Taurine in sports and exercise.

BACKGROUND: Taurine has become a popular supplement among athletes attempting to improve performance. While the effectiveness of taurine as an ergogenic aid remains controversial, this paper summarizes the current evidence regarding the efficacy of taurine in aerobic and anaerobic performance, metabolic stress, muscle soreness, and recovery. METHODS: Google Scholar, Web of Science, and MedLine (PubMed) searches were conducted through September 2020. Peer-reviewed studies that investigated taurine as a single ingredient at dosages of < 1 g - 6 g, ranging from 10 to 15 min-to-2 h prior to exercise bout or chronic dose (7 days- 8 weeks) of consumption were included. Articles were excluded if taurine was not the primary or only ingredient in a supplement or food source, not published in peer-reviewed journals, if participants were older than 50 years, articles published before 1999, animal studies, or included participants with health issues. A total of 19 studies met the inclusion criteria for the review. RESULTS: Key results include improvements in the following: VO2max, time to exhaustion (TTE; n = 5 articles), 3 or 4 km time-trial (n = 2 articles), anaerobic performance (n = 7 articles), muscle damage (n = 3 articles), peak power (n = 2 articles), recovery (n = 1 article). Taurine also caused a change in metabolites: decrease in lactate, creatine kinase, phosphorus, inflammatory markers, and improved glycolytic/fat oxidation markers (n = 5 articles). Taurine dosing appears to be effective at ~ 1-3 g/day acutely across a span of 6-15 days (1-3 h before an activity) which may improve aerobic performance (TTE), anaerobic performance (strength, power), recovery (DOMS), and a decrease in metabolic markers (creatine kinase, lactate, inorganic phosphate). CONCLUSIONS: Limited and varied findings prohibit definitive conclusions regarding the efficacy of taurine on aerobic and anaerobic performance and metabolic outcomes. There are mixed findings for the effect of taurine consumption on improving recovery from training bouts and/or mitigating muscle damage. The timing of taurine ingestion as well as the type of exercise protocol performed may contribute to the effectiveness of taurine as an ergogenic aid. More investigations are needed to better understand the potential effects of taurine supplementation on aerobic and anaerobic performance, muscle damage, metabolic stress, and recovery.

Downhill Running Impairs Activation and Strength of the Elbow Flexors.

ABSTRACT: Brandenberger, KJ, Warren, GL, Ingalls, CP, Otis, JS, and Doyle, JA. Downhill running impairs activation and strength of the elbow flexors. J Strength Cond Res 35(8): 2145-2150, 2021-The purpose of this study was to determine if knee extensor injury induced by 1 hour of downhill running attenuated force production in the elbow flexors. Subjects completed either downhill running for 1 hour (injured group; n = 6) or sedentary behavior (control group; n = 6). Strength and voluntary activation (%VA) were measured by isometric twitch interpolation of the elbow flexor and knee extensor muscles at the following time points in relation to the injury: before injury (Pre), after injury (Post), 24 hours after injury (24Post), and 48 hours after injury (48Post). Mean (±SE) knee extensor strength was significantly reduced (53.5 ± 9.9%) Post and remained reduced at 24Post and 48Post in the injury group. Knee extensor muscle twitch strength was reduced Post and 24Post after the downhill run (p < 0.022). Elbow flexor muscle strength was significantly reduced Post (13.2 ± 3.9%) and 24Post (17.3 ± 4.0%). Elbow flexor muscle twitch strength was not significantly different at any time point. Elbow flexor muscle %VA was not significantly reduced compared with Pre, at Post (16.2 ± 5.1%), 24Post (20.9 ± 6.7%), or 48Post (12.9 ± 4.5%). A 1-hour downhill run significantly injured the knee extensors. The elbow flexor muscles remained uninjured, but strength of these muscles was impaired by reduced %VA. These data suggest muscle injury can lead to prolonged strength deficits in muscles distant from the injury and should be accounted for when scheduling training that may lead to delayed-onset muscle soreness.

Muscle injury after low-intensity downhill running reduces running economy.

