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Table 1.

Means ± standard errors of kinematic variables and electromyographic(EMG) integrated areas for each experimental animal during terrestrial and aquatic trotting, and results of one-way ANOVA testing of all variables for significant effects of environment

	Animal no. 1			Animal no. 2			Animal no. 3
	Terrestrial	Aquatic	Terrestrial	Aquatic	Terrestrial	Aquatic	Terrestrial	Aquatic
Trunk bending
Frequency (Hz)	1.7±0.1	1.9±0.2	1.1±0.0	1.0±0.1	1.6±0.1	1.4±0.1	1.2±0.1	1.3±0.0
Amplitude (deg.)	37.0±1.7	39.6±1.9	21.0±0.8	19.5±0.8	23.2±0.9	25.3±0.8	26.6±0.6	27.4±0.8
Max. extension (%)	45.4±3.1	48.2±1.0	45.5±1.8	49.2±1.0	46.5±1.6	48.9±1.5	52.7±1.4	49.0±0.7
Footfall timing (%)
LH duty factor	61.3±1.9	44.1±3.0^{^*}	57.4±3.0	65.8±2.3	64.9±2.1	55.1±2.6	71.8±2.3	56.6±2.1^{^*}
LH liftoff	62.1±1.9	46.7±2.9^{^*}	71.1±1.5	67.4±3.2	59.1±1.4	56.3±2.3	67.7±2.2	59.3±1.9^{^*}
LF duty factor	59.9±1.9	43.8±2.0^{^*}	61.4±1.7	67.5±1.6	55.6±2.7	52.0±1.3	64.9±1.5	55.6±1.3^{^*}
LF liftoff	3.0±1.5	2.7±1.6^{^*}	15.1±2.0	13.4±2.2	1.5±1.8	0.2±1.0	6.1±1.1	5.6±1.6
RF duty factor	61.3±2.2	38.6±1.5^{^*}	63.7±1.5	66.5±1.4	60.0±1.8	50.1±1.3	65.1±1.8	54.8±0.9^{^*}
RF liftoff	54.0±2.6	47.0±1.4^{^*}	66.5±1.1	65.0±1.5	51.5±1.4	51.2±0.8	54.5±1.3	53.1±0.6
RH duty factor	63.0±1.0	43.8±2.1^{^*}	58.2±1.2	59.2±1.3	63.2±6.3	57.9±1.8^{^*}	73.0±1.1	54.0±1.8^{^*}
RH liftoff	13.4±1.4	2.4±1.4^{^*}	15.5±1.9	14.6±1.8	9.8±1.5	9.6±1.6	17.5±1.4	4.1±1.5^{^*}
EMG area (mV s^–1)
Cranial site
IS			0.6±0.1	0.4±0.1	13.8±0.4	12.3±0.4	0.9±0.0	0.3±0.0^{^*}
DT	0.5±0.1	0.4±0.1	10.1±1.4	3.9±0.8^{^*}	1.9±0.2	2.0±0.7	2.3±0.2	1.4±0.1^{^*}
SL	1.1±0.2	0.8±0.1	1.2±0.1	0.6±0.1^{^*}			0.0±0.0	0.0±0.0
SM	1.0±0.2	0.8±0.1
RL			8.8±0.4	4.7±0.4^{^*}	3.2±0.2	1.1±0.1^{^*}	4.2±0.2	2.9±0.1^{^*}
OI	1.0±0.1	0.1±0.0^{^*}	8.9±0.5	4.3±0.3^{^*}	4.0±0.3	2.3±0.4^{^*}	0.1±0.0	0.0±0.0
RA	2.0±0.3	2.6±0.5	16.0±1.0	7.8±0.6^{^*}			1.1±0.1	1.6±0.1^{^*}
Caudal site
DT	12.0±0.9	13.3±1.0	6.2±0.8	2.0±0.4^{^*}	3.2±0.3	2.3±0.2	0.5±0.0	0.2±0.0^{^*}
SL	1.0±0.2	1.2±0.2	0.1±0.0	0.0±0.0	4.8±0.4	1.7±0.2^{^*}	3.0±0.2	0.9±0.0^{^*}
SM	2.6±0.6	2.5±0.4					0.8±0.1	0.3±0.0^{^*}
RL	23.6±3.8	18.0±2.7	24.1±1.0	9.8±0.8^{^*}	2.5±0.2	0.6±0.1^{^*}	1.5±0.2	0.4±0.0^{^*}
OI	0.1±0.0	0.2±0.0	4.0±0.5	1.1±0.1^{^*}	3.9±0.3	1.9±0.1^{^*}	1.1±0.1	0.2±0.0^{^*}
RA			6.8±0.4	3.1±0.4^{^*}	4.1±0.3	0.9±0.1^{^*}	4.4±0.2	2.7±0.1^{^*}

