Patellar Tendon Stiffness Is Not Reduced During Pregnancy

Abstract

It is believed that hormonal changes during pregnancy lead to an increased compliance in ligaments and tendons, increasing the risk to suffer from connective tissue injuries particularly during exercise. While the laxity of the pelvic ligaments may increase to facilitate childbirth, to our knowledge no study has ever investigated the mechanical properties of human tendons in different stages of pregnancy. Thus, the purpose of our longitudinal study was to investigate the mechanical properties of the patellar tendon in different stages of pregnancy and postpartum. Nineteen pregnant women (30 ± 4 years) and 11 non-pregnant controls (28 ± 3 years) performed maximum isometric knee extension contractions on a dynamometer. Muscle strength and mechanical properties of the patellar tendon were determined integrating ultrasound, kinematic, and electromyographic measurements. In pregnant women, measurements were performed in the 16 ± 4th week of pregnancy (EP), the 29 ± 4th week of pregnancy (LP) and 32 ± 9th weeks postpartum (PP). On average, muscle strength as well as patellar tendon stiffness, force, and relative strain did not change during pregnancy and did not differ from non-pregnant controls. Tendon length measured at 90° knee flexion continuously increased during and after pregnancy (tendon length PP>EP; PP>controls). Our results indicate that patellar tendon stiffness is not universally affected by pregnancy. We found no evidence to support the often stated assumption that tendons would become more compliant during pregnancy. However, variability between individuals as well as the progressive increase in tendon rest length during and after pregnancy and its implications on injury risk need to be further examined.

The effect of a maternity support belt on static stability and posture in pregnant and non-pregnant women

“…The postpartum values were also compared with values from a non-pregnant control group. We hypothesized that patellar tendon stifness decreases during pregnancy (Bey et al, 2019a).…”

“…For the non-pregnant group, the same data were collected as for the pregnant group, while the measurements in the non-pregnant group were conducted once. Within this research project further data such as tendon properties were obtained and published as separate article (Bey et al, 2019a).…”

“…The knee fexor moment was assessed by EMG based estimates of the knee fexors' co-activation (Mademli et al, 2004). Details of the correction procedures have been described in previous studies (Arampatzis et al, 2004;Mademli et al, 2004;Bey et al, 2019a).…”

Vastus Lateralis Architecture Changes During Pregnancy – A Longitudinal Study

“…Within this research project further data such as tendon properties were obtained and published as separate article (Bey et al, 2019).…”

“…The knee flexor moment was assessed by electromyographic based estimates of the knee flexors’ co-activation (Mademli et al, 2004). Details of the correction procedures have been described in previous studies (Arampatzis et al, 2004; Mademli et al, 2004; Bey et al, 2019).…”