operation (Study III)
During the deployment, the average strength and endurance training frequency of the whole subject group was 3.2 ± 1.5 training sessions per week, of which 1.5
± 0.9 sessions focused on strength and 1.7 ± 1.2 focused on endurance training (TABLE 6). The most active groups in terms of the average weekly training fre-quency were SE (3.3 ± 1.2) and C (4.0 ± 2.0).
TABLE 6 Group-wise weekly mean ± SD and range of the training frequency, volume of endurance training and volume load of strength training in the combined strength and endurance training groups and the control group during the operation. SE, 50% strength training group;
Se, 75% strength training group; Es, 25% strength training group, C, control group, LIT, low-intensity endurance training; MIT, mod-erate-intensity endurance training; HIT, high-intensity endurance training; LB, lower body; UB, upper body.
SE Se Es C
Training variables Mean±SD Range Mean±SD Range Mean±SD Range Mean±SD Range Endurance training frequency
(times) 1.5±0.6 0.6-3.1 0.7±0.6 0.0-2.0 2.2±0.8 0.8-3.5 2.2±1.7 0.0-6.5
Strength training frequency
(times) 1.6±0.8 0.4-2.8 1.7±0.5 1.1-2.4 0.8±0.4 0.0-1.4 1.8±1.4 0.0-4.7
Total training frequency (times) 3.1±1.2 1.2-5.0 2.4±0.7 1.4-3.7 3.0±1.1 0.8-4.4 4.0±2.0 1.6-8.6 LIT (<75% HRpeak) volume
(min) 62±30 30-151 50±18 30-81 78±32 36-144 55±37 20-125
MIT (75-85% HRpeak) volume
(min) 48±13 24-67 49±17 30-72 43±12 27-60 43±15 21-65
HIT (>85% HRpeak) volume
(min) 38±22 16-77 30±11 22-38 33±12 23-53 17±5 13-20
LB strength training volume
load (x1000 kg) 15.7±7.2 3.0-31.1 16.8±6.5 4.4-26.8 16.2±7.0 4.7-27.7 10.8±7.6 3.4-34.9 UB strength training volume
load (x1000 kg) 11.2±4.5 4.2- 20.8 10.0±3.0 6.2-15.0 10.1±4.2 1.8-17.3 15.0±9.3 3.8-34.5
BM increased by 1% (p < 0.05) in the SE group during the whole study period.
SMM increased by 1% (p < 0.05) in the combined group and by 2% (p < 0.05) in SE (FIGURE 8). Furthermore, FATM increased in the combined group by 3%.
Within-group changes in body composition are presented in TABLE 7. Between-group comparisons demonstrated that the decrease in SMM between PRE and POST was higher in Es than in the control group C (coef. −0.7 kg, 95% CI −1.3 to
−0.1 kg, p < 0.05).
FIGURE 8 Within-group means and standard deviations for muscle mass, 3000-m run-ning test, military simulation test and testosterone-to-cortisol ratio of the com-bined strength and endurance training groups and the control group during the operation. SE, 50% strength training group; Se, 75% strength training group; Es, 25% strength training group, C, control group. *, p < 0.05; **, p <
0.01; ***, p < 0.001.
TABLE 7 Body composition variables (mean ± SD) of the combined strength and endurance training groups and the control group at baseline (PRE), after 9 (MID) and 19 weeks (POST) and their changes within groups based on unstandardized coefficients (Coef.) and 95%
confidence intervals (CI) from linear regression models. Bold values, p < 0.05. SE, 50% strength training group; Se, 75% strength training group; Es, 25% strength training group, C, control group.
