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Muscle size is an important determinant of muscular fitness and health, and so it is important to have accurate estimates of actual muscle growth in children. This study compared actual versus age‐predicted growth rates of the medial gastrocnemius (MG) muscle in young children over a 12‐month period. Three‐dimensional ultrasound was used to measure MG length and volume in 50 children (mean ± standard deviation [SD] age = 70.3 ± 29.9 months) to establish age‐predicted muscle growth rates using a least‐squares linear regression. Twenty children (mean ± SD age = 78.5 ± 27.2 months) were followed up at 6 and 12 months to establish actual muscle growth of MG volume and length. These data were then compared to their age‐predicted muscle growth from the linear regression equation using paired t‐tests and Bland–Altman limits of agreement method. Age‐predicted MG growth significantly underestimated actual muscle growth for both volume and length at each timepoint. On average, actual muscle volume and length were 11.5% and 21.5% greater than the age‐predicted volume and length respectively. Caution is warranted when predicting future muscle size in young children based solely on age. [ABSTRACT FROM AUTHOR]

Wind energy generation has become an important means to reduce reliance on fossil fuels and mitigate against human‐induced climate change, but could also represent a significant human–wildlife conflict. Airborne taxa such as birds may be particularly sensitive to collision mortality with wind turbines, yet the relative vulnerability of species' populations across their annual life cycles has not been evaluated.Using GPS telemetry, we studied the movements of lesser black‐backed gulls Larus fuscus from three UK breeding colonies through their annual cycle. We modelled the distance travelled by birds at altitudes between the minimum and maximum rotor sweep zone of turbines, combined with the probability of collision, to estimate sensitivity to collision. Sensitivity was then combined with turbine density (exposure) to evaluate spatio‐temporal vulnerability.Sensitivity was highest near to colonies during the breeding season, where a greater distance travelled by birds was in concentrated areas where they were exposed to turbines.Consequently, vulnerability was high near to colonies but was also high at some migration bottlenecks and wintering sites where, despite a reduced sensitivity, exposure to turbines was greatest.Synthesis and applications. Our framework combines bird‐borne telemetry and spatial data on the location of wind turbines to identify potential areas of conflict for migratory populations throughout their annual cycle. This approach can aid the wind farm planning process by: (a) providing sensitivity maps to inform wind farm placement, helping minimize impacts; (b) identifying areas of high vulnerability where mitigation warrants exploration; (c) highlighting potential cumulative impacts of developments over international boundaries and (d) informing the conservation status of species at protected sites. Our methods can identify pressures and linkages for populations using effect‐specific metrics that are transferable and could help resolve other human–wildlife conflicts. [ABSTRACT FROM AUTHOR]

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Aim This study investigates the in vivo function of the medial gastrocnemius and soleus muscle-tendon units ( MTU), fascicles, and tendons during walking in children with cerebral palsy ( CP) and an equinus gait pattern. Method Fourteen children with CP (9 males, 5 females; mean age 10y 6mo, standard deviation [ SD] 2y 11mo; GMFCS level I=8, II=6), and 10 typically developing (6 males, 4 females; mean age 10y, SD 2y 1mo) undertook full body 3D gait analysis and simultaneous B-mode ultrasound images of the medial gastrocnemius and soleus fascicles during level walking. Fascicle lengths were analysed using a semi-automated tracking algorithm and MTUs using OpenSim. Statistical parametric mapping (two-sample t-test) was used to compare differences between groups ( p<0.05). Results In the CP group medial gastrocnemius fascicles lengthened during mid-stance gait and remained longer into late-stance compared to the typically developing group ( p<0.001). CP medial gastrocnemius fascicles shortened less during stance (1.16mm [ SD 1.47mm]) compared to the typically developing group (4.48mm [ SD 1.94mm], p<0.001). In the CP group the medial gastrocnemius and soleus MTU and tendon were longer during early- and mid-stance ( p<0.001). Ankle power during push-off ( p=0.015) and positive work ( p<0.002) and net work ( p<0.001) were significantly lower in the CP group. Interpretation Eccentric action of the CP medial gastrocnemius muscle fascicles during mid-stance walking is consistent with reduced volume and neuromuscular control of impaired muscle. Reduced ankle push-off power and positive work in the children with CP may be attributed to reduced active medial gastrocnemius fascicle shortening. These findings suggest a reliance on passive force generation for forward propulsion during equinus gait. [ABSTRACT FROM AUTHOR]