Contraction-induced muscle injury may reduce running economy (RE) by altering motor unit recruitment, lowering contraction economy, and disturbing running mechanics, any of which may have a deleterious effect on endurance performance. The purpose of this study was to determine if RE is reduced 2 days after performing injurious, low-intensity exercise in 11 healthy active men (27.5 ± 5.7 years; 50.05 ± 1.67 VO2peak). Running economy was determined at treadmill speeds eliciting 65 and 75% of the individual's peak rate of oxygen uptake (VO2peak) 1 day before and 2 days after injury induction. Lower extremity muscle injury was induced with a 30-minute downhill treadmill run (6 × 5 minutes runs, 2 minutes rest, -12% grade, and 12.9 km·h(-1)) that elicited 55% VO2peak. Maximal quadriceps isometric torque was reduced immediately and 2 days after the downhill run by 18 and 10%, and a moderate degree of muscle soreness was present. Two days after the injury, steady-state VO2 and metabolic work (VO2 L·km(-1)) were significantly greater (4-6%) during the 65% VO2peak run. Additionally, postinjury VCO2, VE and rating of perceived exertion were greater at 65% but not at 75% VO2peak, whereas whole blood-lactate concentrations did not change pre-injury to postinjury at either intensity. In conclusion, low-intensity downhill running reduces RE at 65% but not 75% VO2peak. The results of this study and other studies indicate the magnitude to which RE is altered after downhill running is dependent on the severity of the injury and intensity of the RE test.

Echinacea purpurea supplementation does not enhance VO2max in distance runners.

Oral supplementation of Echinacea purpurea (ECH) has been reported to increase levels of serum erythropoietin and as a result improve endurance performance in untrained subjects. The purpose of this study was to determine if ECH supplementation alters maximal oxygen uptake (VO2max) in trained endurance runners. Using a double-blind design, 16 trained endurance runners (9 ECH and 7 placebo [PLA]) supplemented with either 8,000 mg·d(-1) of ECH or wheat flour (PLA) for 6 weeks. Maximal aerobic treadmill tests and blood samples were measured before and after supplementation to determine VO2max, hematocrit (Hct), and hemoglobin (Hb). VO2max, Hct, and Hb did not differ between the ECH and PLA groups before or after supplementation. Furthermore, supplementation of ECH failed to improve VO2max (67.37 ± 4.62 vs. 67.23 ± 5.82 ml·kg(-1)·min(-1)), Hct (43.57 ± 2.38 vs. 42.85 ± 1.46%), or Hb (14.93 ± 1.27 vs. 15.55 ± 0.80 g·dL(-1)) from baseline measurements. Echinacea purpurea supplementation of 8,000 mg·d(-1) for 6 weeks failed to increase VO2max, Hct, or Hb in trained endurance runners and thus does not seem to influence physiological variables that affect distance running performance.

Anaerobic work capacity's contribution to 5-km-race performance in female runners.

PURPOSE: The purpose of this study was to examine the relationship between anaerobic characteristics and 5-km-race performance in trained female cross-country runners (N = 13). METHODS: The runners performed 50-m sprints and a 5-km time trial on an outdoor 400-m track and maximal anaerobic (MART) and aerobic running tests on a motorized treadmill. Anaerobic characteristics were determined by the mean velocity of the 50-m sprint (v50m) and the peak velocity in the MART (vMART). The aerobic characteristics were obtained during the aerobic treadmill test and included maximal oxygen uptake (VO2max), running economy, and ventilatory threshold (VT). RESULTS: Both the vMART (r = .69, P < .01) and VO2max (r = .80, P < .01) correlated with the mean velocity of the 5-km (v5km). A multiple-linear-regression analysis revealed that the combination of VO2max, vMART, and VT explained 81% (R2 = .81, P < .001) of the variation seen in the v5km. The vMART accounted for 31% of the total shared variance, while the combination of VO2max and VT explained the remaining 50%. CONCLUSIONS: These results suggest that among trained female runners who are relatively matched, anaerobic energy production can effectively discriminate the v5km and explain a significant amount of the variation seen in 5-km-race performance.

Adaptation of insulin-resistance indicators to a repeated bout of eccentric exercise in human skeletal muscle.

