Acute effects of an isometric neck warm-up programme on neck performance characteristics and ultrasound-based morphology

Figures & data

Figure 1. A Crossover research design. Top and bottom figure is study arm #1 and arm #2, respectively.

Table 1. Demographics.

	Study Arm #1 Visit 1 (n = 26: 13f/13m)	Study Arm #1 Visit 2 (n = 15: 10f/5m)	Study Arm #2 (n = 24: 13f/11m)
Age, years	24.2 ± 1.7	24.5 ± 2.1	24.6 ± 3.6
Height, cm	171.8 ± 8.2	168.1 ± 7.4	172.4 ± 9.2
Weight, kg	72.3 ± 11.2	70.6 ± 11.3	70.7 ± 11.8

Figure 2. Neck force raw data before (pre) and after (post) neck warm-up. Higher rate of force development was observed while the peak force was mostly unchanged. Visual-motor reaction time was calculated as the time for the force >5 Newtons.

Figure 3. Force steadiness trials with visual feedback trial (force is flat and steady around 15 Newtons) and without visual feedback (force is overshot and gradual declines). force replication sense error was calculated as the average force output difference between two conditions during the Middle 8 s.

Figure 4. Ultrasound images: A. the sternocleidomastoid thickness and the longus colli cross-sectional area (CSA); B. the sternocleidomastoid shear wave elastography (SWE); C. the upper trapezius thickness and shear wave elastography; and D. the cervical extensors (EXT) thickness.

Table 2. Peak force (PF), visual-motor reaction time (VMRT), and rate of force development (RFD) values in the directions of flexion (flex), extension (ext), and right/left lateral flexions (right and left) before (PRE) and after (POST) neck warm-up and sham warm-up.

