Combined Application of Electrical Stimulation and Volitional Contractions for Muscle Strengthening and Knee Pain Inhibition (Seated Study)

Arthritis is the most common cause of disability in the United States. Approximately 42.1% of
women and 31.2% of men over the age of 60 have knee osteoarthritis (KOA). KOA is associated
with pain, quadriceps weakness, swelling, instability, decline of range of motion, physical
function, and quality of life (QOL). The presence of KOA significantly decreases QOL, while
quadriceps strengthening has the ability to improve QOL. However, one challenge with
strengthening is that knee pain influences muscle strength and physical function. Not only
quadriceps strengthening but also reduction of knee pain may be necessary to reduce
functional limitations from KOA. However, at this time, there is insufficient evidence
regarding effective training to not only increase quadriceps strength but also reduce knee
pain and improve neural function. Thus, there is a need for interventional studies to build
on observational findings to evaluate the relationships of neural function, knee muscle
strength, knee pain, and physical function.

The critical barrier to studying whether quadriceps strengthening is protective against
worsening physical function is the lack of an effective strengthening program for people at
elevated risk for KOA. Factors that place older adults at elevated risk for symptomatic KOA,
(e.g. sedentary lifestyle, obesity, knee pain, knee injury or surgery), may also contribute
to reduced tolerance of high load quadriceps strengthening programs. If a well-tolerated and
effective means of strengthening could be identified, it may also have additional benefits in
reducing knee pain, improving physical function and avoiding disability in individuals with
or at risk of KOA.

Neuromuscular electrical stimulation (NMES) is widely used to strengthen muscles and improve
function in people who cannot exercise at medium-high intensity. For KOA, NMES is effective
for enhancing quadriceps strength, knee pain, physical function. Therefore, NMES could
contribute to decreased neural inhibition from knee pain and promote muscle function (e.g.
muscle strength, power, contraction speed, and co-contraction). Recently, it was reported
that the combined application of NMES and volitional contractions (NMES-VC) is effective for
making up for a limitation of NMES. NMES-VC could help to improve motor recovery. The results
of recent studies suggest that a hybrid training system that utilizes both volitional
contractions and NMES simultaneously, might be an effective method that can improve physical
function by strengthening muscles and relieving knee pain in people at risk for incident or
progressive symptomatic KOA.

This line of research could have a significant positive impact on public health, by leading
to the introduction of an inexpensive means of well-tolerated and safe exercise that can be
completed in community rehabilitative environments. Successful completion of this initial
investigation will enable pursuit of research to determine whether NMES-VC is effective in
quadriceps strengthening and pain relief while improving neural function in symptomatic and
progressive KOA. Reduction of this primary cause of disability through cost-effective
preventive exercise has a high potential to reduce the burden of disease and disablement,
thereby improving the quality of life for older adults and significantly reducing the costs
to individuals and society.

The specific aim of the proposed research is to assess the efficacy of a twelve-week,
efficient and tolerable, low-intensity exercise program with NMES-VC for improving quadriceps
strength, knee pain and physical function in women with risk factors for incident symptomatic
or progressive KOA. This specific aim will be achieved through a randomized, controlled
trial, comparing low intensity exercise with and without NMES-VC. This research is novel in
that it will be the first to use a low load regimen that will minimize the potential for
adverse loading on the knee joint while still having a high likelihood to lead to clinically
meaningful strength gains, pain relief and physical function improvement in older adults at
elevated risk for symptomatic or progressive KOA.

Inclusion Criteria:

1. Female

2. Age 40-85 years

3. One or more of the following:

1. Knee symptoms (pain, aching, or stiffness) on most of the last 30 days;
categorically defined, so all severity of symptoms ok, but must have knee
symptoms on most days

2. History of knee injury or surgery

3. Body Mass Index (BMI) greater than or equal to 25 kg/m2

4. BMI less than 45 kg/m2

Exclusion Criteria:

1. Knee injection within 6 weeks prior to the study

2. Resistance training at any time in the last 3 months prior to the study

3. Bilateral knee replacement

4. Lower limb amputation

5. Lower limb surgery in the last 6 months that affects walking ability or ability to
exercise

6. Back, hip or knee problems that affect walking ability or ability to exercise

7. Unable to walk without a cane or walker

8. Inflammatory joint or muscle disease such as rheumatoid or psoriatic arthritis or
polymyalgia rheumatica

9. Multiple sclerosis or other neurodegenerative disorder

10. Known neuropathy

11. Self-report of Diabetes

12. Currently being treated for cancer or having untreated cancer

13. Terminal illness (cannot be cured or adequately treated and there is a reasonable
expectation of death in the near future)

14. Peripheral Vascular Disease

15. History of myocardial infarction or stroke in the last year

16. Chest pain during exercise or at rest

17. Use of supplemental oxygen

18. Inability to follow protocol (e.g. lack of ability to attend visits or understand
instructions)

19. Staff concern for participant health (such as history of dizziness/faintness or
current restrictions on activity)

20. Unable to attend 12 or more sessions during the study

21. Implanted cardiac pacemaker, spinal cord stimulator, baclofen or morphine pump or
other implanted electrical device.

22. Dermatitis or skin sensitivity.

23. Pregnancy