Spinal Manipulation and Neuromuscular Performance on Amateur Cyclists

The present study will follow a parallel, pre-post design. The aim will be to determine the acute effects of spinal manipulation therapy (SMT) on different neuromuscular properties of recreational cyclists. Specifically, the investigators will measure the maximum force production capacity and muscle activation of the knee extensors concomitantly during a maximal voluntary contraction, as well as the maximum and mean power attained during a Wingate cycling test (i.e., 30 seconds 'all out'). Participants will undergo the tests on two different occasions separated by at least 48 hours and a maximum of 2 weeks. The same tests will be conducted in both testing sessions, but participants will be randomly assigned into two groups (sham or actual SMT) immediately before the second testing session.

• Spinal manipulative therapy (Procedure), also known as Chiropractic manipulation, Spine thrust manipulation: Participants in the actual spinal manipulative therapy group will be assessed through the activator basic method protocol. SMT will be performed with an Activator IV (Activator Methods International, Phoenix, AZ) setting the force at level 3 for the low thoracic spine (T7-T12), and level 4 for the lumbar spine and pelvis.
• Sham spinal manipulative therapy (Other): Participants in the sham SMT group will undergo a protocol identical to the actual one, with the exception that a sham mechanical thrust (force set at level 0) will be delivered to the targeted areas. In the force level 0 no excursion of the stylus occurs, but the instrument produces the same clicking sound as in the actual SMT condition

Primary outcomes

• Maximal force [On the control session and on the intervention session (immediately after the sham or actual SMT procedure)]: Peak force registered during an isometric maximal voluntary contraction of the knee extensors.
• Voluntary activation [On the control session and on the intervention session (immediately after the sham or actual SMT procedure)]: Electromyographic activity of the vastus lateralis muscle registered during an isometric maximal voluntary contraction of the knee extensors.
• Peak power [On the control session and on the intervention session (immediately after the sham or actual SMT procedure)]: Peak power registered during a 30-second Wingate anaerobic cycling test
• Mean power [On the control session and on the intervention session (immediately after the sham or actual SMT procedure)]: Mean power registered during a 30-second Wingate anaerobic cycling test

Sex: Male, ages: 18 Years to 45 Years, accepts healthy volunteers

Inclusion Criteria:

* Will be recruited from three different local triathlon and cycling clubs.
* Will have to cycle at least 4 hours per week during the preceding 3 months, and to have a cycling experience greater than 2 years

Exclusion Criteria:

* Having suffered an injury in the month before the study that precluded regular exercise practice
* Having suffered any type of spine injury before the study
* Having previously received Spinal Manipulation Therapy

• Valenzuela PL, Pancorbo S, Lucia A, Germain F. Spinal Manipulative Therapy Effects in Autonomic Regulation and Exercise Performance in Recreational Healthy Athletes: A Randomized Controlled Trial. Spine (Phila Pa 1976). 2019 May 1;44(9):609-614. doi: 10.1097/BRS.0000000000002908. PMID 30325889

• Study Protocol and Statistical Analysis Plan (PDF, 2019-01-14)

• Pedro de la Villa, MD, PhD, Study director, University of Alcalá