This study determined whether disrupted glucose and insulin responses to an oral glucose-tolerance test (OGTT) induced by eccentric exercise were attenuated after a repeated bout. Female participants (n = 10, age 24.7 +/- 3.0 yr, body mass 64.9 +/- 7.4 kg, height 1.67 +/- 0.02 m, body fat 29% +/- 2%) performed 2 bouts of downhill running (DTR 1 and DTR 2) separated by 14 d. OGTTs were administered at baseline and 48 hr after DTR 1 and DTR 2. Maximum voluntary isometric quadriceps torque (MVC), subjective soreness (100-mm visual analog scale), and serum creatine kinase (CK) were assessed pre-, post-, and 48 hr post-DTR 1 and DTR 2. Insulin and glucose area under the curve (38% +/- 8% and 21% +/- 5% increase, respectively) and peak insulin (44.1 +/- 5.1 vs. 31.6 +/- 4.0 muU/ml) and glucose (6.5 +/- 0.4 vs. 5.5 +/- 0.4 mmol/L) were elevated after DTR 1, with no increase above baseline 48 hr after DTR 2. MVC remained reduced by 9% +/- 3% 48 hr after DTR 1, recovering back to baseline 48 hr after DTR 2. Soreness was elevated to a greater degree 48 hr after DTR 1 (48 +/- 6 vs. 13 +/- 3 mm), with a tendency for greater CK responses 48 hr after DTR 1 (813 +/- 365 vs. 163 +/- 43 U/L, p = .08). A novel bout of eccentric exercise confers protective effects, with subsequent bouts failing to elicit disruptions in glucose and insulin homeostasis.

An isocaloric glucose-fructose beverage's effect on simulated 100-km cycling performance compared with a glucose-only beverage.

A number of recent research studies have demonstrated that providing glucose and fructose together in a beverage consumed during exercise results in significantly higher oxidation rates of exogenous carbohydrate (CHO) than consuming glucose alone. However, there is insufficient evidence to determine whether the increased exogenous CHO oxidation improves endurance performance. The purpose of this study was to determine whether consuming a beverage containing glucose and fructose (GF) would result in improved cycling performance compared with an isocaloric glucose-only beverage (G). Nine male competitive cyclists (32.6 +/- 5.8 years, peak oxygen uptake 61.5 +/- 7.9 ml x kg(-1) x min(-1)) completed a familiarization trial and then 2 simulated 100-km cycling time trials on an electronically braked Lode cycle ergometer separated by 5-7 d. During the randomly ordered experimental trials, participants received 36 g of CHO of either G or GF in 250 ml of water every 15 min. All 9 participants completed the 100-km time trial significantly faster when they received the GF beverage than with G (204.0 +/- 23.7 vs. 220.6 +/- 36.6 min; p = .023). There was no difference at any time point between trials for blood glucose or for blood lactate. Total CHO oxidation increased significantly from rest during exercise but was not statistically significant between the GF and G trials, although there was a trend for CHO oxidation to be higher with GF in the latter stages of the time trial. Consumption of a CHO beverage containing glucose and fructose results in improved 100-km cycling performance compared with an isocaloric glucose-only beverage.

Carbohydrate-protein drinks do not enhance recovery from exercise-induced muscle injury.

This study examined the effects of carbohydrate (CHO), carbohydrate-protein (CHO+PRO), or placebo (PLA) beverages on recovery from novel eccentric exercise. Female participants performed 30 min of downhill treadmill running (-12% grade, 8.0 mph), followed by consumption of a CHO, CHO+PRO, or PLA beverage immediately, 30, and 60 min after exercise. CHO and CHO+PRO groups (n=6 per group) consumed 1.2 g x kg body weight(-1) x hr(-1) CHO, with the CHO+PRO group consuming an additional 0.3 g x kg body weight(-1) x hr(-1) PRO. The PLA group (n=6) received an isovolumetric noncaloric beverage. Maximal isometric quadriceps strength (QUAD), lower extremity muscle soreness (SOR), and serum creatine kinase (CK) were assessed preinjury (PRE) and immediately and 1, 2, and 3 d postinjury to assess exercise-induced muscle injury and rate of recovery. There was no effect of treatment on recovery of QUAD (p= .21), SOR (p= .56), or CK (p= .59). In all groups, QUAD was reduced compared with PRE by 20.6%+/-1.5%, 17.2%+/-2.3%, and 11.3%+/-2.3% immediately, 1, and 2 d postinjury, respectively (p< .05). SOR peaked at 2 d postinjury (PRE vs. 2 d, 3.1+/-1.0 vs. 54.0+/-4.8 mm, p< .01), and serum CK peaked 1 d postinjury (PRE vs. 1 d, 138+/-47 vs. 757+/-144 U/L, p< .01). In conclusion, consuming a CHO+PRO or CHO beverage immediately after novel eccentric exercise failed to enhance recovery of exercise-induced muscle injury differently than what was observed with a PLA drink.

