Beau K. Greer

Effect of carbohydrate-protein supplement timing on acute exercise-induced muscle damage

PurposeTo determine if timing of a supplement would have an effect on muscle damage, function and soreness.MethodsTwenty-seven untrained men (21 ± 3 yrs) were given a supplement before or after exercise. Subjects were randomly assigned to a pre exercise (n = 9), received carbohydrate/protein drink before exercise and placebo after, a post exercise (n = 9), received placebo before exercise and carbohydrate/protein drink after, or a control group (n = 9), received placebo before and after exercise. Subjects performed 50 eccentric quadriceps contractions on an isokinetic dynamometer. Tests for creatine kinase (CK), maximal voluntary contraction (MVC) and muscle soreness were recorded before exercise and at six, 24, 48, 72, and 96 h post exercise. Repeated measures ANOVA were used to analyze data.ResultsThere were no group by time interactions however, CK significantly increased for all groups when compared to pre exercise (101 ± 43 U/L) reaching a peak at 48 h (661 ± 1178 U/L). MVC was significantly reduced at 24 h by 31.4 ± 14.0%. Muscle soreness was also significantly increased from pre exercise peaking at 48 h.ConclusionEccentric exercise caused significant muscle damage, loss of strength, and soreness; however timing of ingestion of carbohydrate/protein supplement had no effect.

BRANCHED-CHAIN AMINO ACID SUPPLEMENTATION LOWERS PERCEIVED EXERTION BUT DOES NOT AFFECT PERFORMANCE IN UNTRAINED MALES

Greer, BK, White, JP, Arguello, EM, and Haymes, EM. Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males. J Strength Cond Res 25(2): 539-544, 2011-The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation affects aerobic performance, ratings of perceived exertion (RPE), or substrate utilization as compared with an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo (PLAC) beverage. Nine untrained males performed three 90-minute cycling bouts at 55% &OV0312;o2 peak followed by 15-minute time trials. Subjects, who were blinded to beverage selection, ingested a total of 200 kcal via the CHO or BCAA beverage before and at 60 minutes of exercise or the PLAC beverage on the same time course. RPE and metabolic measurements were taken every 15 minutes during steady-state exercise, and each of the trials was separated by 8 weeks. Plasma glucose and BCAA concentrations were measured pre- and post-exercise. A greater distance (4.6 ± 0.6 km) was traveled in the time-trial during the CHO trial than the PLAC trial (3.9 ± 0.4 km) (p < 0.05). There was no difference between the BCAA (4.4 ± 0.5 km) and PLAC trials. RPE was reduced at the 75-minute and 90-minute mark during the BCAA trial as compared with the PLAC trial. There were no significant differences found for the trial vs. time interaction in regard to respiratory exchange ratio. Thus, CHO supplementation improves performance in a loaded time-trial as compared with a PLAC beverage. BCAA supplementation, although effective at increasing blood concentrations of BCAA, did not influence aerobic performance but did attenuate RPE as compared with a PLAC beverage.

Acute arginine supplementation fails to improve muscle endurance or affect blood pressure responses to resistance training.

Greer, BK and Jones, BT. Acute arginine supplementation fails to improve muscle endurance or affect blood pressure responses to resistance training. J Strength Cond Res 25(7): 1789-1794, 2011—Dietary supplement companies claim that arginine supplements acutely enhance skeletal muscular endurance. The purpose of this study was to determine whether acute arginine α-ketoglutarate supplementation (AAKG) will affect local muscle endurance of the arm and shoulder girdle or the blood pressure (BP) response to anaerobic exercise. Twelve trained college-aged men (22.6 ± 3.8 years) performed 2 trials of exercise separated by at least 1 week. At 4 hours before, and 30 minutes before exercise, a serving of an AAKG supplement (3,700 mg arginine alpha-ketoglutarate per serving) or placebo was administered. Resting BP was assessed pre-exercise after 16 minutes of seated rest, and 5 and 10 minutes postexercise. Three sets each of chin-ups, reverse chin-ups, and push-ups were performed to exhaustion with 3 minutes of rest between each set. Data were analyzed using repeated-measures analysis of variance and paired t-tests. The AAKG supplementation did not improve muscle endurance or significantly affect the BP response to anaerobic work. Subjects performed fewer total chin-ups (23.75 ± 6.38 vs. 25.58 ± 7.18) and total trial repetitions (137.92 ± 28.18 vs. 141.08 ± 28.57) in the supplement trial (p ≤ 0.05). Subjects executed fewer reverse chin-ups (5.83 ± 1.85 vs. 6.75 ± 2.09) during set 2 after receiving the supplement as compared to the placebo (p < 0.05). Because AAKG supplementation may hinder muscular endurance, the use of these supplements before resistance training should be questioned.

