Table 4.

Mechanical and electrical stimulation protocols used for skeletal muscle construct maturation

Author	Cell type	Scaffold material	Stimulation protocol	Outcomes
Mechanical stimulation
Aguilar-Agon et al. [104]	C2C12 Myoblasts	Collagen hydrogel	Progressive load to 15% strain over 1 h, 2 h isometric tension.	Myotube diameter and maximal contractile force increased at 45 h post loading.
Heher et al. 2015 [105]	C2C12 Myoblasts	Fibrin hydrogel	10% static strain for 6 h, 3% static strain for 18 h rest period. 6 days training	Strain-induced cell and actin alignment. Increased myotube diameter, length and differentiation.
Candiani et al. 2010 [107]	C2C12 Myoblasts	Electrospun DegraPol®	3 days unidirectional strain (3.3%) followed by 10 days cyclic strain (0.5 Hz, 3.4% strain, 28 min rest period)	Enhanced myosin heavy chain expression in myoblasts subjected to dynamic strain protocol vs. static strain alone
Matsumoto et al. [108]	C2C12 Myoblasts	Fibrin hydrogel	Static strain (0–200%)	Myofibers aligned along the axis of strain. Myoblast proliferation increased with increasing strain
Electrical stimulation
Patel et al. [52]	C2C12 Myoblasts	Collagen I or Laminin-111	1 V, 2 ms pulses at 2 Hz, 1 h/day for 3 days	Electrical stimulation increased expression of MyoD and myogenin during differentiation.
Khodabukus et al. [53]	Human Myocytes (minced muscle)	Matrigel (BD Biosciences)	70 mA, 2 ms pulses at 1 Hz or 10 Hz. 1 h stimulation, 7 h rest period. 7 days training	Stimulation increased myobundle size, sarcomere proteins and contractility. 10 Hz stimulation resulted in greater hypertrophy vs. 1 Hz.
Ito et al. [49]	C2C12 Myoblasts	Matrigel and collagen	0.3 V/mm, 4 ms pulse width at 1 Hz. 10 days training	4.5-fold increase in force generation at day 14 compared to constructs without electrical stimulation
Donnelly et al. [54]	C2C12 Myoblasts	Fibrin hydrogel	1.25–5 V/mm, 4 pulses of 0.1 ms, 3.6 s recovery, 7 days training	Greatest force production at 2.5 v/mm
Electromechanical stimulation
Kim et al. [106]	C2C12 Myoblasts	Fibrinogen and matrigel	2.3% strain over 4.3 s. 2.5 v/mm, 1 ms pulses, 0.1–0.5 Hz. In-phase vs. out-of-phase electromechanical stimulation. 3 min or 20 min training.	Out-of-phase electromechanical stimulation resulted in greater improvement in construct force generation than either in-phase, or separate electrical and mechanical stimulation.
Liao et al. [51]	C2C12 Myoblasts	Electrospun diisocyanate-based polyurethane fibres	5% or 10% cyclic strain at 1 Hz for 1 h, 5 h rest period. Electrical stimulation 20 V, 10 ms pulse width. Between days 2 and 14 post differentiation.	Increased MHC and percentage of striated myotubes under electromechanical stimulation. Electrical stimulation at early timepoints was detrimental to myotube development. Cyclic strain alone promoted proliferation over differentiation.