The Effects of Iyengar Yoga on Stability in Adults with Down Syndrome
Written by Mike Curtin
Down Syndrome is an intellectual disability with distinct physical characteristics caused by a mutation of the 21st chromosome via nondisjunction. Nondisjunction is when one or more pairs of homologous chromosomes separate during cell division resulting in an abnormal distribution of chromosomes in the daughter cells. Down Syndrome can be divided into three unique types; Trisomy 21 (nondisjunction), Mosaicism, and Translocation. Down Syndrome has both intellectual and physical symptoms. Intellectual symptoms include: delayed learning, delayed speech and language development, impulsive behavior and short attention spans. Physical Symptoms include Obstructive Sleep Apnea (OSA), various cardiovascular conditions, vision and hearing loss, hypotonia and hypermobility.
The combination of hypotonia (low muscle tone) and hypermobility can be problematic. Essentially, this combination creates above average ranges of motion with below average stability and strength; a recipe for injuries and falls. In regards to the implementation of Iyengar Yoga, our goal was to create stability and strength throughout ranges of motions through a combination of isometric holds using closed kinetic chain exercises to build both strength and stability.
The benefits of isometric muscle contractions have been well documented. In the strength and conditioning world, Cal Dietz from the University of Minnesota has popularized them through his Triphasic Training manual. An isometric contraction is a static contraction of a muscle, where the muscle is contracted, but the muscle does not change in length. Studies have shown that isometric muscle contraction recruits more motor units (motor neuron and the skeletal muscle it innervates) than both eccentric and concentric contractions. Isometrics activated 95.2% of the motor units while eccentric and concentric contractions stimulated 88.3% and 89.7% respectively (Babault et al. 2001). It’s important to understand, that isometric training only provides strength gains at the joint angles being worked. Although some view this as a limitation of isometric training, it can also provide an efficient way to strengthen a desired movement pattern at a specific range of motion.
For example, Vimanasana (warrior 1) was selected because it provides an isometric hold in an extremely relevant position to functioning in everyday life. This position resembles an exaggerated stride or shallow lunge which tends to be an unstable position for people with hypotonia and hypermobility. However, by holding vimanasana (warrior 1), our athletes can contract muscles and stimulate motor units, making them stronger in a typically unstable position. Over time, using isometrics in unstable positions through Iyengar yoga should provide increased strength via increased motor unit recruitment. The Salabhasana pose incorporates isometric contractions of the gluteus maximus and hamstrings, as well as the spinal extensors which provide strength in extended positions such as reaching overhead.
It is also important to mention that Vimanasana is a closed kinetic chain movement, meaning that the distal portion of the body, in this case, the feet, are in contact with the ground.. Loading multiple joints through closed chain exercises are reported to increase proprioception and balance (Bleacher, Ellenbecker 2012). Increasing proprioception and mechanoreceptor stimulation through closed chain movements like Vimanasana will increase balance and decrease the incidence of falls.
The logic for incorporating yoga into the fitness routine of individuals with Down Syndrome is straightforward and the science (although no literature exists for this population) would seem to support it. However, through two weeks of implementing the routine one issue seem to be present. An isometric contraction is more than just passively sitting in a certain position; it requires an active muscle contraction to resist movement. This is something that can be difficult to communicate and requires the athlete to be kinesthetically aware of where their body is in space and how it is functioning. Time will tell whether there are any noticeable improvements in our athletes’ ability to consciously contract in a given position. Regardless, I believe yoga to be an effective replacement for stretching in the Down Syndrome population, or for any hypermobile athlete.