Effects of free leucine supplementation and resistance training on muscle strength and functional status in older adults: a randomized controlled trial

Figures & data

Figure 1 Flowchart of study groups at different time points.

Note: Subject dropout is reported as “lost”.

Table 1 Baseline characteristics of participants

	Control (n=12)	Leucine (n=12)
Age (years)	84±4	85±8
Dynamometry (kg)	27.5±15.7	29.9±25.3
Standing balance (seconds)	1.7±1.7	4.4±7.5
4 m walk (seconds)	5.0±1.2	5.8±1.8
Chair stands (seconds)	14.9±3.9	20.8±8.2
Timed up and go (seconds)	16.9±6.1	18.2±5.5
Barthel Index	90±12	87±15
Weight (kg)	62.9±15.4	64.6±9.4
BMI (kg/m^2)	26.0±5.2	26.6±4.4
Triceps skinfold (mm)	20.3±8.3	21.7±6.2
MUAMA (mm)	21.6±3.3	20.8±2.4
Calf circumference (mm)	33.4±4.2	33.3±2.6
Waist circumference (cm)	96.3±15	97.5±8
MNA	23.5±5	24.0±3
Barthel Index	90.4±12	87.1±15
GDS	5.0±3.5	5.4±2.8
Energy requirements (kcal)	1,489±328	1,560±300
Protein requirements (g)	64±16	67±9
Energy intake (kcal)	1,574±200	1,694±257
Protein intake (g)	76±12	81±6

Note: All values are means ± standard deviations.

Abbreviations: BMI, body mass index; GDS, Geriatric Depression Scale; MNA, Mini Nutritional Assessment; MUAMA, mid-upper arm muscle area.

Table 2 Muscle strength and functional status of participants

	Baseline	Adjusted baseline difference at 4 weeks	Adjusted baseline difference at 12 weeks
Leg strength (kg)
Leucine	29.942 (6.226) [17.227, 42.657]	9.971 (1.488) [6.605, 13.338]	12.482 (1.824) [8.355, 16.609]
Control	27.508 (6.226) [14.793, 40.223]	5.032 (1.490) [1.663, 8.402]	6.007 (2.307) [0.789, 11.226]
Differences	–	4.939 (2.107) [0.172, 9.705], P=0.044	6.475 (2.951) [−0.200, 13.149], P=0.056
Effect size*	–	0.677	0.633
Standing balance (seconds)
Leucine	4.358 (1.731) [0.822, 7.895]	1.698 (0.881) [−0.294, 3.691]	1.698 (0.900) [−0.338, 3.733]
Control	1.717 (1.731) [−1.820, 5.253]	0.610 (0.887) [−1.396, 2.617]	2.428 (0.939) [0.304, 4.551]
Differences	–	1.088 (1.269) [−1.782, 3.958], P=0.414	−0.730 (1.319) [−3.714, 2.254], P=0.594
Effect size*	–	0.247	−0.160
4 m walk (seconds)
Leucine	5.775 (0.420) [4.918, 6.632]	−0.621 (0.268) [−1.227, −0.014]	−0.995 (0.289) [−1.649, −0.340]
Control	4.950 (0.420) [4.093, 5.807]	−0.240 (0.267) [−0.844, 0.363]	−0.315 (0.326) [−1.052, 0.422]
Differences	–	−0.380 (0.385) [−1.252, 0.491], P=0.349	−0.680 (0.441) [−1.676, 0.317], P=0.157
Effect size*	–	−0.285	−0.445
Chair stands (seconds)
Leucine	20.845 (1.632) [17.491, 24.199]	−3.578 (0.775) [−5.331, −1.825]	−5.150 (1.010) [−7.434, −2.866]
Control	14.922 (1.804) [11.214, 18.630]	−2.830 (0.899) [−4.864, −0.795]	−1.924 (1.284) [−4.830, 0.981]
Differences	–	−0.748 (1.216) [−3.499, 2.002], P=0.554	−3.226 (1.669) [−7.001, 0.550], P=0.085
Effect size*	–	−0.178	−0.558
Timed up and go (seconds)
Leucine	18.158 (1.620) [14.849, 21.467]	−3.139 (0.709) [−4.742, −1.535]	−3.541 (0.738) [−5.210, −1.872]
Control	16.875 (1.620) [13.566, 20.184]	−1.251 (0.709) [−2.856, 0.353]	−0.796 (0.788) [−2.578, 0.987]
Differences	–	−1.887 (1.006) [−4.163, 0.388], P=0.093	−2.745 (1.083) [−5.195, −0.296], P=0.032
Effect size*	–	−0.542	−0.732

Notes: Values are least square means, (standard error of the mean), and [95% confidence interval].

* The effect size is the treatment effect difference divided by its standard deviation.

