Patellar Tendon Stiffness Is Not Reduced During Pregnancy.

Marie Elena Bey,Larry Hinkson,Robert Marzilger,Adamantios Arampatzis,Kirsten Legerlotz

doi:10.3389/fphys.2019.00334

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.

Highlights

It is well established that physical activity during pregnancy has beneficial effects on maternal and fetal health (Vladutiu et al, 2010) decreasing the risk of pregnancy associated disorders such as preeclampsia or gestational diabetes (DeMaio and Magann, 2009)
Even when moderate exercise is undertaken, pregnant women are often cautioned that hormonal changes during pregnancy may increase ligament and tendon compliance (Östgaard et al, 1993; Dumas and Reid, 1997; Ritchie, 2003) possibly leading to connective tissue injuries and joint pain, such as patellofemoral dysfunction (Ritchie, 2003; Harland et al, 2014)
In the pregnant women patellar tendon properties and the maximum knee joint moment were determined in the early stage of pregnancy [EP, 16 ± 4 week of pregnancy (WoP)], the late stage of pregnancy (LP, 29 ± 4 WoP) and at least 6 months postpartum (PP, 32 ± 9 weeks)

Summary

INTRODUCTION

It is well established that physical activity during pregnancy has beneficial effects on maternal and fetal health (Vladutiu et al, 2010) decreasing the risk of pregnancy associated disorders such as preeclampsia or gestational diabetes (DeMaio and Magann, 2009). Since impairments in postural stability are associated with the high incidence of falls in pregnant women (Dunning et al, 2010) this may, in turn, lead to further injuries It has been known for decades and has been well documented that the compliance of the pubic ligaments increases during pregnancy which is an essential process to facilitate childbirth (Young, 1940). Our study may contribute to a better understanding of hormonal effects on female connective tissue properties in general, as in other contexts hormonal variations are discussed to affect injury risk (e.g., association of anterior cruciate ligament rupture incidence with certain phases of the menstrual cycle) (Herzberg et al, 2017)

Participants

Experimental Setup

RESULTS

DISCUSSION