Creatine and HIV+ Patients Table 2. Muscle Strength and Energetics at Baseline and Changes on Study. 21 (8 to 5) 9 (23 to 22) 213 (229 to 3) 212 (228 to 4) 3 (25 to 11) 0 (25 to 4) 0 (24 to 4) 1 (22 to 4) 0 (21 to 2) 228 (276 to 9) Changes wk 0 Changes wk Differences between groups Mean Baseline to wk 2 0 to wk 14 changes (95% CI) Creatine Placebo Creatine Placebo Creatine Placebo Wk 0 to Wk 2 Wk 0 to Wk 14 Strength in individual muscle groups: N 20 20 19 19 17 16 Ankle Dorsiflexion (lbs) 90 (21) 101 (21) 5 (8) 6 (12) 60 (26)* 59 (27)* Ankle Plantar Flexion (lbs) 176 (44) 174 (37) 15 (21) 6 (17) 80 (39)* 68 (54)* Ankle Plantar Flexion Bent Knee (lbs) 207 (71) 176 (56) 10 (19) 23 (29) 64 (46)* 106 (67)* Leg Presses (lbs) 248 (55) 245 (54) 2 (17) 14 (29) 66 (56)* 75 (49)* Leg Curls (lbs) 106 (26) 113 (22) 6 (10) 4 (14) 43 (22)* 38 (27)* Pec Deck (lbs) 88 (23) 94 (26) 3 (9) 3 (6) 35 (15)* 32 (14)* Biceps Pushdown (lbs) 51 (14) 51 (12) 1 (4) 1 (6) 14 (10)* 12 (9)* Triceps Curls (lbs) 53 (10) 54 (11) 2 (3) 1 (6) 16 (8)* 14 (8)* Abdominal Crunches (rep) 19 (5) 17 (5) 1 (2) 1 (3) 8 (4)* 9 (5)* MVC (N) 241 (53) 240 (61) 21 (67) 27 (51) 9 (38) 39 (50) Lower Leg Flexion (N = 16) (N = 18) (N = 12) (N = 14) (N = 13) (N = 14) Muscle function (31P MRS): 15-second maximal voluntary contraction (MVC) protocol: N 17 17 13 12 14 13 At rest (before MVC): PCr (mM) 37 (2) 36 (3) 21 (3) 0 (3) 0 (3) 0 (2) 21 (23 to 1) 0 (22 to 2) Pi (mM) 5.8 (2.3) 6.1 (2.6) 0.7 (2.9) 20.4 (2.6) 0.2 (2.9) 0.2 (2.4) 1.1 (21.2 to 3.5) 0.1 (22.0 to 2.2) PCr/Pi 7.6 (3.7) 7.3 (3.6) 20.3 (6.1) 0.4 (4.8) 0.5 (6.8) 21.1 (4.0) 20.7 (25.3 to 3.8) 1.6 (22.9 to 6.1) pH 7.15(0.06) 7.12(0.05) 20.04(0.07) 20.02(0.06) 20.03(0.06) 20.02(0.05) 20.02(20.08 to 0.03) 20.01(20.06 to 0.03) Immediately following a 15-sec MVC: PCr (mM) 18 (4) 16 (5) 22 (6) 21 (5) 22 (5) 21 (8) 21 (25 to 4) 21 (26 to 5) % of resting PCr 48 (11) 44 (13) 24 (15) 24 (10) 24 (12) 23 (21) 0 (211 to 10) 21 (214 to 13) Pi (mM) 23 (6) 25 (6) 2 (8) 2 (4) 22 (6) 0 (8) 0 (25 to 6) 22 (28 to 4) PCr/Pi 0.9 (0.5) 0.7 (0.3) 0.1 (0.5) 20.1 (0.3) 0.0 (0.5) 0.0 (0.5) 0.0 (20.4 to 0.3) 0.0 (20.4 to 0.4) pH 7.09 (0.23) 7.06 (0.13) 20.11 (0.26) 0.03 (0.20) 20.02 (0.38) 0.01 (0.13) 20.14(20.34 to 0.05) 20.03(20.26 to 0.20) PCr recovery (t1/2, sec) 30 (9) 29 (12) 22 (12) 21 (15) 24 (9) 24 (16) 21 (212 to 11) 0 (210 to 11) Muscle function (31P MRS): 6 minute exercise protocol: N 15 15 10 10 12 10 At rest : PCr (mM) 37 (3) 37 (2) 21 (3) 21 (3) 0 (2) 0 (3) 0 (23 to 3) 0 (22 to 3) Pi (mM) 5.4 (2.6) 5.1 (2.4) 0.9 (3.5) 0.7 (2.9) 20.4 (1.9) 20.1 (3.1) 0.1 (22.8 to 3.1) 20.3 (22.6 to 2.0) PCr/Pi 10.0 (8.0) 9.6 (5.9) 22.7 (7.6) 22.1 (4.3) 20.9 (7.6) 0.9 (6.5) 20.6 (26.4 to 5.2) 21.8 (28.2 to 4.6) pH 7.13(0.08) 7.09(0.06) 20.03(0.08) 0.02(0.10) 0.02(0.09) 0.03(0.09) 20.05(20.13 to 0.04) 20.01(20.09 to 0.07) Immediately following the 6-minute exercise protocol: PCr (mM) 8 (7) 7 (4) 2 (6) 21 (4) 21 (6) 21 (5) 3 (22 to 7) 0 (25 to 5) % of resting PCr 23 (20) 19 (11) 5 (16) 23 (10) 22 (15) 22 (14) 8 (25 to 20) 0 (213 to 13) Pi (mM) 33 (8) 35 (5) 0 (8) 2 (4) 1 (8) 1 (7) 22 (28 to 4) 0 (27 to 7) PCr/Pi 0.4 (0.5) 0.2 (0.2) 0.1 (0.3) 20.1(0.1) 0.0 (0.4) 0.0 (0.2) 0.2 (0.0 to 0.4) 0.0 (20.3 to 0.4) pH 6.67(0.16) 6.67(0.25) 20.06 (0.18) 0.04(0.12) 20.03 (0.21) 0.07 (0.13) 20.02(20.16 to 0.13) 20.10(20.26 to 0.06) PCr recovery (t1/2, sec) 36 (16) 46 (18) 21 (28) 22 (15) 21 (17) 210 (20) 1 (221 to 22) 9 (27 to 25) 1 (218 to 20) 12 (222 to 45) 242 (283 to 1) 29 (247 to 27) 5 (213 to 22) 2 (28 to 12) 2 (25 to 9) 2 (24 to 7) 21 (24 to 2) 230 (265 to 5) Data are mean (SD). The mean differences and the 95% confidence intervals between treatment groups of the changes from baseline at weeks 2 and 14 were determined by unpaired t-tests. Asterisks (*) are used to indicate within-group changes from baseline that are statistically significant by paired t-test (P,0.05). Strength was measured as the 1 repetition maximum (1RM) for each muscle group (in pounds) except for the rectus abdominus, in which strength was assessed as the number of sit-ups completed in 30 seconds; and maximum voluntary contraction (MVC, in Newtons) of the tibialis anterior muscle, which was assessed during dorsiflexion of the right foot. Muscle function was evaluated using two exercise protocols that were performed inside a 1.9T magnet. The first protocol consisted of a 15- second maximum voluntary contraction (MVC) that was used to assess the rate of PCr recovery (an index of oxidative capacity). The second protocol consisted of 36 consecutive MVCs, one every 10 seconds, with cycles of 6 seconds of contraction and 4 seconds of relaxation. This latter protocol was used to assess muscle fatigue. Abbreviations: Rep, Repetitions; PCr, phosphocreatine; Pi, inorganic phosphate; PCr recovery (t K), time needed to recover half of the baseline PCr value. doi:10.1371/journal.pone.0004605.t002 PLoS ONE | www.plosone.org 5 February 2009 | Volume 4 | Issue 2 | e4605