# Lower Limb Joint Coordination and Coordination Variability During Landing: A Scoping Review
## 3 Results
### Age Differences: Children Versus Adults  
Age and development level introduce another dimension to landing coordination. Young children, adolescents, and adults differ in musculoskeletal maturity, motor control experience, and strength--all factors that can shape how joints coordinate during a landing. Several studies compared children to adults (or examined children of different ages) to understand how coordination patterns and variability evolve with development. **Coordination Variability in Children:** Research indicates that children exhibit higher coordination variability than adults during complex motor tasks, reflecting a learning process and less stable neuromuscular control. [PERSON], [PERSON] [10] investigated counter-movement jump landings in children versus adults and found that intra-subject coordination variability was higher in children, especially for couplings of proximal segments. Practically, on each landing attempt, a given child showed more fluctuation in how their hip and knee moved relative to each other (or how the thigh and shank segments were coordinated) compared to an adult performing the same task. Children also showed less consistency in the specific coordination pattern they \"chose\", implying they were still exploring different movement solutions rather than having a well-ingrained strategy. Adults, in contrast, tended to exhibit a repeatable coordination pattern for countermovement landings, indicative of a more refined and stable motor solution developed through practice and neuromuscular maturation. A recent study by [PERSON], [PERSON] [25] specifically looked at single-leg drop landings in children who practice sports (gymnastics or volleyball) versus non-sporting children. They found that coordination patterns during the landing's impact phase differed by group: for example, in the frontal plane, non-athletic children more frequently displayed an anti-phase with proximal dominance pattern (meaning the hip and knee were moving in opposite directions or out of sync, with the hip movement dominating) compared to sport-trained children. Moreover, they noted differences in variability: during certain phases of landing (like the second peak of ground reaction force), children in different sports groups had different variability levels (in this case. volleyball players showed higher coordination variability than gymnasts in one phase). This could relate to the nature of their training; volleyball involves varied jump-landing scenarios (potentially encouraging adaptability), whereas gymnastics often emphasizes sticking landings (perhaps encouraging a consistent strategy). Another key observation was that the control (non-athlete) children had a greater frequency of less coordinated patterns (like the anti-phase mentioned) than the athletic children, underscoring how practice and skill development in youth can refine coordination. **Movement Strategies among Children versus Adults:** Beyond variability, the absolute coordination patterns can differ with age. Young children, especially those under \(\sim\)10 years old, tend to land \"stiffer\"--characterized by less hip and knee flexion and shorter landing phases. This can correlate with a coordination pattern that is not optimized for absorbing force (i.e., more in-phase ankle-knee motion meaning both joints lock up somewhat). As children get older and stronger, they generally increase their knee and hip flexion usage during landing, which is accompanied by a shift in coordination: more pronounced in-phase hip-knee flexion (both joints flex together smoothly) and better timing with the ankle. Essentially, older children and adults show a coordinated flexion strategy (often called a soft-landing technique) where joints flex in harmony to decelerate the body. Younger children often have not mastered that, resulting in either asynchrony (one joint moving too much relative to another) or highly variable patterns from trial to trial.