This pilot study investigates the effectiveness of non-invasive brain stimulation (tDCS) in alleviating cancer-related fatigue (CRF) and muscle weakness. Using a randomized, double-blind crossover design, participants perform fatiguing muscle tasks with and without tDCS, and outcomes include task endurance, maximal voluntary contraction force, and neuromuscular markers. Neural mechanisms will be assessed via EEG, TMS, and MRI.

General Inclusion - All participants

1. Aged 40-80
2. Right Handed, as determined by the Edinburgh Inventory 21
3. Proficient in English
4. Must be available for the familiarization, and testing sessions

General Inclusion - Cancer Patients only

1. Cancer (>6 months post therapy)
2. Suffers from a subjective feeling of cancer related fatigue and weakness as assessed by the following question: "Do you suffer from symptoms of fatigue and weakness related to your cancer or cancer treatment?"
3. Have had cancer diagnosis and treatment in the past
4. Must have a stable physical/health condition for the past 3 months with no expected changes for the duration of the study

General Exclusion - All participants

1. Neurological, psychiatric, musculoskeletal or other types of disorder not caused by cancer and/or cancer treatment, which may affect participants sensorimotor function and cognitive abilities
2. No consciousness to understand and sign informed consent voluntarily
3. History of alcohol, and illicit drug use
4. History of smoking within the last 5 years.

General Exclusion - Cancer Patients 1. Radiation, surgery, chemo, or other cancer treatment therapies in the past 6 months prior to enrollment. Hormonal maintenance treatment is allowed.

General Exclusion - Healthy Participants

1. History of cancer or cancer treatment

Exclusion criteria related to tDCS and TMS safety - All participants

1. History of epilepsy or unprovoked seizures
2. Family history of epilepsy (father, mother, children, siblings with diagnosis of epilepsy)
3. Active migraine headaches
4. Past or current history of treated tinnitus or severe hearing problems
5. Implanted medical devices (pacemakers, defibrillators, medical pump, implanted brain stimulator, aneurysm clip, carotid or cerebral stents, central venous catheter, non-removable hearing aids)
6. Damage to the skin on the scalp
7. History of mental illness (schizophrenia, anxiety, major depression, manic disorders)
8. Tattoo with metal based ink in the head or neck
9. Currently taking or withdrawing from any central nervous system active medication (stimulants, anticonvulsants, antidepressants, psychotropic medications).
10. Pregnant as determined by a Pregnancy test for non-menopausal (no menstruation for at least 1 year) women younger than 55 years (for TMS and fMRI only).

Exclusion criteria related to MRI safety - All participants

We will be using the Kessler Foundation RONIC MRI center screening form to screen participants for the MRI scan. Exclusion criteria includes:

1. Suffer from claustrophobia (fear of confined spaces)
2. Prior injury to the eye involving a metallic object or fragment (e.g., metallic slivers, shavings, foreign body, etc.)?
3. Presence or prior injury by a metallic object, or foreign body or metallic fragment (e.g., BB, bullet, shrapnel, etc.)
4. Currently or former metal worker (welder, machinist, etc.)
5. Implanted electrical devices (e.g. pacemakers, defibrillators or ICD)
6. Implanted stimulators or internal electrodes or wires (neurostimulator, brain stimulator, spinal cord, bone growth/bone fusion)
7. Aneurysm clips (metal clips on the wall of a large artery), metallic stent, shunt (spinal)
8. Metallic prostheses or implants (including metal pins and rods, plate, screw, surgical staples, clips or metallic sutures, joint replacement (hip, knee), cochlear or other otologic implant, eye, penile, heart valves, eyelid spring or wires, prosthetic limbs)
9. Dental implants, dentures or partial plates (regular filling, amalgam and crown are OK)
10. Insulin, medication or other infusion pumps
11. Radiation seeds or implants
12. Transdermal medication patch (Nitroglycerine, Nicotine)
13. IUD, diaphragm or pessary
14. Tissue expander (e.g. breast)
15. Body tattoos or permanent makeup (eyeliner, lip) if deemed unsafe in the MRI
16. Body piercing