	Neck Warm-up		Time	Sham		Time	Interaction
Study Arm #1	PRE	POST	p	PRE	POST	p	p
Flex PF, N	131.6 ± 54.2 (59.1, 290.4)	131.1 ± 51.7 (54.9, 263.8)	0.880	119.1 ± 32.8 (63.0, 173.7)	118.7 ± 29.1 (66.3, 155.8)	0.940	0.976
Flex VMRT, ms	472.3 ± 85.6 (337.0, 601.0)	471.3 ± 102.8 (301.0, 684.0)	0.940	529.9 ± 49.4 (447.0, 626.0)	531.1 ± 69.3 (452.0, 676.0)	0.948	0.921
Flex RFD50, N/s	525.5 ± 427.6 (89.1, 2092.8)	602.1 ± 338.6 (111.5, 1614.1)	0.160	445.9 ± 197.9 (211.8, 840.8)	469.9 ± 189.1 (249.7, 974.8)	0.475	0.483
Flex RFD100, N/s	600.3 ± 391.1 (81.9, 1961.0)	685.7 ± 341.2 (142.8, 1631.9)	0.022*	520.4 ± 210.2 (208.6, 873.1)	590.3 ± 209.9 (329.1, 933.5)	0.052	0.769
Flex RFD150, N/s	517.7 ± 309.4 (78.6, 1674.1)	547.2 ± 257.9 (169.5, 1314.2)	0.227	469.6 ± 166.8 (204.7, 790.1)	462.5 ± 41.9 (302.3, 813.3)	0.500	0.913
Flex RFD200, N/s	418.7 ± 211.7 (89.7, 1186.4)	437.8 ± 193.3 (167.4, 1037.0)	0.214	377.4 ± 122.5 (183.4, 552.3)	406.9 ± 127.7 (237.4, 645.8)	0.208	0.692
Ext PF, N	207.8 ± 70.3 (91.3, 375.4)	222.9 ± 76.4 (74.8, 385.0)	0.060	194.7 ± 66.1 (79.2, 346.8)	192.6 ± 69.2 (59.1, 359.5)	0.540	0.048*
Ext VMRT, ms	465.9 ± 83.8 (320.7, 629.0)	450.8 ± 76.2 (322.3, 596.0)	0.243	508.3 ± 51.0 (438.0, 579.0)	510.8 ± 63.6 (423.0, 665.0)	0.859	0.376
Ext RFD50, N/s	626.8 ± 344.4 (108.5, 1900.5)	775.2 ± 468.5 (210.0, 2590.8)	0.003*	592.9 ± 258.6 (247.1, 1022.8)	569.5 ± 324.4 (227.6, 1539.7)	0.628	0.019*
Ext RFD100, N/s	871.4 ± 434.0 (132.7, 2135.2)	1122.7 ± 516.1 (250.3, 2486.3)	<0.001*	952.1 ± 469.3 (298.7, 1844.0)	961.5 ± 480.0 (220.2, 1935.7)	0.876	0.011*
Ext RFD150, N/s	810.7 ± 404.2 (140.2, 2034.6)	988.5 ± 464.8 (266.6, 2201.8)	0.001*	841.4 ± 382.9 (318.5, 1540.2)	818.0 ± 367.8 (226.8, 1639.4)	0.556	0.007*
Ext RFD200, N/s	683.6 ± 319.6 (145.8, 1703.7)	820.6 ± 377.0 (245.4, 1806.2)	0.001*	716.9 ± 272.9 (294.1, 1229.5)	691.1 ± 267.2 (227.4, 1340.2)	0.418	0.003*
Right PF, N	146.2 ± 59.1 (66.2, 330.6)	148.2 ± 51.3 (62.8, 294.1)	0.617	142.8 ± 28.7 (81.6, 180.8)	138.3 ± 36.3 (55.5, 191.5)	0.500	0.399
Right VMRT, ms	426.1 ± 64.2 (318.0, 587.0)	430.7 ± 88.0 (318.3, 703.0)	0.734	489.2 ± 44.7 (410.0, 558.0)	469.5 ± 68.7 (391.0, 675.0)	0.419	0.339
Right RFD50, N/s	549.8 ± 232.1 (185.2, 1216.3)	598.9 ± 281.5 (159.2, 1490.8)	0.032*	522.9 ± 229.8 (187.3, 1226.0)	504.9 ± 229.8 (262.8, 1169.7)	0.608	0.091
Right RFD100, N/s	711.0 ± 328.4 (203.8, 1489.7)	789.6 ± 371.8 (195.3, 1706.9)	0.005*	709.7 ± 274.4 (231.9, 1173.6)	327.4 ± 84.5 (297.4, 1414.5)	0.745	0.066
Right RFD150, N/s	618.5 ± 268.8 (218.4, 1337.7)	674.7 ± 305.6 (217.2, 1500.6)	0.004*	632.5 ± 195.1 (280.0, 950.5)	634.7 ± 220.4 (274.0, 1157.6)	0.945	0.115
Right RFD200, N/s	475.5 ± 184.0 (213.3, 919.5)	513.8 ± 218.4 (236.9, 1082.0)	0.009*	480.3 ± 121.1 (321.5, 671.9)	478.0 ± 134.3 (223.9, 714.7)	0.889	0.070
Left PF, N	143.9 ± 53.3 (67.3, 264.1)	152.1 ± 51.2 (47.8, 265.8)	0.037*	145.3 ± 32.9 (66.0, 207.0)	137.1 ± 31.7 (65.4, 192.4)	0.066	0.008*
Left MVRT, ms	442.2 ± 92.4 (307.0, 714.0)	430.4 ± 94.4 (303.0, 721.0)	0.445	489.6 ± 37.8 (432.0, 537.0)	490.1 ± 47.9 (395.0, 590.0)	0.972	0.586
Left RFD50, N/s	595.2 ± 282.4 (178.0, 1287.8)	626.9 ± 276.7 (215.2, 1232.2)	0.331	553.1 ± 328.0 (258.0, 1553.1)	556.5 ± 266.3 (338.8, 1323.2)	0.927	0.576
Left RFD100, N/s	769.7 ± 406.3 (178.5, 1837.7)	834.6 ± 376.5 (242.0, 1512.9)	0.135	724.2 ± 348.0 (266.3, 1400.3)	769.5 ± 384.8 (365.8, 1534.7)	0.418	0.777
Left RFD150, N/s	653.9 ± 292.6 (194.1, 1395.5)	724.7 ± 300.7 (216.3, 1296.4)	0.014*	649.1 ± 217.0 (271.3, 946.8)	656.5 ± 224.7 (348.1, 1090.0)	0.771	0.121
Left RFD200, N/s	475.7 ± 181.8 (167.4, 856.6)	532.7 ± 198.8 (190.7, 913.2)	0.005*	480.2 ± 129.7 (236.6, 682.5)	473.0 ± 121.0 (278.7, 673.7)	0.610	0.008*

Under the PRE and POST column, means, standard deviations, minimums/maximums (in parentheses) are shown. The column after PRE and POST is representing p-values comparing the pre- vs. post-values within each intervention (neck warm-up or sham), based on paired t-tests. The last column represents p-values based on the interaction (differences in the pattern of pre-/post-values) between two interventions based on two-way ANOVA analysis.

* represent significant differences (p < 0.05).

Table 3. Cervical flexion muscular force output and steadiness (coefficient of variation: CoV) with the visual feedback condition (VF) and without visual feedback condition (NoVF), absolute force replication error between force out under VF and NoVF conditions, cervical range-of-motion (ROM) before (PRE) and after (POST) neck warm-up with isometric contractions and sham warm-up.

