Strength Measurements in Acute Hamstring Injuries: Intertester Reliability and Prognostic Value of Handheld Dynamometry

Study Design Cohort study, repeated measures. Background Although hamstring strength measurements are used for assessing prognosis and monitoring recovery after hamstring injury, their actual clinical relevance has not been established. Handheld dynamometry (HHD) is a commonly used method of measuring muscle strength. The reliability of HHD has not been determined in athletes with acute hamstring injuries. Objectives To determine the intertester reliability and the prognostic value of hamstring HHD strength measurement in acute hamstring injuries. Methods We measured knee flexion strength with HHD in 75 athletes at 2 visits, at baseline (within 5 days of hamstring injury) and follow-up (5 to 7 days after the baseline measurement). We assessed isometric hamstring strength in 15° and 90° of knee flexion. Reliability analysis testing was performed by 2 testers independently at the follow-up visit. We recorded the time needed to return to play (RTP) up to 6 months following baseline. Results The intraclass correlation coefficients of the strength measurements in injured hamstrings were between 0.75 and 0.83. There was a statistically significant but weak correlation between the time to RTP and the strength deficit at 15° of knee flexion measured at baseline (Spearman r = 0.25, P = .045) and at the follow-up visit (Spearman r = 0.26, P = .034). Up to 7% of the variance in time to RTP is explained by this strength deficit. None of the other strength variables were significantly correlated with time to RTP. Conclusion Hamstring strength can be reliably measured with HHD in athletes with acute hamstring injuries. The prognostic value of strength measurements is limited, as there is only a weak association between the time to RTP and hamstring strength deficit after acute injury. Level of Evidence Prognosis, level 4. J Orthop Sports Phys Ther 2016;46(8):689-696. Epub 12 May 2016. doi:10.2519/jospt.2016.636

Swarm Observations of Dawn/Dusk Asymmetries Between Pedersen Conductance in Upward and Downward Field-Aligned Current Regions

The locations of region 1 and 2 field-aligned current systems were determined using fluxgate magnetometer measurements from 875 dawn-dusk passes of the Swarm A satellite. Within each field-aligned current region, the ionospheric Pedersen conductance was derived from the newly corrected Swarm electric and magnetic field measurements. The Pedersen conductances are generally consistent with photoionization models. However, we show that the in situ method of determining Pedersen conductance allows for a more complete description of magnetosphere-ionosphere coupling and should be used in future studies when possible. We show that, overall, the Pedersen conductance is larger in the upward current region than in the downward region by ∼0.6 S on the dawn side of the Earth. Meanwhile, the dusk side Pedersen conductance is equivalent in both current regions. We attribute this asymmetry to dawn side energetic electron precipitation, commonly associated with substorm electron injections from the magnetotail