Within groups
PRE-MID PRE-POST MID-POST
n PRE MID POST Coef. (95% CI) Coef. (95% CI) Coef. (95% CI)
Body mass (kg)
SE 23 77.8±8.0 78.2±8.4 78.8±8.9 0.4 (-0.4; 1.2) 1.0 (0.01; 1.9) 0.6 (-0.02; 1.2)
Se 15 80.3±6.6 80.7±6.9 81.3±7.3 0.5 (-0.5; 1.4) 1.0 (-0.2; 2.2) 0.6 (-0.2; 1.3)
Es 18 80.6±6.6 79.8±6.0 79.9±6.2 -0.8 (-1.7; 0.1) -0.7 (-1.8; 0.4) 0.1 (-0.6; 0.8)
C 22 78.2±8.8 77.9±8.9 78.5±9.1 -0.3 (-1.1 0.5) 0.4 (-0.6; 1.4) 0.7 (0.1; 1.3)
SE, Se, Es 56 79.4±7.2 79.4±7.3 79.8±7.6 0.0 (-0.5; 0.5) 0.4 (-0.2; 1.1) 0.4 (0.05; 0.8) Muscle mass (kg)
SE 23 38.3±4.2 38.9±4.6 39.2±4.7 0.6 (0.1; 1.0) 0.9 (0.5; 1.3) 0.3 (-0.1; 0.7)
Se 15 40.9±4.1 41.4±3.8 41.3±4.4 0.5 (-0.1; 1.1) 0.3 (-0.2; 0.9) -0.1 (-0.6; 0.4)
Es 18 39.4±3.6 39.2±3.5 39.1±3.7 -0.3 (-0.8; 0.2) -0.3 (-0.8; 0.2) -0.02 (-0.5; 0.4)
C 22 38.7±4.5 38.9±4.6 39.1±4.7 0.2 (-0.3; 0.7) 0.4 (-0.03; 0.8) 0.2 (-0.2; 0.6)
SE, Se, Es 56 39.4±4.0 39.6±4.1 39.7±4.4 0.2 (-0.03; 0.6) 0.4 (0.1; 0.7) 0.1 (-0.2; 0.4) Fat mass (kg)
SE 23 10.9±3.9 10.3±3.8 10.5±3.1 -0.6 (-1.2; 0.1) -0.3 (-1.0; 0.3) 0.2 (-0.3; 0.8)
Se 15 9.2±3.1 8.8±3.1 9.6±3.0 -0.6 (-1.4; 0.3) 0.2 (-0.7; 1.0) 0.6 (-0.1; 1.3)
Es 18 11.9±4.0 11.6±3.9 11.8±3.5 -0.1 (-0.9; 0.7) 0.1 (-0.6; 0.9) 0.3 (-0.3; 1.0)
C 22 10.6±4.7 10.1±4.4 10.5±4.9 -0.5 (-1.2; 0.2) -0.1 (-0.8; 0.6) 0.4 (-0.2; 1.0)
SE, Se, Es 56 10.7±3.8 10.3±3.7 10.7±3.3 -0.4 (-0.8; 0.02) -0.05 (-0.5; 0.4) 0.4 (0.02; 0.7)
No within-group changes were observed in 3000-m time but all groups improved their MST time between every measurement point (FIGURE 8). No differences in the changes in 3000-m or MST times were observed between the intervention groups and C. SLJ decreased by 2% (p < 0.05) in C during the study.
Significant PRE-POST increases in MVClower occurred in all intervention groups (TABLE 8). Between-group analysis (reference group C) showed a higher PRE-POST increase in the combined intervention group (coef. 415 N, 95% CI 97 to 733 N, p < 0.05) and Se (coef. 611 N, 95% CI 181 to 1040 N, p < 0.05). Compared to C, the increase in MVClower was significantly higher between PRE and MID in Se (coef. 632 N, 95% CI 232 to 1031 N, p < 0.05), while in Es the respective change was higher between MID and POST (coef. 353 N, 95% CI 10 to 696 N, p < 0.05).
MVCupper increased from PRE to MID in the combined intervention group by 2%
(p < 0.05), whereas between MID and POST, a decrease of 3% (p < 0.05) was ob-served in C (TABLE 8). All groups showed improvements in muscular endurance test results throughout the study (TABLE 9).
TES increased by 16% (p < 0.05) in Es and by 10% (p < 0.05) in the combined intervention group during the study. In the same time period, COR decreased by 9% (p < 0.05) in the combined intervention group. The TES/COR ratio increased during the different phases of the study in the combined intervention group, Se and SE, but not in C or Es (FIGURE 8). No differences were detected in the above-mentioned changes between the intervention groups and the C group. No within- or between-group changes were observed in IGF-1. The TES/SHBG ratio increased between PRE and POST in all groups, while between-group compari-sons showed a PRE-MID decrease in Se compared to C (coef. −0.12 nmol· L-1, 95%
CI −0.24 to −0.01 nmol· L-1, p < 0.05), but between MID and POST the respective change was positive (coef. 0.23 nmol· L-1, 95% CI 0.05 to 0.42 nmol· L-1, p < 0.05).
Within-group changes in serum anabolic and catabolic biomarkers are presented in TABLE 10.
TABLE 8 Muscular strength and power variables (mean ± SD) of the combined strength and endurance training groups and the control group at baseline (PRE), after 9 (MID) and 19 weeks (POST) and their changes within groups based on unstandardized coefficients (Coef.) and 95% confidence intervals (CI) from linear regression models. Bold values, p < 0.05. SE, 50% strength training group; Se, 75% strength training group; Es, 25% strength training group, C, control group.
