Effects of Physical Therapy on Isometric Neck Retraction Strength and Pain in Patients With Neck Disability
Conditions: Neck Pain, Strength
Sponsor: Campbell University, Incorporated

Cover Page Study Protocol 
Date: 4/28/2022
All the information contained in this document including the Study Protocol and Statistical 
Analysis Plan are directly related to the study entitled: 
Effects of Physical Therapy on Isometric Neck Retraction Strength and Pain in Patients 
with Neck Disability  
NCT04334655 

The primary researcher Frank Tudini changed positions from Campbell University to The 
University of Tennessee at Chattanooga in August 2020. Campbell University provided oversight 
of this project until August 14th, 2020 and after August 14th 2020 the study was covered under 
the IRB of The University of Tennessee at Chattanooga (IRB # 20-082). Other than changing the 
name on the top of the consent form from Campbell University to The University of Tennessee 
at Chattanooga, no other changes were made to the methods or procedures.  
Study Protocol 
Four physical therapists (PT) from four different outpatient clinics will collect 
demographic, anthropomorphic, and isometric neck retraction strength data with an 
Hand Held Dynamometer (HHD) in patients with primary complaints of neck pain at the 
time of the initial evaluation, regular follow-ups, and at discharge. The PT will also 
include a shortlist of the primary interventions used during the course of treatment. A 
short video explaining how to test isometric neck retraction strength will be provided to 
each clinic and the description can also be found in the investigator's previous article 
entitled "Reliability and validity of measurements of cervical retraction strength obtained 
with a hand-held dynamometer." Basically, the patient will lay on their back with the 
HHD under the external occipital protuberance. The patient will then perform a practice 
isometric contraction at 50% maximum force followed by two maximum effort trials with 
1-minute in-between.
A follow-up phone call will be made to each clinic to assure that the units arrived and to 
answer any additional questions regarding the procedure or data to be collected. Follow 
up phone calls will then be performed monthly to assess progress. At the end of three 
months, a preliminary analysis, based on the total number of documented patients will 
be made. A power analysis indicates that 40 patients will be sufficient to answer our 
research question. This is based on a 2007 article by Cagnie, B. in the Archives of 
Physical Medicine Rehabilitation entitled "Differences in isometric neck muscle strength 
between healthy controls and women with chronic neck pain: the use of a reliable 
measurement." To account for drop-outs the investigators raised this to an n=60. 
Data will be collected over a secure Qualtrics server to which each participating PT will 
have an individual access code. No identifiable patient information will be given to the 
investigators. Data analysis will include Pearson or Spearman correlation coefficients to 
examine the relationship between isometric neck strength with patient-reported outcome 
measures including the Numeric Pain Rating Scale (NPRS) and Neck Disability Index 
(NDI). Repeat Measure ANOVA will be used to compare the variables including strength 
over different time frames throughout the episode of care. An intention to treat analysis 
will be used for patients who do not complete the study or their Physical Therapy (PT) 
care. 
Data will be collected on 60 consecutive patients with neck pain. Inclusion criteria 
include patients over the age of 18 years that are receiving physical therapy with 

primary complaints of neck pain. Exclusion criteria include individuals with a history of 
cervical neck surgery as well as those with neurologic diseases or Chronic Obstructive 
Pulmonary Disease (COPD). 
Day 1: Patient with a primary complaint of neck pain is seen in one of the four physical 
therapy clinics participating in the study. The patient is recruited by the PT in the clinic. 
The study will be explained to the patient and written consent obtained and filed in the 
clinic. A copy of the consent will also be given to the participant. 
The PT conducts their initial evaluation and treatment as they normally would with the 
addition of a test for isometric neck strength. Measuring neck strength is a normal 
procedure for a PT to perform and is well within the scope of practice for physical 
therapists. Many clinics do not have hand-held dynamometers (HHD) so we will be 
providing the dynamometers and mailing them to each clinic. The MicroFET2 hand-held 
dynamometer is FDA approved (Regulation number: 21 CFR 888.1240) and will be 
used only in the manner for which it was attended, i.e. to measure isometric strength. 
The hand-held dynamometer is placed in a cradle behind the patient's head in supine. 
Instructions are given to retract the chin and head into the dynamometer three times. 1 
practice trial at 50% and 2 maximum effort trials with 1 minute between attempts. This is 
outlined in the investigator's 2019 study (Reliability and validity of measurements of 
cervical retraction strength obtained with a hand-held dynamometer. Journal of Manual 
and Manipulative Therapy. 2019;27(4): 222-228.) The entire procedure will take 
approximately 5 minutes. This information is recorded along with anthropomorphic data, 
pain levels, neck disability index, and treatment performed. All information is coded and 
sent to the primary researchers over a secure Qualtrics connection. 
4. The patient will receive regular Physical Therapy care. The neck strength, pain, and
neck disability index are recorded at re-assessments (usually monthly) and at
discharge. The use of this assessment will in no way impact the quality or quantity of PT
received by the patient
Statistical Analysis Plan (SAP) 
The primary measure of interest in this study is neck retraction force. The average of 2 
trials will be used in all strength analysis. Secondary measures such as the Numerical 
Pain Rating Scale and the Neck Disability Index will be used to characterize the neck 
pain. Paired t-tests and standardized response mean will be used to describe the 
responsiveness of neck retraction forces in patients receiving therapy for neck pain. 
Convergent validity will be examined by calculating spearman correlations between 
baseline neck retraction force, numerical pain rating scale scores, and neck disability 
index scores (expressed as percentages).