Aim: Calf muscle growth in children with unilateral cerebral palsy (UCP) and bilateral cerebral palsy (BCP) is unknown. This cross-sectional study examines the medial gastrocnemius growth rates of ambulatory children with UCP and BCP compared with children with typical development (CTD), aged 2 to 9 years.Method: Fifty children with UCP (mean age 66mo [SD 18], 29 males, Gross Motor Function Classification System [GMFCS] I=32, II=18), 50 children with BCP (age 64mo [SD 19], 31 males, GMFCS I=21, II=29), and 78 CTD (age 64mo [SD 16], 40 males) participated in the study. The medial gastrocnemius muscle volume was measured at rest using a validated freehand three-dimensional (3D) ultrasound method.Results: Normalized medial gastrocnemius muscle growth rate was significantly less in the children with UCP (0.001 mL/kg/mo) compared with the BCP (0.015 mL/kg/mo, p=0.001) and CTD (0.014 mL/kg/mo, p<0.001) groups. Normalized medial gastrocnemius muscle growth rate was the same in the BCP and CTD groups (p=0.77).Interpretation: The normalized growth rate of the medial gastrocnemius muscle in children aged 2 to 9 years with UCP is significantly lower compared with children with BCP and CTD. The growth rate differences in the children with UCP compared with BCP raises questions about the underlying mechanisms that lead to reduced growth in each cerebral palsy (CP) group and potential differences in muscle recovery response in UCP and BCP following treatment. [ABSTRACT FROM AUTHOR]

The aim of this article was to compare medial gastrocnemius muscle volume, physiological cross-sectional area (PCSA), muscle length, fascicle length, and pennation angle in children aged 2 to 5 years with spastic cerebral palsy (CP) and in typically developing children. Fifteen children with spastic CP (11 males, four females; mean age 45mo [SD 15mo]; five with hemiplega; 10 with diplega; 10 classified at Gross Motor Function Classification System (GMFCS) level I, five at GMFCS level II) and 20 typically developing children (11 males, nine females; mean age 48mo [SD 14mo]) participated in the study. Individuals with spastic CP were included if they had a minimum range of motion of 0° ankle dorsiflexion with the knee extended and were excluded if they had had previous botulinum toxin treatment to the calf muscles or previous calf surgery. Typically developing children were included if they were able to walk independently and were excluded if there was a history of previous lower leg injury or other developmental disorder affecting the lower limb. Freehand two-dimensional and three-dimensional ultrasound was used to assess muscle properties of the relaxed medial gastrocnemius muscle at three ankle joint angles: maximum dorsiflexion, neutral and maximum plantarflexion. PCSA was calculated as a function of muscle volume and muscle fascicle length and pennation angle was recorded at the neutral ankle joint angle. Medial gastrocnemius muscle volume was 22% lower in the group with spastic CP than in the typically developing group, which in the absence of significant group differences in neutral fascicle length gave rise to an equivalent reduction in PCSA for the group with spastic CP. Significant positive correlations were found between muscle volume and age ( r=0.63-0.65) and between muscle length and age ( r=0.72-0.81) in both groups. Maximum ankle dorsiflexion angle was also reduced in the group with spastic CP (8°) compared with the typically developing group (26°). The observed reduction in muscle PCSA in the group with spastic CP would be expected to contribute to the clinically observed muscle weakness in spastic CP and suggests the need for early intervention in order to minimize loss of muscle PCSA in spastic CP. [ABSTRACT FROM AUTHOR]

Fixed shortening of a muscle, or contracture, often develops in individuals with an upper motor neuron disorder. A clinical measure of muscle length would therefore be useful for identifying the presence of muscle contracture, tracking changes over time and evaluating the effect of interventions. This study compared a novel ultrasound-tape length method with a previously validated freehand 3D ultrasound method for measuring muscle length. The ultrasound-tape method intra-session reliability was also assessed. Resting medial gastrocnemius muscle length was measured at three ankle joint angles in 15 typically developed (TD) adults and nine adults with cerebral palsy (CP) using the two methods. The ultrasound-tape method on average overestimated the muscle length in the TD group by < 0.1% (95% CI, 6%) and underestimated in the muscle length in the CP group by 0.1% (95% CI, 6%) compared with the 3D ultrasound method. Intra-session reliability of the ultrasound-tape method was high, with intra-class correlation coefficients > 0.99. The ultrasound-tape method has sufficient accuracy to detect clinically relevant differences and changes in medial gastrocnemius muscle length and may therefore be a useful clinical tool for assessing muscle length changes associated with contracture. [ABSTRACT FROM AUTHOR]

This commentary is on the original article by Herskind et al. on pages 485–491 of this issue. [ABSTRACT FROM AUTHOR]

This commentary is on the original article by Smith et al on pages 264–270 of this issue. [ABSTRACT FROM AUTHOR]