Within groups
PRE-MID PRE-POST MID-POST
n PRE MID POST Coef. (95% CI) Coef. (95% CI) Coef. (95% CI)
Maximal voluntary force of the lower extremities (N)
SE 19 4216±797 4547±964 4651±1036 331 (83; 580) 435 (168; 702) 97 (-130; 324)
Se 12 4168±1110 4997±1598 4908±1448 833 (520; 1146) 740 (404; 1077) -34 (-323; 255)
Es 15 4337±735 4609±828 4863±982 264 (-17; 544) 526 (225; 827) 256 (-0.1; 511)
C 19 4196±1081 4395±1191 4325±1013 201 (-47; 450) 129 (-138; 397) -98 (-326; 131)
SE, Se, Es 46 4243±853 4684±1116 4787±1121 440 (272; 608) 544 (372; 716) 115 (-31; 262) Maximal voluntary force of the upper extremities (N)
SE 20 1150±261 1177±263 1167±263 27 (-9; 64) 18 (-23; 60) -9 (-42; 25)
Se 11 1121±204 1142±213 1163±210 20 (-29 69) 40 (-16; 95) 18 (-27; 64)
Es 15 1199±185 1228±172 1204±172 33(-9; 74) 12 (-36; 59) -19 (-58; 20)
C 19 1104±253 1137±250 1102±232 30 (-7; 68) -6 (-48; 36) -37 (-72; -3)
SE, Se, Es 46 1159±223 1185±223 1178±220 27 (4; 51) 21 (-6; 48) -6 (-28; 16)
Standing long jump (cm)
SE 18 234±26 237±27 231±28 2.8 (-0.9; 6.6) -3.2 (-7.8; 1.4) -6.0 (-10.0; -2.1)
Se 12 238±21 238±20 236±17 -0.1 (-4.7; 4.5) 2.1 (-7.8; 3.5) -2.0 (-6.9; 2.8)
Es 15 238±20 241±22 238±22 3.1 (-1.0; 7.3) 0.9 (-4.1; 6.0) -2.0 (-6.4; 2.3)
C 19 236±25 235±28 230±29 -1.3 (-4.9; 2.4) -5.6 (-10.0; -1.1) -4.4 (-8.3; -0.6)
SE, Se, Es 45 236±22 238±23 235±25 2.2 (-0.2; 4.5) -1.5 (-4.4; 1.4) -3.6 (-6.1; -1.1)
TABLE 9 Muscular endurance variables (mean ± SD) of the combined strength and endurance training groups and the control group at baseline (PRE), after 9 (MID) and 19 weeks (POST) and their changes within groups based on unstandardized coefficients (Coef.) and 95%
confidence intervals (CI) from linear regression models. Bold values, p < 0.05. SE, 50% strength training group; Se, 75% strength training group; Es, 25% strength training group, C, control group.
Within groups
PRE-MID PRE-POST MID-POST
n PRE MID POST Coef. (95% CI) Coef. (95% CI) Coef. (95% CI)
Sit-ups (repetitions in one minute)
SE 20 45±10 47±9 48±8 1.8 (0.3 to 3.4) 2.8 (0.8 to 4.7) 0.9 (-0.6 to 2.4)
Se 12 46±7 47±8 49±9 0.6 (-1.4 to 2.7) 2.7 (0.2 to 5.3) 2.1 (0.1 to 4.0)
Es 15 48±9 50±8 50±9 2.6 (0.8 to 4.4) 2.5 (0.2 to 4.8) -0.0 (-1.8 to 1.8)
C 19 46±10 46±10 48±10 -0.1 (-1.7 to 1.5) 1.8 (-0.3 to 3.8) 1.8 (0.3 to 3.4)
SE, Se, Es 47 46±9 48±8 49±9 1.8 (0.8 to 2.8) 2.7 (1.4 to 3.9) 0.9 (-0.1 to 1.9)
Push-ups (repetitions in one minute)
SE 20 40±12 41±10 44±13 0.7 (-2.0 to 3.5) 4.3 (0.7 to 8.0) 3.6 (0.7 to 6.5)
Se 11 37±11 41±11 46±11 2.7 (-1.0 to 6.4) 8.7 (3.7 to 13.7) 5.9 (2.0 to 9.8)
Es 15 44±14 46±15 50±13 2.1 (-1.1 to 5.3) 6.7 (2.4 to 11.0) 4.8 (1.4 to 8.2)
C 19 39±13 39±12 45±16 -0.2 (-3.0 to 2.6) 5.7 (2.0 to 9.5) 5.9 (2.9 to 8.8)
SE, Se, Es 46 41±13 42±12 47±13 1.6 (-0.2 to 3.4) 6.2 (3.7 to 8.6) 4.5 (2.6 to 6.4) Pull-ups (repetition maximum)
SE 20 9±6 11±5 12±6 1.8 (0.7 to 2.8) 2.7 (1.4 to 4.0) 0.9 (-0.0 to 1.9)
Se 12 9±4 10±6 12±6 0.8 (-0.5 to 2.2) 2.9 (1.1 to 4.6) 2.0 (0.7 to 3.3)
Es 15 12±5 13±6 15±6 1.5 (0.3 to 2.7) 3.6 (2.0 to 5.1) 2.1 (0.9 to 3.2)
C 19 9±5 11±6 12±6 1.8 (0.8 to 2.9) 2.8 (1.4 to 4.2) 0.9 (-0.1 to 2.0)
SE, Se, Es 47 10±5 11±6 13±6 1.4 (0.8 to 2.1) 3.0 (2.2 to 3.9) 1.6 (0.9 to 2.2)
TABLE 10 Serum anabolic and catabolic biomarkers (mean ± SD) of the combined strength and endurance training groups and the control group at baseline (PRE), after 9 (MID) and 19 weeks (POST) and their changes within groups based on unstandardized coefficients (Coef.) and 95% confidence intervals (CI) from linear regression models. Bold values, p < 0.05. SE, 50% strength training group; Se, 75% strength training group; Es, 25% strength training group, C, control group.
