Acute Effects of Spinal Manipulation on the Neuromuscular Performance of Amateur Cyclists: Pilot Study
Phase: NA
Conditions: Manual Therapies
Sponsor: University of Alcala

Title: “Acute effects of spinal manipulation on sports performance in amateur 
cyclists. Pilot study” 
 
Title (spanish): “Efectos agudos de la manipulación espinal en el rendimiento 
deportivo en ciclistas amateur. Estudio piloto” 
 
 
 
 
Date: January, 14    2019 
 
 

 
Introduction 
Spinal manipulative therapy (SMT), which consists on the application of high-speed, 
low-amplitude movements, slightly above the range of passive movement of the spinal 
joints (Bronfort, Haas, Evans, & Bouter, 2004), is widely used for the treatment of 
various musculoskeletal conditions such as acute or chronic back pain, having shown 
that it provides benefits both in terms of pain and function (Bronfort et al., 2004; Gross 
et al., 2015; Paige et al., 2017).  
The use of the SMT is also expanding to the sports field, being used by many athletes 
before their competitions, trusting in a potential ergogenic effect. In fact, greater 
corticospinal excitability and greater electromyographic activity have been observed 
acutely after a single session of SMT (Christiansen et al., 2018; Niazi et al., 2015), 
effects that could result in greater muscle strength and ultimately in better sports 
performance. 
However, the evidence regarding the benefits of SMT in performance is scant and 
contradictory. Some studies have observed greater muscular strength both in subjects 
with spinal dysfunction (Niazi et al., 2015) and in elite athletes (Botelho & Andrade, 
2012; Christiansen et al., 2018). On the contrary, others did not find benefits in muscle 
force (Humphries et al., 2013; Sanders et al., 2015). Neither have benefits been 
observed in a running incremental test (Ward et al., 2012) or in other specific sports 
actions such as jumping or sprinting (Shrier, Macdonald, & Uchacz, 2006). Therefore, 
there is still not enough evidence to support the ergogenic role of this technique for the 
acute improvement of sports performance. 
In a recently published study, an increase in parasympathetic modulation of the 
autonomic nervous system was found after performing SMT with Activator throughout 
the entire spine (at the discretion of the chiropractic specialist) (Valenzuela, Pancorbo, 
Lucia, & Germain, 2018). However, no acute benefits in performance were observed. 
Given these results, we hypothesized that the absence of such benefits could be due to 
the global manipulation of the spine, instead of a specific action on the segments related 
to the dorsal roots that innervate the lower limbs. The aim of the present project is to 
verify if SMT performed on the dorsal roots of the lumbar segments is able to enhance 
the neuromuscular performance of the lower limbs in amateur cyclists.  

Hypothesis 
Our hypothesis is that SMT performed on the dorsal roots of the lumbar segments is 
able to improve neuromuscular performance, improving the maximum force, power or 
muscle activation, or at least reducing the perceived effort to achieve the same 
performance. 
Objectives 
- General objective: To determine the effects of SMT on neuromuscular performance in 
athletes. 
- Specific objective: To determine the effects of SMT on muscle strength, voluntary 
activation and power. 
Methodology 
Participants 
In this pilot study we will try to include 40 participants. Participants will be recruited 
from local sports clubs. The inclusion criteria will be: being male between 18 and 45 
years old, training a minimum of 3 hours per week, and not having received SMT in at 
least one year. The exclusion criterions will be: having suffered an injury or illness 
during the two months prior to the test, or having been unable to maintain the usual 
training rhythm during the previous month. Prior to their participation, the subjects must 
sign an informed consent form after reading the corresponding information sheet of the 
study. 
Experimental design 
The present study will follow a randomized, double-blind (participant and assessor), 
parallel and sham-controlled design. Participants must attend to the facilities twice; and 
these visits will be separated by 7 days. Subjects will be randomly assigned to receive 
the actual SMT intervention or a sham intervention. Once randomized, all participants 
will make a first control visit in which the tests will be carried out without receiving any 
type of intervention. At the second visit, the corresponding treatment (real or sham) will 
be applied before the tests. Each subject will perform the tests at the same time of day. 
Participants should maintain their eating habits during the experimental period, as well 