	Animal no. 1			Animal no. 2			Animal no. 3
	Terrestrial	Aquatic	Terrestrial	Aquatic	Terrestrial	Aquatic	Terrestrial	Aquatic
Trunk bending
Frequency (Hz)	1.7±0.1	1.9±0.2	1.1±0.0	1.0±0.1	1.6±0.1	1.4±0.1	1.2±0.1	1.3±0.0
Amplitude (deg.)	37.0±1.7	39.6±1.9	21.0±0.8	19.5±0.8	23.2±0.9	25.3±0.8	26.6±0.6	27.4±0.8
Max. extension (%)	45.4±3.1	48.2±1.0	45.5±1.8	49.2±1.0	46.5±1.6	48.9±1.5	52.7±1.4	49.0±0.7
Footfall timing (%)
LH duty factor	61.3±1.9	44.1±3.0^{^*}	57.4±3.0	65.8±2.3	64.9±2.1	55.1±2.6	71.8±2.3	56.6±2.1^{^*}
LH liftoff	62.1±1.9	46.7±2.9^{^*}	71.1±1.5	67.4±3.2	59.1±1.4	56.3±2.3	67.7±2.2	59.3±1.9^{^*}
LF duty factor	59.9±1.9	43.8±2.0^{^*}	61.4±1.7	67.5±1.6	55.6±2.7	52.0±1.3	64.9±1.5	55.6±1.3^{^*}
LF liftoff	3.0±1.5	2.7±1.6^{^*}	15.1±2.0	13.4±2.2	1.5±1.8	0.2±1.0	6.1±1.1	5.6±1.6
RF duty factor	61.3±2.2	38.6±1.5^{^*}	63.7±1.5	66.5±1.4	60.0±1.8	50.1±1.3	65.1±1.8	54.8±0.9^{^*}
RF liftoff	54.0±2.6	47.0±1.4^{^*}	66.5±1.1	65.0±1.5	51.5±1.4	51.2±0.8	54.5±1.3	53.1±0.6
RH duty factor	63.0±1.0	43.8±2.1^{^*}	58.2±1.2	59.2±1.3	63.2±6.3	57.9±1.8^{^*}	73.0±1.1	54.0±1.8^{^*}
RH liftoff	13.4±1.4	2.4±1.4^{^*}	15.5±1.9	14.6±1.8	9.8±1.5	9.6±1.6	17.5±1.4	4.1±1.5^{^*}
EMG area (mV s^–1)
Cranial site
IS			0.6±0.1	0.4±0.1	13.8±0.4	12.3±0.4	0.9±0.0	0.3±0.0^{^*}
DT	0.5±0.1	0.4±0.1	10.1±1.4	3.9±0.8^{^*}	1.9±0.2	2.0±0.7	2.3±0.2	1.4±0.1^{^*}
SL	1.1±0.2	0.8±0.1	1.2±0.1	0.6±0.1^{^*}			0.0±0.0	0.0±0.0
SM	1.0±0.2	0.8±0.1
RL			8.8±0.4	4.7±0.4^{^*}	3.2±0.2	1.1±0.1^{^*}	4.2±0.2	2.9±0.1^{^*}
OI	1.0±0.1	0.1±0.0^{^*}	8.9±0.5	4.3±0.3^{^*}	4.0±0.3	2.3±0.4^{^*}	0.1±0.0	0.0±0.0
RA	2.0±0.3	2.6±0.5	16.0±1.0	7.8±0.6^{^*}			1.1±0.1	1.6±0.1^{^*}
Caudal site
DT	12.0±0.9	13.3±1.0	6.2±0.8	2.0±0.4^{^*}	3.2±0.3	2.3±0.2	0.5±0.0	0.2±0.0^{^*}
SL	1.0±0.2	1.2±0.2	0.1±0.0	0.0±0.0	4.8±0.4	1.7±0.2^{^*}	3.0±0.2	0.9±0.0^{^*}
SM	2.6±0.6	2.5±0.4					0.8±0.1	0.3±0.0^{^*}
RL	23.6±3.8	18.0±2.7	24.1±1.0	9.8±0.8^{^*}	2.5±0.2	0.6±0.1^{^*}	1.5±0.2	0.4±0.0^{^*}
OI	0.1±0.0	0.2±0.0	4.0±0.5	1.1±0.1^{^*}	3.9±0.3	1.9±0.1^{^*}	1.1±0.1	0.2±0.0^{^*}
RA			6.8±0.4	3.1±0.4^{^*}	4.1±0.3	0.9±0.1^{^*}	4.4±0.2	2.7±0.1^{^*}

Maximum extension is the percentage of the locomotor cycle at which maximum extension of the ipsilateral (left) side of the trunk occurs, about midway through the locomotor cycle. Similarly, duty factor is the duration of stance phase as a percentage of the locomotor cycle, and liftoff is the time of the beginning of swing phase as a percentage of the locomotor cycle. Muscle abbreviations are provided in Fig. 1

Significant difference between terrestrial and aquatic trotting for this animal in one-way ANOVA at Bonferroni-corrected α (0.0022–0.0024)indicating significant effect of environment

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