Mechanical factors tune the sensitivity of mdx muscle to eccentric strength loss and its protection by antioxidant and calcium modulators

Table 1 ECC protocols in research for testing susceptibility of isolated male mdx EDL muscle to force loss

Parameter	Allen [19]	Brooks [20]	Faulkner/Chamberlain [21, 22]	Davies [23]	Duan [24]	Gailly [25]	Lowe/Ervasti [16,26,27,28]^c	Lynch [29]^c	Marechal [6]^c	Mendell/Janssen [30, 31]	Morley/Head [32]	Sweeney/Barton [5, 33]^c
Mouse age (converted to nearest month)	2–3	5	1–2^a [21] 7–10^a [22]	2–3	2–3	3–4	3–6 [16, 27] 3 [26] 6 [28]	2–3	1–16	1–5 [30] 2–3 [31]	1–2 and 6–7	3 and 14 [33] 3 [5]
Bath temperature (°C)	22	25	25	Not specified	30	20	25	25	20	30	22–24	23
Number of contractions	10	1	2–6	5	10	7	10	6	12	10	3	5
Time between contractions (s)	30	n/a	10	300	120	10	180	120	180^d	120	300	240^Ɛ
Total length change (%)	30	20–60^b	30^b	7.7	10	8	10	5–40^b	15–17^b	5–10	15	10
Lengthening velocity (L_o/s)	3.0	2^b	1^b	6.6–11.1 mm/s	0.5	1.0	0.5	2.0^b	1.0^b	0.5 [30] 0.5^b [31]	1 mm/s	0.5
Contraction duration (ms)	100	100–300^e	300^e	140	200	90	200	25–200^e	150–170^e	200	~ 3750^e	200
Stimulation Frequency (Hz)	120^f	~ 130^f	180^f	Not specified	150	125	175	Not specified	125	150^f	100	80 and 120 [33] 80 [5]
Isometric force loss (%)	60–70	10–50	~ 75–90	55	~ 55	> 90	80–90	60–70	38	80–95	~ 8–60^g	64

Studies are representative and do not encompass all published protocols on whole EDL muscle from mdx mice studied ex vivo
Protocols are identified based the principal investigator’s laboratory
All mdx mice had a variation of the C57BL/10 background unless indicated otherwise
ECC eccentric contraction, L_o optimal muscle length
Contraction duration is the time during the eccentric portion of the ECC
Isometric force loss is either the percent change in isometric tetanic force between the first and last contraction generated during the isometric plateau of the ECC or that from separate maximal isometric tetanic contractions before and then following the ECC protocol
^aC57BL/6 background
^bCalculated and reported based on fiber length rather than muscle length
^cPapers that include data on skeletal muscles in addition to EDL muscle
^dTime between eccentric contractions followed by 15 min between two sets of 6 ECC
^eStimulation duration calculated or estimated from publication
^fStimulation frequency of isometric tetanic contractions [stimulation frequency of ECC not specified]
^gLoss of isometric force is age-dependent

ISSN: 2044-5040