Muscle Pain as a Regulator of Cycling Intensity

Effect of Caffeine Ingestion

Alexander R. Gonglach; Carl J. Ade; Michael G. Bemben; Rebecca D. Larson; Christopher D. Black

Disclosures

Med Sci Sports Exerc. 2016;48(2):287-296. 

In This Article

Results

Assessment of V̇O2peak

Mean V̇O2peak of the 13 participants was 45.8 ± 6.8 mL· kg−1·min−1 with a corresponding peak power output of 322 ± 57 W. Based on the classifications recommended by De Pauw et al.,[14] which are based on relative V̇O2peak and peak power output, 7 of our participants had a performance level of 1 (V̇O2peak < 45 mL·kg−1·min−1), and 6 were had a performance level of 2 (V̇O2peak of 45 to 54.9 mL·kg−1·min−1). Gas exchange threshold was determined to occur at 2.11 ± 0.40 L·min−1, which was equal to 61% ± 10% of V̇O2peak.

Cycling at a Pain Rating of "3"

Participants covered greater distance (mean improvement of 591 m; t 12 = 3.15; 95% CI, 182–1000; P = 0.008) and performed more work (mean improvement of 8.9 kJ; t 12 = 3.16; 95% CI, 2.8–15.10; P = 0.008) after caffeine ingestion compared with placebo (Fig. 3A). Mean power output [mean improvement 11 W; t 12 = 3.10; 95% CI, 3.4–19.3; P = 0.009), mean V̇O2 (mean increase of 2.4 mL·kg−1·min−1; t 12 = 2.71; 95% CI, 0.47–4.2; P = 0.019), mean HR (mean increase of 2.4 bpm; t 12 = 2.71; 95% CI, 0.47–4.2; P = 0.036), and mean V̇O2 expressed as a relative percentage of GET (mean increase of 9.2%; t 12 = 2.36; 95% CI, 0.72–17.7; P = 0.012) across the 15-min exercise bout were also higher in the caffeine condition (Table 1). RER (t 12 = 1.2; 95% CI, -0.12 to 0.04; P = 0.251), ratings of muscle pain (t 12 = -1.14; 95% CI, -0.13 to 0.04; P = 0.273), and RPE (t 12 = 0.28; 95% CI, -0.42 to 0.54; P = 0.786) were not different compared with the placebo condition (Table 1). When data were broken into 3-min epochs, a significant condition–time interaction was found for distance covered during each individual 3-min epoch (F 4,48 = 4.23; P = 0.015; Figure 3B). No differences were found across the epochs over time in either the caffeine (F 4,48 = 1.69; P = 0.264) or placebo F 4,48 = 1.41; P = 0.241) conditions. Comparisons between the caffeine and placebo conditions during each 3-min epoch found significantly greater distance was covered during the caffeine condition compared with placebo during the fourth (minutes 10–12) and fifth (minutes 13–15) epochs (mean difference of 163 m; t 12 = 3.15; 95% CI, 5.0–321.5; P = 0.008; and mean difference of 187 m; t 12 = 4.48; 95% CI, 59.5–314.5; P = 0.001, respectively). A significant condition–time interaction was also found for work performed per 3-min epoch (F 4,48 = 3.20; P = 0.033). Follow-up analysis found no significant difference over time for caffeine (F 4,48 = 1.13; P = 0.339) or placebo (F 4,48 = 1.54; P = 0.239). Comparisons between conditions during each 3-min epoch revealed significant differences between caffeine and placebo during the fifth epoch (minutes 13–15) (mean difference 2.88 kJ; t 12 = 4.44; 95% CI, 0.90–4.86; P = 0.008). Condition–time interactions were not found for V̇O2 (F 4,48 = 2.40; P = 0.11), power output (F 4,48 = 2.40; P = 0.13), HR (F 4,48 = 2.96; P = 0.07), RER (F 4,48 = 1.24; P = 0.31), RPE (F 4,48 = 2.17; P = 0.15), and ratings of muscle pain (F 4,48 = 2.18; P = 0.12). Main effects for condition were found for V̇O2 (F 1,12 = 10.81; 95% CI, 0.84–4.12; P = 0.006), power output (F 1,12 = 9.65; 95% CI, 3.4–19.2; P = 0.009), and HR (F 1,12 = 5.04; 95% CI, 0.26–17.4; P = 0.044) with higher values found during the caffeine condition. A significant main effect for time was found for V̇O2 (F 4,48 = 6.00; P = 0.019), HR (F 4,48 = 22.1; P < 0.001), RER (F 4,48; P = 0.002), and RPE (F 4,48 = 19.2; P < 0.001). V̇O2 was higher in the second epoch compared with the first (mean difference of 1.12 mL·kg−1·min−1; 95% CI, 0.01–2.30; P = 0.047) but did not differ among all other epochs (P ≥ 0.11). RER was lower in the fourth epoch compared with the first two epochs (mean difference of -0.043; 95% CI, -0.08 to -0.008; P = 0.012; and mean difference of -0.023; 95% CI, -0.04 to -0.003; P = 0.021 compared with the first and second epoch's, respectively) but was not different among all other epochs (P > 0.05). HR was higher in epochs 2 (mean difference of 5.9 bpm; 95% CI, 1.47–10.3; P = 0.006), 3 (mean difference of 8.7 bpm; 95% CI, 2.7–14.8; P = 0.003), 4 (mean difference of 12.2 bpm; 95% CI, 5.1–19.4; P = 0.001), and 5 (mean difference of 14.7 bpm; 95% CI, 6.5–23.0; P = 0.001) compared with the first epoch. RPE was higher in epochs 2 (mean difference of 0.96; 95% CI, 0.3–1.6; P = 0.004), 3 (mean difference of 1.5 bpm; 95% CI, 0.4–2.5; P = 0.004), 4 (mean difference of 2.0; 95% CI, 0.6–3.5; P = 0.004), and 5 (mean difference of 2.1; 95% CI, 0.6–3.6; P = 0.005), compared with the first epoch. RPE was higher in epochs 4 (mean difference of 1.1; 95% CI, 0.09–2.1; P = 0.03) and 5 (mean difference of 1.2; 95% CI, 0.05–2.3; P = 0.04) compared with the second epoch. RPE was also higher in epochs 4 (mean difference of 0.6; 95% CI, 0.03–1.1; P = 0.03) and 5 (mean difference of 0.7; 95% CI, 0.001-1.3; P = 0.05) compared with the third epoch.

