What Are Calves?
The calf, the thick portion of the human lower leg posterior to the knee and anterior to the ankle, mainly consists of two primary muscles: the gastrocnemius and the soleus. The gastrocnemius is the more massively developed of the muscles, the peak or ‘bump’ associated with it forming the calf bulge, and the soleus is a relatively flat inverted V-shaped structure settled under the gastrocnemius [1].
What Is The Role of Calves?
The calf muscles are involved in several movements and locomotor stability tasks, including walking, running, and jumping. When moving against gravity (consider the second half of a single-limb stance phase of gait, for instance), the calf muscles resist the force of gravity rather than propelling the body any further [2].
When you’re running, you activate these muscles each time your foot pushes off, bringing your leg forward. They also work to propel you with each push-off and landing as they extend your foot and allow it to then flex as your foot strikes and pushes off again. They also help to soften the shock of impact when you land, aid you in maintaining your balance, and improve your ankle flexibility [3].
The calf muscles also function in static balance, so if the calf muscles are missing or not working, there is an immediate compensatory response for static balance (rather than speed) [2].
Do Women or Men Have Better Calves?
Whether women or men have ‘better’ calves is open to individual interpretation, and ‘better’ ultimately depends on one’s criteria for comparison. However, scientific studies have revealed differences in the calves possessed by males versus females.
One study found that calf circumference positively correlates with calf muscle thickness for both men and women: the bigger your calf circumference, the bigger your muscle thickness [4]. Two other studies have noted that, on average, females tend to have longer muscle fibre bundle lengths, while males have thicker muscles and more considerable angles of pennation [5].
Regarding physical performance, one study determined that women showed poorer leg stiffness with hopping exercises than men. When this was corrected for body mass, gender differences in leg stiffness were eliminated [6]. Another study examined the relationship between intramyocellular lipid content of the tibialis anterior muscle and physical performance in men, which showed that the former was negatively associated with the latter. For women, the intramyocellular lipid content of the soleus muscle was negatively associated with physical performance [7].
Regarding force production, a single study reported that males between 16 and 22 years of age had greater strength for both knee flexors (hamstrings) and hip (hip flexors) as well as total leg strength than females [8]. Another study reported that women are more quadriceps dominant than males when performing single-leg squats, while men are more hamstrings dominant [9].
What Promotes the Development of Calf Muscle?
Like other skeletal muscles, the development of calf muscle is a complex process influenced by various factors.
A key factor for muscle differentiation is controlling Wnt/beta-catenin stem cell regulation of mesenchymal stem cell (MSC) differentiation and myogenesis (muscle cell development) versus adipogenesis (fat cell development). This is modulated through the upregulation of Wnt/beta-catenin and the downregulation of Wnt/beta-catenin, respectively [10].
In addition, Arachidonic acid (AA) and its major prostaglandin derivatives also increase muscle size by stimulating the proliferation of myogenic cells. For instance, 13 to 24% more cells proliferate following an 8-day treatment with an AA/PGH2 agonist [11].
The specific genes Atp2a1, Tmod4, Lmod3, Ryr1, and Mybpc2 all play a role in glycolysis/gluconeogenesis, the AMPK pathway, the insulin pathway, mTOR signalling, PI3K/AKT, muscle formation. They are part of extracellular matrix receptor interaction, etc. – all very important in muscle hypertrophy [12].
The timings of differentiation are also critical; for example, overexpression of Sonic Hedgehog (Shh) induces overexpression of Bmp-2 and Bmp-7, thus delaying the onset of muscle differentiation, enlarging the population of myogenic progenitor cells and leading to hyperplasia of the muscle [13].
Vitamin A administration to neonatal calves has been shown to enhance postnatal muscle growth by promoting myogenesis and increasing satellite cell density [14].
In this context, lnc000100, a long non-coding RNA (lncRNA), was demonstrated to be a direct regulator of myogenesis; knocking down lnc000100 inhibited cell proliferation but promoted cell differentiation [15].
Lastly, Vitamin K2 has been shown to improve the proliferation and migration of bovine skeletal muscle cells in vitro [16].
Are Calves Genetic?
Like other physical characteristics, the size and shape of your calves are influenced by a combination of your genetics and your environment. Though none of the studies below speak directly to human calf genetics, each is founded on research concerning how genetics can influence animal physical traits, some of which can be broadly applied to humans.
Genetics are also responsible for the presence of body parts and the size and shape of those parts in animals of all kinds; for example, body measurements (or weights) in cattle are strongly affected by genetic predispositions. Looking at Japanese Black calves over a year (0-12 months), a study found maternal heritabilities (genetic markers inherited from mother to calf) of 0.08 at 0 months and 0.33 at 4 months of age, respectively [17].
Another recent study conducted a genome-wide association screen to show that SNP markers associated with beef heifer reproduction traits and beef calf performance traits were located on multiple chromosomes, which suggests that more than one gene may underlie these traits [18].
Although genetics put limits on the range of possibilities, they don’t absolutely dictate what does or doesn’t happen. Environmental forces, such as diet and physical activity, significantly impact your muscle mass and body composition. This includes calf size, for example.
To sum up, calves are primarily influenced by your genes, which gives you the dimension of your lower-leg musculus - but since your environment since the time of birth crucially affects the expression of genes, you can, despite the genetic program, steer the dimensions and appearance of your calves through your nutrition and activity.