference in hamstring length between patients with patellofemoral pain syndrome and healthy asymptomatic controls aged 18 to 35 years. DESIGN: A cross-sectional observational study measuring hamstring length in patients and asymptomatic controls. SETTING: Hospital physiotherapy department. PARTICIPANTS: Two groups were tested; one group diagnosed with patellofemoral pain syndrome (mean age 27 years, n=11, six males, five females) and one group of asymptomatic controls (mean age 25 years, n=25, 13 males, 12 females). MAIN OUTCOME MEASURES: Hamstring length was evaluated using the passive knee extension method to measure popliteal angle. RESULTS: The mean (standard deviation) values for hamstring length were 145.6 (8.7) degrees for patients with patellofemoral pain syndrome and 153.7 (10.1) degrees for the asymptomatic controls. The mean (95% confidence interval) difference between the groups was 8.0 (0.8 to 15.1) degrees , and analysis with a t-test revealed that this was statistically significant (P<0.05). CONCLUSIONS: This study found that patients with patellofemoral pain had shorter hamstring muscles than asymptomatic controls. It is not clear whether this is a cause or effect of the condition. Further research is suggested to study how hamstring length changes with rehabilitation, and the relationship with pain.

Prevalence of asthma and chronic respiratory symptoms among Alaska Native children.

STUDY OBJECTIVES: To quantify the prevalence and impact of chronic respiratory symptoms among predominantly Alaska Native (AN)/American Indian (AI) middle school students. DESIGN: School-based prevalence assessment using the International Study of Asthma and Allergy in Children survey, with supplemental video material and added questions about productive cough, exposure to tobacco smoke, and the functional impact of symptoms. SETTING: The Yukon-Kuskokwim delta region of western Alaska. PARTICIPANTS: A total of 466 children in the sixth to ninth grades, 81% of whom are AN/AI (377 children). INTERVENTIONS: No study intervention. RESULTS: Among the 377 AN/AI children, 40% reported one of the following three categories of chronic respiratory disease: physician-diagnosed asthma, 7.4%; asthma-like symptoms (ALS) without an asthma diagnosis, 11.4%; and chronic productive cough (CPC) without asthma diagnosis or symptoms, 21.5%. Symptom prevalence differed substantially between the largest town in the region and rural villages. After an adjustment for demographic factors, exposure to environmental tobacco smoke, active tobacco smoking, and self-report of atopy, village residents were 63% less likely to have ALS (p = 0.009), and had a twofold greater risk of CPC (p < 0.001) compared to children living in the town. Children with respiratory symptoms experienced sleep disturbances and accessed clinic visits for respiratory problems more often than did asymptomatic children. CONCLUSIONS: Chronic respiratory symptoms are very common among AN children. CPC is an important nonasthmatic respiratory condition in this population. The differing patterns of respiratory illness within this region may help to elucidate the specific risk factors for asthma and chronic bronchitis in children.