Figure 3.

Total distance covered and work performed while exercising at a muscle pain rating of ''3'' (A).Mean distance covered per 3-min epoch while exercising at a muscle pain rating of ''3'' (B). *Significant difference (P e 0.05) between caffeine and placebo conditions. Values are mean ± SD.

Cycling at a Pain Rating of "5.". Total distance covered (t 8 = 1.5; 95% CI, -100 to 475; P = 0.172) and work performed (t 8 = 1.7; 95% CI, -1.2 to 7.5; P = 0.132) did not differ between the conditions (Fig. 4A). Mean power output (t 8 = 1.9; 95% CI, -1.5 to 13.7; P = 0.10), mean V̇O2 (t 8 = 1.72; 95% CI, -0.52 to 3.56; P = 0.124), mean V̇O2 expressed as a relative percentage of GET (t 8 = 1.82; 95% CI, -0.01 to 0.12; P = 0.11), mean RER (t 8 = 0.72; 95% CI, -0.01 to 0.03; P = 0.49), mean muscle pain ratings (t 8 = 1.0; 95% CI, -0.03 to 0.07; P = 0.347), and mean RPE (t 8 = 0.47; 95% CI, -0.52 to 0.79; P = 0.65) were not different over the 10-min exercise bout between conditions (Table 2). HR was elevated (mean difference of 6.7 bpm; t 8 = 2.81; 95% CI, 1.2–12.1; P = 0.02) in the caffeine condition (Table 2). Data were broken into 2-min epochs (5 in total) for further comparison. Condition–time interactions were not found for distance covered (F 4,32 = 0.44; P = 0.67; Figure 4B), work performed (F 4,32 = 0.59; P = 0.57), V̇O2 (F 4,32 = 0.97; P = 0.40), power output (F 4,32 = 0.54; P = 0.58), HR (F 4,32 = 2.2; P = 0.17), RER (F 4,32 = 1.35; P = 0.29), RPE (F 4,32 = 1.36; P = 0.27), and ratings of muscle pain (F 4,32 = 0.34; P = 0.35) per epoch. A main effect for condition was found for HR (mean difference of 6.4 bpm; F 1,8 = 7.6; 95% CI, 1.1–11.8; P = 0.03) with higher values in the caffeine condition. A significant main effect for time was found for HR (F 4,32; P = 0.003) and RPE (F 4,32 = 37.5; P < 0.001). HR was higher in epochs 2 (mean difference of 4.6 bpm; 95% CI, 0.54–8.6; P = 0.03), 3 (mean difference of 13.6 bpm; 95% CI, 0.24–27.0; P = 0.045), 4 (mean difference of 11.8 bpm; 95% CI, 5.6–18.1; P = 0.001), and 5 (mean difference of 15.1 bpm; 95% CI, 8.2–21.9; P < 0.001) compared with the first epoch, as well as epochs 4 (mean difference of 7.3 bpm; 95% CI, 3.1–11.4; P = 0.001) and 5 (mean difference of 10.5 bpm; 95% CI, 6.6–14.5; P < 0.001) compared with the second epoch. RPE was higher in epochs 3 (mean difference of 1.4; 95% CI, 0.5–2.3; P = 0.003), 4 (mean difference of 2.1; 95% CI, 0.8–3.3; P = 0.001), and 5 (mean difference of 2.4; 95% CI, 1.0–3.8; P = 0.002) compared with the first epoch. Epochs 3 (mean difference of 0.7; 95% CI, 0.3–1.2; P = 0.003), 4 (mean difference of 1.4; 95% CI, 0.6–2.2; P = 0.001), and 5 (mean difference of 1.7; 95% CI, 0.8–2.7; P = 0.007) compared with the second epoch, and epochs 4 (mean difference of 0.7; 95% CI, 0.1–1.2; P = 0.02) and 5 (mean difference of 1.0; 95% CI, 0.3–1.7; P = 0.007) compared with the third epoch. Main effects for time were not found for distance (F 4,32 = 2.9; P = 0.09), work performed (F 4,32 = 2.4; P = 0.15), V̇O2 (F 4,32; P = 0.06), power output (F 4,32 = 0.45; P = 0.58), RER (F 4,32 = 4.4; P = 0.06), and muscle pain (F 4,32 = 2.7; P = 0.13).

Figure 4.

Total distance covered and work performed while exercising at a muscle pain rating of ''5'' (A). Mean distance covered per 2-min epoch while exercising at a muscle pain rating of ''5'' (B). Values are mean ± SD.

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