Table 3 Body composition, nutritional status according to MNA score, and dietary intake

	Baseline	Adjusted baseline difference at 4 weeks	Adjusted baseline difference at 12 weeks
Weight (kg)
Leucine	64.625 (3.692) [56.987, 72.263]	0.634 (0.525) [−0.459, 1.726]	0.571 (0.595) [−0.666, 1.808]
Control	62.875 (3.692) [55.237, 70.513]	−0.226 (0.528) [−1.324, 0.872]	−0.228 (0.630) [−1.538, 1.083]
Differences	–	0.859 (0.745) [−0.690, 2.408], P=0.262	0.799 (0.866) [−1.003, 2.600], P=0.367
BMI (kg/m^2)
Leucine	26.600 (1.395) [23.714, 29.486]	0.317 (0.205) [−0.110, 0.744]	0.377 (0.228) [−0.098, 0.851]
Control	26.033 (1.395) [23.147, 28.920]	−0.060 (0.206) [−0.488, 0.369]	−0.072 (0.238) [−0.568, 0.424]
Differences	–	0.376 (0.291) [−0.229, 0.981], P=0.210	0.449 (0.330) [−0.238, 1.135], P=0.188
Triceps skin fold (mm)
Leucine	21.717 (2.117) [17.338, 26.095]	−0.016 (0.116) [−0.258, 0.225]	−0.022 (0.345) [−0.739, 0.695]
Control	20.325 (2.117) [15.946, 24.704]	0.170 (0.116) [−0.071, 0.411]	−0.213 (0.394) [−1.032, 0.605]
Differences	–	−0.186 (0.164) [−0.528, 0.155], P=0.269	0.191 (0.523) [−0.896, 1.279], P=0.718
MUAMA (mm)
Leucine	20.767 (0.844) [19.021, 22.513]	−0.016 (0.076) [−0.175, 0.143]	0.396 (0.174) [0.033, 0.758]
Control	21.583 (0.844) [19.837, 23.329]	−0.083 (0.075) [−0.240, 0.074]	−0.486 (0.185) [−0.871, −0.101]
Differences	–	0.067 (0.107) [−0.156, 0.290], P=0.541	0.882 (0.252) [0.358, 1.407], P=0.002
Calf circumference (mm)
Leucine	33.325 (1.011) [31.233, 35.417]	0.197 (0.108) [−0.029, 0.422]	0.203 (0.102) [−0.009, 0.415]
Control	33.433 (1.011) [31.341, 35.525]	0.140 (0.108) [−0.085, 0.366]	−0.094 (0.118) [−0.340, 0.152]
Differences	–	0.057 (0.153) [−0.262, 0.375], P=0.716	0.297 (0.156) [−0.028, 0.622], P=0.071
Waist circumference (cm)
Leucine	97.500 (3.521) [90.215, 104.78]	1.096 (0.876) [−0.726, 2.918]	1.122 (1.484) [−1.964, 4.207]
Control	96.333 (3.521) [89.049, 103.62]	0.562 (0.877) [−1.261, 2.385]	0.293 (1.736) [−3.318, 3.904]
Differences	–	0.534 (1.240) [−2.045, 3.113], P=0.671	0.828 (2.284) [−3.921, 5.578], P=0.721
MNA
Leucine	24.000 (1.126) [21.670, 26.330]	1.099 (0.429) [0.207, 1.991]	1.455 (0.974) [−0.570, 3.481]
Control	23.500 (1.126) [21.170, 25.830]	0.461 (0.431) [−0.434, 1.357]	1.053 (1.243) [−1.532, 3.637]
Differences	–	0.638 (0.608) [−0.627, 1.902], P=0.306	0.403 (1.579) [−2.882, 3.687], P=0.801
Energy intake (kcal)
Leucine	1,693.6 (66.473) [1,556.1, 1,831.1]	32.866 (36.369) [−42.77, 108.50]	−2.872 (49.357) [−105.5, 99.771]
Control	1,574.0 (66.473) [1,436.5, 1,711.5]	87.443 (36.701) [11.119, 163.77]	94.155 (64.242) [−39.44, 227.75]
Differences	–	−54.58 (52.274) [−163.3, 54.133], P=0.308	−97.03 (83.650) [−271.0, 76.932], P=0.259
Protein intake (g)
Leucine	81.250 (2.537) [76.069, 86.431]	4.404 (2.247) [−0.678, 9.486]	−2.905 (2.694) [−9.000, 3.189]
Control	76.000 (2.537) [70.819, 81.181]	10.123 (2.255) [5.022, 15.223]	1.056 (3.353) [−6.528, 8.641]
Differences	–	−5.718 (3.244) [−13.06, 1.621], P=0.112	−3.962 (4.415) [−13.95, 6.026], P=0.393

Notes: Values are least square means, (standard error of the mean), and [95% confidence interval].

Abbreviations: BMI, body mass index; MNA, Mini Nutritional Assessment; MUAMA, mid-upper arm muscle area.

Figure 2 Health-related quality of life according to the SF-36 questionnaire.

Notes: Health-related quality of life intra-group scores for both groups of study (A, B). The PF domain shows an increase >25% in the leucine group after the intervention, that increase in the control group was 16%.
Abbreviations: BP, bodily pain; GH, general health; MH, mental health; PF, physical function; RE, role emotional; RP, role physical; SF, social function; SF-36, 36-Item Short-Form Health Survey; VT, vitality.