Within groups
PRE-MID PRE-POST MID-POST
n PRE MID POST Coef. (95% CI) Coef. (95% CI) Coef. (95% CI)
Testosterone (nmol· L-1)
SE 19 15.4±3.9 16.4±3.7 16.7±2.9 0.7 (-0.8 to 2.3) 0.9 (-0.5 to 2.3) -0.3 (-1.8 to 1.2) Se 11 15.4±2.5 15.9±2.4 17.4±2.7 0.2 (-1.8 to 2.2) 1.7 (-0.2 to 3.6) 0.7 (-1.3 to 2.7) Es 12 16.9±7.1 18.0±4.9 19.0±5.1 1.5 (-0.4 to 3.5) 2.7 (0.9 to 4.5) 1.5 (-0.4 to 3.4) C 16 16.3±4.5 18.6±4.6 17.2±3.4 2.4 (0.8 to 4.1) 1.1 (-0.5 to 2.7) -0.5 (-2.2 to 1.1) SE, Se, Es 42 15.9±4.7 16.7±3.8 17.6±3.6 0.8 (-0.2 to 1.8) 1.6 (0.6 to 2.6) 0.5 (-0.5 to 1.5) Cortisol (nmol· L-1)
SE 19 431±74 421±127 385±130 -7 (-61 to 47) -44 (-98 to 9) -55 (-113 to 2)
Se 11 430±97 459±95 402±156 31 (-40 to 102) -27 (-98 to 43) -48 (-123 to 27)
Es 12 455±114 453±132 409±118 20 (-49 to 88) -33 (-101 to 35) -39 (-111 to 33)
C 16 401±118 465±109 412±105 42 (-17 to 102) -2 (-61 to 57) -39 (-102 to 23)
SE, Se, Es 42 438±91 440±120 396±131 10 (-26 to 47) -37 (-72 to -1) -49 (-87 to -11) Sex-hormone binding globulin (nmol· L-1)
SE 19 31.0±10.2 25.7±8.3 23.6±10.4 -6.0 (-9.3 to -2.6) -7.9 (-11.7 to -4.0) -2.8 (-6.7 to 1.1) Se 11 32.4±11.8 35.6±8.6 22.5±8.9 3.2 (-1.2 to 7.7) -9.9 (-14.9 to -4.8) -12.5 (-17.5 to -7.5) Es 12 34.7±14.9 32.8±11.9 30.9±16.6 -0.8 (-5.0 to 3.5) -3.0 (-7.8 to 1.9) -1.6 (-6.3 to 3.1) C 15 32.2±11.9 32.4±10.1 27.2±9.8 0.1 (-3.7 to 3.9) -5.0 (-9.3 to -0.7) -5.0 (-9.2 to -0.8) SE, Se, Es 42 32.4±11.9 30.3±10.3 25.4±12.4 -2.1 (-4.5 to 0.4) -7.0 (-9.6 to -4.4) -5.0 (-7.8 to -2.3)
Multiple linear regression with backward elimination showed that relative changes in strength training frequency, MST time and the TES/SHBG ratio ex-plained 32% of the variance in the change in SMM (R2adj = 0.317). Relative changes in LB strength training volume load and in 3000-m time were correlated with relative change in FATM (R2adj = 0.514). Finally, the relative change in 3000-m time was associated with respective changes in BMI, MST time, pull-up repeti-tions and PRE-3000-m time, which together explained 68% of the variance in 3000-m time (R2adj = 0.675).
5.4 Endurance-related training adaptations during a military