	Neck Warm-up		Time	Sham		Time	Interaction
Study Arm #1	PRE	POST	p	PRE	POST	p	p
Force Output VF, N	14.9 ± 2.0 (13.6, 24.3)	15.0 ± 1.9 (14.1, 24.4)	0.217	14.6 ± 0.4 (14.1, 15.4)	14.8 ± 0.6 (14.3, 16.7)	0.159	0.672
CoV VF, %	4.7 ± 1.7 (2.3, 10.3)	4.3 ± 1.2 (2.1, 6.4)	0.138	4.2 ± 0.5 (3.0, 4.8)	3.9 ± 0.9 (2.3, 5.1)	0.315	0.663
Force Output NoVF, N	15.2 ± 4.7 (6.5, 28.3)	17.9 ± 7.2 (9.5, 42.5)	0.011*	14.4 ± 4.0 (8.0, 21.1)	15.1 ± 3.5 (9.8, 23.3)	0.379	0.171
CoV NoVF, %	6.2 ± 2.0 (3.5, 10.7)	6.9 ± 2.1 (3.4, 12.0)	0.079	8.4 ± 3.1 (2.7, 13.0)	7.8 ± 3.3 (2.5, 14.5)	0.597	0.248
Fore Replication Error, N	3.6 ± 3.2 (0.0, 13.7)	5.1 ± 6.1 (0.0, 27.6)	0.115	2.9 ± 2.1 (0.0, 6.3)	2.3 ± 1.9 (0.3, 6.6)	0.347	0.132
Flex ROM, °	57.1 ± 10.9 (25.0, 70.0)	59.2 ± 9.6 (39.0, 72.6)	0.111	56.1 ± 8.5 (43.0, 73.0)	60.4 ± 9.3 (39.0, 74.0)	0.036*	0.329
Ext ROM, °	76.9 ± 10.1 (61.3, 100.0)	78.5 ± 10.0 (59.0, 103.0)	0.194	79.5 ± 11.1 (63.0, 106.0)	79.3 ± 10.8 (62.0, 103.0)	0.862	0.344
Lat. Right ROM, °	43.4 ± 7.5 (31.0, 54.0)	45.4 ± 7.6 (33.0, 60.0)	0.026*	44.9 ± 7.7 (28.0, 56.0)	47.9 ± 6.8 (32.0, 60.0)	0.014*	0.425
Lat. Left ROM, °	44.8 ± 8.3 (31.6, 61.0)	46.7 ± 8.1 (33.0, 60.0)	0.003*	48.1 ± 7.3 (35.0, 63.0)	50.0 ± 6.9 (39.0, 61.0)	0.209	0.964
Rot. Right ROM, °	69.0 ± 7.9 (56.7, 88.0)	70.1 ± 6.4 (60.0, 82.0)	0.277	71.3 ± 8.3 (60.0, 86.0)	72.7 ± 7.6 (55.0, 82.0)	0.309	0.889
Rot. Left ROM, °	70.5 ± 6.7 (60.0, 88.0)	70.8 ± 6.6 (59.0, 90.0)	0.810	73.8 ± 7.0 (64.0, 90.0)	74.7 ± 7.0 (65.0, 90.0)	0.423	0.697

Under the PRE and POST column, means, standard deviations, minimums/maximums (in parentheses) are shown. The column after PRE and POST is representing p-values comparing the pre- vs. post-values within each intervention (neck warm-up or sham), based on paired t-tests. The last column represents p-values based on the interaction (differences in the pattern of pre-/post-values) between two interventions based on two-way ANOVA analysis.

* represent significant differences.

Table 4. Ultrasound-based neck muscle morphological properties: cross-sectional area (CSA), thickness, and/or shear wave elastography (SWE) of the longus collis (LC), sternocleidomastoid (SCM), upper trapezius (up), and the cervical extensors (EXT) at sham (20-minute rest), before (PRE) and after (POST) the maximum voluntary isometric contractions.

				ANOVA
Study Arm #2	Sham	PRE	POST	p
LC CSA, cm²	0.75 ± 0.25 (0.39, 1.36)	0.77 ± 0.29 (0.37, 1.52)	0.88 ± 0.36* (0.44, 1.85)	0.016*
SCM Thickness, cm	0.75 ± 0.18 (0.45, 1.19)	0.74 ± 0.20 (0.44, 1.11)	0.83 ± 0.19* (0.52, 1.25)	0.004*
SCM SWE, kPa	32.2 ± 6.3 (17.6, 43.9)	30.8 ± 8.9 (13.1, 46.9)	33.1 ± 11.6 (18.6, 74.2)	0.560
UT Thickness, cm	1.23 ± 0.28 (0.51, 1.90)	1.12 ± 0.34 (0.60, 1.92)	1.17 ± 0.34 (0.47, 2.01)	0.653
UT SWE, kPa	25.6 ± 11.1 (13.3, 57.0)	25.4 ± 8.3 (11.7, 41.0)	29.4 ± 12.2 (13.9, 64.7)	0.094
EXT Thickness, cm	1.95 ± 0.29 (1.09, 2.40)	2.0 ± 0.34 (1.19, 2.60)	2.1 ± 0.37 (1.44, 3.18)	0.151

Under the PRE and POST column, means, standard deviations, minimums/maximums (in parentheses) are shown. The last column represents p-values based on differences among three time points (sham, PRE, and POST) based on one-way ANOVA analysis.

* POST values were significantly larger than sham or PRE values.

Data availability statement

Data are available upon reasonable request.