Timing and dosage of FES cycling early after acute spinal cord injury: A case series report

Figures & data

Figure 1 FES cycling progress and muscle cross-sectional area changes. DPI, days post injury. CSA, cross-sectional area. Changes from baseline are expressed as a percentage. The result section in the text describes the average power production. For purpose of comparison with other studies, resistance data are also provided in the figure. P1 showed small changes in muscle CSA in the first 6 weeks of low-intensity FES cycling. Overall, P1 gained muscle mass in the stimulated thigh muscles (quadriceps and hamstrings), and lost muscle mass in the non-stimulated calf muscles. At 13.3 weeks, muscle CSA was increased in right and left thighs (16% and 2%, respectively), and decreased in right and left calves (6% and 13%). P2 showed an initial loss in muscle CSA at 2.1 weeks (about 4–5% in left/right calves, and 5–11% in thighs), but regained about 6–7% in calf muscle CSA, and 9–12% in thigh muscle CSA after 6.1 and 8.7 weeks of FES cycling, respectively. P3 showed loss in muscle CSA up to 6 weeks (about 11–13% in calves, and 15% in thighs), and regained some muscle CSA at 8 weeks in calves and left thigh. The sudden apparent increase in left thigh CSA at 4 weeks was due to an increase in thigh circumference with unknown reason. The sudden apparent increase in right thigh CSA at 8 weeks was due to swelling from a diagnosed heterotopic ossification in the right proximal medial thigh. FES cycling was discontinued at 8 weeks, resulting in the decreases in CSA at the 12-week assessment.

Table 1 Participant information, start and duration of FES cycling.

	Age (Years)	Sex	Height (m)	Weight (kg)	BMI (m/kg^2)	AIS	NLI	Cause	Start FES Cycling (Days PI)	Transfer Rehab (Days PI)	FES Cycling Duration
											(Weeks)	(Sessions*)
P1	25	M	1.80	75	23.1	B	T4	Vascular	17	25	13.4	36 (5)
P2	38	M	1.68	68	24.1	C	C4	Traumatic	20	39	11.9	32 (7)
P3	24	F	1.63	57	21.5	A	T4	Traumatic	16	22	8.0	20 (2)
Mean	29.0		1.70	66.7	22.9				17.7	28.7	11.1	29.3 (4.7)
Total												88 (14)

Note: FES, functional electrical stimulation; BMI, body mass index; AIS, American Spinal Injury Association Injury Scale; NLI, neurological level of injury; m, meter; kg, kilogram; PI, post injury; P, participant number; F, female; M, male; T, thoracic; C, cervical.

Transfer Rehab is the time of transfer from acute care hospital to rehabilitation hospital, expressed relative to the time of injury (days post injury).

FES Cycling duration is the total number of weeks FES cycling was performed.

*FES Cycling Sessions gives the total number of sessions performed, with the number of sessions performed in the acute care hospital in between brackets.

Table 2 FES stimulation parameters for first and best session.

				Quads		Hams		Gluteals		Gastrocs
	PW (µs)	Freq (Hz)	Stim (µC)	L (mA)	R (mA)	L (mA)	R (mA)	L (mA)	R (mA)	L (mA)	R (mA)
First FES Session
P1	300	35	11.8	35	35	50	50	50	55
P2	300	35	8.8	22	24	30	30	35	35
P3	300	35	19.0	60	60	60	60	70	70
Best FES session
P1	300	35	22.7	105	105	80	80	105	105
P2	300	40	15.2	85	123	52	52			55	52
P3	300	35	22.0	119	140	75	75	70	70	67	67

Note: FES, functional electrical stimulation; Quads, quadriceps; Hams, hamstrings; Gastrocs, gastrocnemius; PW, pulse width, Freq, stimulation frequency; Stim, Average stimulation; L, left; R, right; µs, microseconds; Hz, hertz; µC, micro Coulomb; mA, milliampere; P, participant.

Best session is the session with the highest average power of all sessions per participant. Average stimulation is the average charge delivered per session across all channels, and is an overall measure of the stimulation intensity for the session. Underlined values in bold indicate stimulation amplitudes that were limited due to stimulation-associated pain. Underlined values indicate stimulation amplitudes that were limited due to apprehension with FES. Value in bold and italic indicate a deviation from the default parameter.

Table 3 FES cycling performance for first and best session, and progress to OffMotor and voluntary cycling.

	First FES Session			Since FES Cycling Start
	Power (W)	OffMotor (Min)		OffMotor >90% (Weeks)	Voluntary Cycling (Weeks)
P1	0	0		7.1	No
P2	0	0		5.0	11.1
P3	0	0		1.6	No
		Best FES Session
	Weeks	Duration	OffMotor	Velocity	Avg.Power	Max.Power	Avg.Res
		(Min)	(Min)	(RPM)	(W)	(W)	(Nm)
P1	13.0	45	40:00	40–55	13.9	19.4	3.5
P2	11.1	35	33:42	30	8.8	13.0	2.8
P3	6.9	35	34:03	30	19.0	24.2	6.1

Note: FES, functional electrical stimulation; Avg, average; Max, maximum; Res, resistance; W, Watts; Min, minutes; RPM, revolutions per minute; Nm, newton meter; P, participant.

Best session is the session with the highest average power of all sessions per participant. OffMotor is the time in minutes per session biked without motor support, i.e. with FES-produced or voluntary muscle contraction. Underlined values indicate a session including interval training with fast passive cycling, therefore OffMotor time is only fraction of total time, and velocity gives low and high RPM used.