Muscle Damage following Maximal Eccentric Knee Extensions in Males and Females

Abstract

Aim: To investigate whether there is a sex difference in exercise induced muscle damage.

Materials and method: Vastus Lateralis and patella tendon properties were measured in males and females using ultrasonography. During maximal voluntary eccentric knee extensions (12 reps x 6 sets), Vastus Lateralis fascicle lengthening and maximal voluntary eccentric knee extensions torque were recorded every 10° of knee joint angle (20-90°). Isometric torque, Creatine Kinase and muscle soreness were measured pre, post, 48, 96 and 168 hours post damage as markers of exercise induced muscle damage.

Results: Patella tendon stiffness and Vastus Lateralis fascicle lengthening were significantly higher in males compared to females (p<0.05). There was no sex difference in isometric torque loss and muscle soreness post exercise induced muscle damage (p>0.05). Creatine Kinase levels post exercise induced muscle damage were higher in males compared to females (p<0.05), and remained higher when maximal voluntary eccentric knee extension torque, relative to estimated quadriceps anatomical cross sectional area, was taken as a covariate (p<0.05).

Conclusion: Based on isometric torque loss, there is no sex difference in exercise induced muscle damage. The higher Creatine Kinase in males could not be explained by differences in maximal voluntary eccentric knee extension torque, Vastus Lateralis fascicle lengthening and patella tendon stiffness. Further research is required to understand the significant sex differences in Creatine Kinase levels following exercise induced muscle damage.

Fig 1

a) Example figure of measuring patella tendon cross-sectional area at 50% of patella tendon length using ultrasound. b) Example figure of measuring patella tendon lengthening using ultrasound. The red line emphasizes the shadow cast by the echo-absorptive marker on the skin, with the displacement of the proximal or distal anatomical marker made relative to this line. The distal insertion of the patella tendon into the tibia is shown in (b).

Fig 2. Maximal voluntary isometric knee extension torque loss, one, 48, 96 and 168 hours post exercise induced muscle damage (EIMD) in males and females.

Maximal voluntary isometric knee extension torque loss is expressed as a percentage of maximal voluntary isometric knee extension torque pre exercise induced muscle damage. Data is presented as means ± SD. Significant difference from Pre–damage * p <0.05, ** p < 0.01.

Fig 3

a) Serum creatine kinase levels, pre (-48 hours) exercise induced muscle damage (EIMD) and 1, 48, 96 and 168 hours post EIMD in males and females. b) Serum creatine kinase levels made relative to Vastus Lateralis anatomical cross-sectional area (VL_ACSA), pre (-48 hours) exercise induced muscle damage (EIMD) and 1, 48, 96 and 168 hours post EIMD in males and females. Data is presented as means ± SD. * Males serum creatine kinase levels significantly higher than females p<0.05, ** Males serum creatine kinase levels significantly higher than females p<0.01.