Purpose: This study assessed differences in measures of the muscle tendon unit between infants born preterm and infants born full-term.
Methods: Twenty infants born between 26 and 36 weeks of gestation comprised the preterm group and 21 infants born between 38 and 42 weeks of gestation comprised the full-term group. Gastrocnemius-soleus measurements were obtained with a taut tendon and relaxed muscle belly (Ao), and with a taut tendon and elongated muscle belly (Amax). Muscle extensibility measurements were obtained with a goniometer. Ao to Amax was the difference between Ao and Amax measurements.
Results: Statistically significant differences were found for both measures of muscle extensibility, but not for the difference between these measures. The preterm group demonstrated measures of Ao and Amax in more extended ankle positions.
Conclusion: Muscle length differences are present between infants born full-term and infants born preterm. These differences are most likely due to differences in tendon length.