Exercise responses in elite male wheelchair athletes with or without cervical spinal cord injury.

Introduction:

Salivary alpha amylase (sAA) and chromogranin A (sCgA) have both been suggested as non-invasive markers for sympathetic nervous system (SNS) activity. sAA activity is responsive to exercise, particularly that of a high-intensity nature, supporting the relationship between sAA and SNS activity. In response to acute exercise stress, sCgA shows a similar response to sAA. However, the correlation to physiological responses during acute exercise has been shown to be stronger for sCgA than for sAA.

A complete cervical spinal cord injury leading to tetraplegia is accompanied with sympathetic dysfunction. Increases in sAA activity have been found previously in both cervical- and thoracic-level athletes with SCI and non-spinal injured controls following strenuous exercise, which further questions sAA as a true indicator of central sympathetic drive.

Study aim: To establish the exercise response of non-invasive markers for sympathetic nervous system in wheelchair athletes.

Methods:

Twenty-six international-level male wheelchair athletes (Tetraplegia (TETRA), N = 8, Paraplegia (PARA), N = 10 and disabilities unrelated to SCI (non-spinal injured (NON-SCI), N = 8). All participants with SCI had a motor and sensory complete lesion in accordance with the American Spinal Injury Association (ASIA) impairment scale.

Participants performed exercise to exhaustion on a treadmill. Saliva and blood samples were taken pre, immediately post, and 30-min post exercise and analysed for Salivary alpha amylase (sAA), chromogranin A (sCgA) and plasma adrenaline concentration, respectively.

Main findings:

• Both sAA and sCgA concentrations increased following exhaustive exercise in all spinal injury level subgroups; (P < 0.05).
• Plasma adrenaline concentration was significantly lower in TETRA when compared with the other subgroups with intact sympathetic function (P < 0.001).
• The blunted post-exercise rise in sAA and adrenaline in tetraplegia implies that both reflect SNS activity to some degree.
• Whilst plasma catecholamine concentrations represent a gold standard with respect to SNS activity, sAA activity may be used to help indicating SNS dysfunction in an exercise context.
• sAA may be referred to as a marker which partly reflects SNS activity but is also regulated by other mechanisms.
• This study favours the use of alpha amylase over chromogranin A as a surrogate marker for sympathetic activity.

Reference

Leicht CA, Paulson TAW, Goosey-Tolfrey VL, Bishop NC. Salivary alpha amylase not chromogranin A reflects sympathetic activity: exercise responses in elite male wheelchair athletes with or without cervical spinal cord injury. Sports Med Open. 2017 Dec;3(1):1. doi: 10.1186/s40798-016-0068-6.

Image credit: © Paralympics GB