as to avoid caffeine consumption and physical exercise in the 48 hours prior to each 
visit. 
Measurements 
The descriptive and anthropometric variables of the athletes will be measured by means 
of a scale and a stadiometer. We will also ask participants about the number of hours 
that they usually train per week. 
Subsequently, participants will perform an isometric maximum voluntary contraction 
(MVC) with the knee extensors. Specifically, they will perform tree 5-second 
repetitions with the dominant leg, and the maximum force attained will be measured by 
means of a handheld dynamometer (microFET®2, Hoggan Scientific). The highest 
force reached in these contractions will be used for analysis. In addition, the maximum 
activation level of the vastus lateralis muscle will be also assessed by means of surface 
electromyography (ML856 PowerLab 26T, LabChart, ADInstruments, New Zealand) 
during these MVCs. 
Muscle power and overall ‘anaerobic’ performance will be assessed by means of the 
Wingate test, performed on a cycle ergometer with electromagnetic brake (Cardgirus 
Medical, Bikemac, Sabadell, Spain). This test, one of the most popular for the 
evaluation of anaerobic power (Driss & Vandewalle, 2013), will last 30 seconds. 
Participants should try to achieve the maximum possible power during the test. We will 
analyze both the peak power (greatest power reached in periods of 1 second) and the 
mean power attained during the test. In addition, immediately after the test we will 
assesses the rating of perceived exertion on a 1-10 scale (Borg, 1998). 
Intervention 
The actual SMT intervention will always be performed by a chiropractic specialist, 
while the placebo intervention will be performed by the other chiropractor. The actual 
SMT intervention will consist of spinal manipulation with high velocity and low 
amplitude movements. Participants will be evaluated according to the basic Activator 
protocol (Fuhr, 2005). This protocol consists of the visual evaluation of possible 
differences in the length of the legs by performing maneuvers with the participant in 
prone position. These maneuvers are performed to locate the spinal areas that may 
present a possible dysfunction, applying a manipulation in these areas with the 

Activator instrument (AAI IV, Activator Methods International, Ltd, Phoenix, AZ). 
This instrument will allow us to exert the same pressure on all subjects. In the actual 
SMT intervention the Activator will be placed in the force position 4, which exerts a 
pressure of very short duration (5 ms) and a force peak of approximately 176 N. 
In the sham SMT condition all the maneuvers and evaluations will be carried out as in 
the actual SMT one. However, the Activator will be placed in the 0-force position, 
which means that the instrument will generate noise, but practically no movement will 
occur (approximately 19.5 N). Neither in the sham nor in the actual SMT intervention 
there are physical or mental risks for the participant, which is why they are considered 
non-invasive procedures. 
Although the chiropractors who administer the interventions (real SMT or placebo) will 
know the condition assigned to each participant, the latter and the researchers in charge 
of the outcomes assessment and of the statistical analysis will remain blind to this 
information. As it is not a cross-over study (each participant is tested after only one 
condition, actual or sham SMT), the participants will not know the real pressure that the 
Activator instrument exerts. Therefore, all participants will believe that they are 
receiving the actual SMT intervention.  
Statistical analysis 
The normality of the data will be checked using the Shapiro-Wilk test. In case the data 
present a normal distribution, differences between conditions will be analyzed by means 
of a two-way analysis of variance (ANOVA) test (intervention [real or placebo] x time 
[pre and post]). In case of non-normal distribution, we will try to make a logarithmic 
transformation of the data prior to the analysis of differences to achieve a normal 
distribution. If the non-normality of the data is maintained, the differences between 
interventions will be analyzed using the Friedman test. The analysis will be carried out 
with a statistical analysis software (SPSS 23, USA) setting the level of significant at 
p<0.05. 
 
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