Effect of gender and learning on the relationship between muscle architecture and strength expression
Blazevich, AJ & Zhou, S 2003, 'Effect of gender and learning on the relationship between muscle architecture and strength expression', paper presented to 7th International Olympics Committee World Congress of Sport Sciences, Athens, Greece. 10 October.
Among other muscular factors, a muscle’s size and architecture are considered important determinants of its contractile properties. Despite this, the influence of muscle architecture on force development has not been precisely established. This could be somewhat quantified by examining the relationship between muscle architecture and force production in unfamiliar, single-joint strength tests, where learning affects contribute little to strength expression. Furthermore, it is unclear whether the muscle architecture-force relationship is the same in men as it is for women. The present study examined the relationship between quadriceps muscle strength and vastus lateralis muscle (VL) architecture in men and women unfamiliar with strength training. The effect of task learning was determined by re-measuring a subset of the subjects after test practice.
Ultrasound scans (B-mode, 7.5 MHz linear transducer) of the VL muscles of 14 men and 15 women unaccustomed to resistance exercise were taken at distal, middle and proximal sites over the muscle. From them, anatomical (AMT) and physiological muscle thickness (PMT), fascicle angle (FA) and fascicle length (FL) were measured after points on echoes of the aponeurosis and fascicles were identified and digitized using Peak Motion Analysis software (Peak Performance Technologies, USA). Subjects also performed maximal isokinetic knee extension tests at 1.05 (concentric and eccentric) and 3.14 rad.s-1 (concentric only) with a hip angle of 1.57 rad. 7 men and 8 women subsequently performed 10 training sessions (3 per week) involving 4 sets of 6 maximal, isokinetic, concentric/eccentric knee extensions at 1.05 rad.s-1, after which knee extension strength and muscle size and architecture of the VL were re-tested.
Men produced significantly more torque than women at both 1.05 (concentric: men 215.2±62.0, women 151.1±28.3 Nm; eccentric: men 277.2±77.1, women 195.3±39.4 Nm) and 3.14 rad.s-1 (men 145.4±36.0, women 105.0±19.9 Nm). There were however no significant differences in muscle size (PMT or AMT) or architecture between genders. In women, there were significant correlations (0.640.70, p<0.05-0.001) between concentric torque at 1.05 rad.s-1 and both AMT and PMT at proximal and middle muscle sites, but there were no relationships between FA or FL and strength. In men, there were significant positive correlations (0.610.78, p<0.05-0.01) between FL at the distal site and strength in the tests, but no other relationships. When the most and least strong women in each test were statistically compared, no differences in muscle architecture existed between the groups, although the strongest women in the eccentric test had a greater AMT at mid-thigh (F=5.2, p<0.05). There were also no differences for the most and least strong men, except for the strongest men in the eccentric test who had a greater FA at mid-thigh (F=7.6, p<0.05).
In the training subset, there were no changes in muscle size or architecture after the training despite significant (p<0.05) increases in torque production in all three tests. There were few significant correlations between strength and muscle size and architecture in men or women before training. After training eccentric strength at 1.05 rad.s-1 and concentric strength at 1.05 rad.s-1 were significantly correlated with both AMT and PMT at proximal and mid-thigh sites in women. In men, eccentric torque and torque at 3.14 rad.s-1 were significantly correlated with AMT and PMT at mid-thigh (0.830.90, p<0.05) and FL at mid-thigh (-0.86-0.88, p<0.05).
Since there were no differences between men and women in VL muscle size or architecture, gender-related strength differences must be accounted for by other factors such as differences in specific tension, muscle recruitment strategies or patella tendon moment arms. In men, the poor correlation between strength and muscle architecture and lack of difference between most and least strong subjects suggests that other factors contribute more to strength expression. In women, there was some relationship between muscle size and strength in the slow concentric knee extension test, but the lack of relationships between architecture and torque in other tests, and lack of difference in muscle size and architecture between the most and least strong women, indicates that factors other than muscle size and architecture might be at least as important. There were no changes in muscle size or architecture after training, despite there being significant strength increases in both men and women. Subjects with greater AMT or PMT (men and women), or shorter fascicle lengths (men) tended to be stronger after the training. It is likely therefore that muscle size and architecture make a greater contribution to strength expression after learning.