My dad has been in a chair for 40 years.
I'm a walking person.

What This Is

FES (functional electrical stimulation) cycling uses surface electrode pads on paralyzed leg muscles to make them contract in sequence, pedaling a bike. It maintains muscle mass, bone density, cardiovascular health, and neuromuscular junction viability — even with zero voluntary control. Commercial FES bikes cost $15,000–$30,000. You can build one for under $500.

What You Need

Electrode Placement

1. Quadriceps (front of thigh): One pad on the proximal (upper) quad, one on the distal (lower) quad, about 4–6 inches apart. Place over the muscle belly — you can feel it as the thickest part of the front thigh. This extends the knee (pushes the pedal down).
2. Hamstrings (back of thigh): One pad on the upper hamstring just below the glute fold, one on the lower hamstring just above the back of the knee. This flexes the knee (pulls the pedal up).
3. Tibialis Anterior (front of shin): One pad just below and lateral to the knee, one about 4 inches down the shin. This dorsiflexes the ankle (lifts the foot, prevents foot drop during the upstroke).
4. Gastrocnemius (calf): One pad on each head of the calf muscle. This plantarflexes the ankle (pushes the toe down during the power stroke). Optional but helps with pedaling efficiency.

Timing Sequence — Which Muscles Fire When

Think of the crank as a clock. 12 o’clock = pedal at the top. 6 o’clock = pedal at the bottom.

1. 12 to 5 o’clock (power phase): Quadriceps ON — extending the knee, pushing the pedal down. This is where the work happens.
2. 4 to 8 o’clock (transition): Quads OFF, hamstrings ON — pulling the pedal through the bottom of the stroke and starting the upstroke.
3. 7 to 12 o’clock (recovery phase): Hamstrings ON, tibialis anterior ON — pulling the pedal up and keeping the foot from dropping.
4. Throughout: Calf fires briefly at 3–5 o’clock to assist the power phase. Optional.

Left and right legs are 180° out of phase — when left quads fire, right hams fire, and vice versa.

Method A — Manual Switching (No Electronics)

1. Secure feet to pedals with straps. Stabilize knees with lateral supports or a towel roll.
2. Set both NMES units to: frequency 35 Hz, pulse width 300 μs, ramp-up 1 second, hold time 5 seconds, ramp-down 1 second, rest time 5 seconds.
3. Start with low amplitude (20–30 mA). Increase until you see a visible contraction that actually moves the pedal. This might be 50–100+ mA depending on the person.
4. Channel 1 (unit 1): right quads. Channel 2 (unit 1): left hams. Channel 1 (unit 2): left quads. Channel 2 (unit 2): right hams. Set the two units so their on/off cycles alternate — when unit 1 is ON, unit 2 is OFF.
5. The alternation creates a basic pedaling motion. It won’t be smooth at first. The bike’s flywheel momentum helps carry through the dead spots.
6. Session: 20–30 minutes, 3 times per week. Increase to 45–60 minutes as tolerance builds.

Method B — Arduino-Controlled Automatic Switching

1. Mount a magnet on the crank arm. Mount a Hall effect sensor on the frame so it triggers once per revolution at the 12 o’clock position.
2. Wire the Hall sensor to an Arduino digital input. Wire 4 relay channels to Arduino digital outputs. Wire each relay in series with one stimulator channel’s electrode leads.
3. Program the Arduino to: detect the magnet trigger (crank at top), then switch relays on/off based on timing fractions of the revolution. E.g., if one revolution takes 2 seconds, right quads ON from 0–0.8s (12–5 o’clock), right hams ON from 0.7–1.4s (4–8 o’clock), etc.
4. Set all stim channels to continuous mode (no built-in cycling) and let the Arduino handle the timing via relays.
5. Calibrate by turning the crank slowly by hand and watching which muscles fire when. Adjust timing offsets until the sequence produces smooth pedaling.

Safety

• Autonomic dysreflexia (AD): If your injury is T6 or above, monitor for AD during every session. Sudden headache, flushing, high blood pressure, sweating above the injury level = STOP immediately. Sit upright, remove electrodes, check for triggers (electrode pinching skin, full bladder, tight straps).
• Skin checks: Inspect skin under every electrode pad before and after each session. Red marks lasting >30 minutes after pad removal = reduce intensity or reposition pads. Never place pads over broken skin, pressure injuries, or bony prominences.
• Fracture risk: Bones below the injury level lose density. In the first 2–4 weeks, use very low resistance on the bike and low stimulation intensity. Let the bones adapt to loading gradually. If you have known osteoporosis (DEXA T-score < -2.5 at femoral neck), consult your doctor before starting.
• Burns: Ensure full pad contact with skin. Air gaps concentrate current and can cause burns. Replace pads when they lose stickiness. Never use damaged pads.
• Spasms: If a muscle spasms hard during cycling, reduce intensity for that channel. A controlled contraction is the goal, not a maximal spasm.
• No pacemakers or implanted stimulators in the current path without medical clearance.

Progression

1. Weeks 1–2: 15–20 minutes, 3x/week, zero or minimal bike resistance. Focus on getting the timing right and finding the right stim intensity for each muscle group.
2. Weeks 3–4: 25–30 minutes, 3x/week. Add slight resistance. Increase stim amplitude if needed to maintain pedaling against resistance.
3. Month 2+: 30–45 minutes, 3–5x/week. Gradually increase resistance. Target 40–60 RPM. Track total distance or revolutions per session.
4. Month 3+: 45–60 minutes if tolerated. Some people add tibialis anterior and calf channels at this stage for a more complete pedaling pattern.
5. Ongoing: This is maintenance. The goal is consistency, not intensity. 3x/week minimum, indefinitely. Muscle and bone benefits require ongoing stimulation — they regress if you stop.

What to Expect

• Week 1: Muscles will fatigue in 5–10 minutes. This is normal. Paralyzed muscles have converted to fatigue-prone fast-twitch fibers. They’ll convert back with training.
• Month 1: Visible increase in muscle bulk in quads and hams. Legs will look different. Skin color may improve (better circulation).
• Month 3: Measurable increase in pedaling duration and resistance tolerance. Reduced spasticity in many people. Improved bowel regularity (the cycling motion helps).
• Month 6+: Bone density stabilization (DEXA-measurable). Cardiovascular improvement. Some people report reduced neuropathic pain.
• Does not require voluntary control. The stimulator does all the work. If voluntary signals start to emerge during cycling, that’s a bonus worth documenting and reporting to your care team.