Relationship between running velocity of 2 distances and various lactate parameters.

PURPOSE: The purpose of this study was to determine the relationship between various lactate-threshold (LT) definitions and the average running velocity during a 10-km and a 21.1-km time trial (TT). METHODS: Thirteen well-trained runners completed an incremental maximal exercise test, a 10-km TT, and a 21.1-km TT on a motorized treadmill. Blood samples were collected through a venous catheter placed in an antecubital vein. Pearson's correlation coefficients were used to determine the relationship between the running velocity at the different LT definitions and the average running velocity during each TT. A dependent t test was used to determine statistical differences for the mean lactate response between the 2 running distances. RESULTS: The LT(Dmax), the point on the regression curve that yielded the maximal perpendicular distance to the straight line formed by the 2 endpoints, was the LT definition with the highest correlation for both 10-km (r = .844) and 21.1-km TTs (r = .783). The velocity at the LT(Dmax) was not, however, the velocity closest to the performance velocity for either distance. The mean running velocity at each LT was significantly different and tended to overestimate the mean TT performance velocities. The mean lactate concentration during the 10-km TT (3.52 + or - 1.58 mmol) was significantly higher than during the 21.1-km TT (1.86 + or - 0.90 mmol). CONCLUSION: These results indicate that a single LT point cannot be reliably associated with different running distances. Furthermore, these data suggest that a different methodology for estimating the LT that considers individual responses might be required for different running distances.

Recovery from run training: efficacy of a carbohydrate-protein beverage?

Post-exercise nutrition is critical to facilitate recovery from training. To determine if added protein (P) or increased carbohydrate (CHO) differentially improves recovery, eight runners ingested: 6% CHO (CHO6), 8% CHO + 2% protein (CHO-P), and isocaloric 10% CHO (CHO10) following a 21-km run plus treadmill run to fatigue (RTF) at 90% VO2max. RTF was repeated after 2 h recovery. After 24 h, a 5 km time trial was performed. Insulin and blood glucose were higher (P < 0.05) following CHO10 compared to CHO-P and CHO6, but did not affect improvement from the first to second RTF (29.6% +/- 6, 40.5% +/- 8.8, 40.5% +/- 14.5) or 5 km time (1100 +/- 36.3, 1110 +/- 37.3, 1118 +/- 36.5 s). CK was not different, but perceived soreness with CHO-P (2.1 +/- 0.5) was lower than CHO10 (5.2 +/- 0.7). Additional calories from CHO or P above that provided in sports drinks does not improve subsequent performance after recovery; but less soreness suggests benefits with CHO-P.

Exercise level and energy expenditure in the TAKE 10! in-class physical activity program.

This study evaluated the effectiveness of an innovative, classroom-based physical activity prevention program designed to integrate academic curriculum elements along with a physical activity program in providing moderate-to-vigorous intensity physical activity. A convenience sample of three public school classrooms (one first, third, and fifth grade class) was observed implementing the TAKE 10! program while monitored by either CSA accelerometers or digital pedometers. Pedometer step counts and CSA data were recorded for each student and activity. As calculated from CSA data, average MET levels during the activities were 5.72-7.05 (first grade), 5.51-6.77 (third grade), and 4.98-7.19 (fifth grade), and levels were not different between grades (p > 0.05). Average caloric expenditure (Kcal) per 10-minute session was 25.6-27.8 (first grade), 27.6-33.9 (third grade), and 29.7-42.9 (fifth grade). Measured pedometer step counts per session ranged from 644-931 in first grade, 659-1, 376 in third grade, and 1002-1041 in fifth grade. TAKE 10! sessions for all three grades produced exercise levels in the moderate intensity range throughout full duration of the session. Classroom-based physical activity promotion provides a useful strategy to promote meaningful physical activity among school children.