EFFECTS OF LOAD-VOLUME ON EPOC AFTER ACUTE BOUTS OF RESISTANCE TRAINING IN RESISTANCE-TRAINED MEN

Abstract Abboud, GJ, Greer, BK, Campbell, SC, and Panton, LB. Effects of load-volume on EPOC after acute bouts of resistance training in resistance-trained men. J Strength Cond Res 27(7): 1936–1941, 2013—Recent investigations have shown excess postexercise oxygen consumption (EPOC) to be elevated for up to 48 hours in both untrained and trained subjects after resistance training (RT). The purpose of this study was to investigate the effect of load-volume on EPOC. Eight trained men (aged 22 ± 3 years) participated in 2 randomized RT bouts separated by at least 1 week with total load-volumes of 10,000 and 20,000 kg, respectively. Intensity of RT (85% 1 repetition maximum) did not differ between trials. Exercise energy expenditure and resting metabolic rate (RMR) were measured by indirect calorimetry at 8.5 hours before, 1.5 hours before, and during RT bouts and 12, 24, 36, and 48 hours after exercise. Creatine kinase (CK) was measured before and after RT, and 12, 24, 36, and 48 hours postexercise; ratings of perceived muscle soreness were measured on a similar time course save the immediate postexercise time point. Analysis of variance with repeated measures was used to analyze dependent variables. During the 20,000 kg trial, subjects expended significantly (p < 0.01) more energy (484 ± 29 kcal) than the 10,000 kg lift (247 ± 18 kcal). After the 20,000 kg lift, 12 hours postexercise, CK (1,159 ± 729 U·L−1) was significantly elevated (p < 0.05) as compared with baseline (272 ± 280 U·L−1) and immediately postexercise (490 ± 402 U·L−1). No significant time or trial differences were found in RMR between the 10,000 and 20,000 kg trials. In conclusion, high-intensity RT with load-volumes of up to 20,000 kg using resistance-trained men does not significantly increase EPOC above baseline RMR.

Acute Effects of Plyometric and Resistance Training on Running Economy in Trained Runners

Abstract Marcello, RT, Greer, BK, and Greer, AE. Acute effects of plyometric and resistance training on running economy in trained runners. J Strength Cond Res 31(9): 2432–2437, 2017—Results regarding the acute effects of plyometrics and resistance training (PRT) on running economy (RE) are conflicting. Eight male collegiate distance runners (21 ± 1 years, 62.5 ± 7.8 ml·kg−1·min−1 V[Combining Dot Above]O2 peak) completed V[Combining Dot Above]O2 peak and 1 repetition maximum (1RM) testing. Seven days later, subjects completed a 12 minutes RE test at 60 and 80% V[Combining Dot Above]O2 peak, followed by a PRT protocol or a rested condition of equal duration (CON). The PRT protocol consisted of 3 sets of 5 repetitions at 85% 1RM for barbell squats, Romanian deadlifts, and barbell lunges; the same volume was used for resisted lateral lunges, box jumps, and depth jumps. Subjects completed another RE test immediately after the treatments and 24 hours later. Subjects followed an identical protocol 6 days later with condition assignment reversed. Running economy was determined by both relative V[Combining Dot Above]O2 (ml·kg−1·min−1) and energy expenditure (EE) (kcal·min−1). There was a significant (p ⩽ 0.05) between-trial increase in V[Combining Dot Above]O2 (37.1 ± 4.2 ml·kg−1·min−1 PRT vs. 35.5 ± 3.9 ml·kg−1·min−1 CON) and EE (11.4 ± 1.3 kcal·min−1 PRT vs. 11.0 ± 1.4 kcal·min−1 CON) immediately after PRT at 60% V[Combining Dot Above]O2 peak, but no significant changes were observed at 80% V[Combining Dot Above]O2 peak. Respiratory exchange ratio was significantly (p ⩽ 0.05) reduced 24 hours after PRT (0.93 ± 0.0) as compared to the CON trial (0.96 ± 0.0) at 80% V[Combining Dot Above]O2 peak. Results indicate that high-intensity PRT may acutely impair RE in aerobically trained individuals at a moderate running intensity, but that the attenuation lasts less than 24 hours in duration.

Impact of Direction of Unloading Influence on Template Rate of Perceived Exertion

Abstract Greer, BK, Young, PR, Thompson, B, Rickert, BJ, and Moran, MF. Impact of direction of unloading influence on template rate of perceived exertion. J Strength Cond Res 32(12): 3407–3413, 2018—It is suggested that exercisers engage in a process of teleoanticipation and create an exercise template based on previous experience with the exercise task that guides their perceptions of the amount of effort required for task completion. This study examined how altering workload intensity during a positive-pressure treadmill task may impact Rating of Perceived Exertion (RPE). In a counterbalanced design, 15 collegiate cross-country runners (7 men and 8 women) performed 2 25-minute runs at a constant velocity, while body mass (BM) was either increased from 60 to 100% (low-to-high progression trial [INC]) or decreased from 100 to 60% (high-to-low progression trial) in 5-minutes increments. Oxygen consumption (V[Combining Dot Above]O2), heart rate (HR), and respiratory exchange ratio (RER) were collected. RPE was recorded at the end of each stage, and energy expenditure (EE) was calculated with V[Combining Dot Above]O2 and RER data. There were no significant differences between direction of loading conditions for V[Combining Dot Above]O2, EE, HR, and RER (p > 0.05). Between-trial differences in RPE at 100, 90, and 80% BM were statistically significant (p < 0.001), with higher RPEs observed during the INC. Differences in RPE observed between conditions cannot be explained by physiological mechanisms. These findings suggest that RPE is a multifaceted construct that can be impacted by subjectively based anticipatory factors such as exercise intensity.

Tibial Acceleration and Spatiotemporal Mechanics in Distance Runners During Reduced-Body-Weight Conditions

CONTEXT Treadmills that unload runners via a differential air-pressure (DAP) bladder (eg, AlterG Anti-Gravity Treadmill) are commonly used to reduce effective body weight (BW) in a clinical setting. However, the relationship between the level of unloading and tibial stress is currently unknown. OBJECTIVE To determine the relationship between tibial impact acceleration and level of BW unloading during running. DESIGN Cross-sectional. SETTING University motion-analysis laboratory. PARTICIPANTS 15 distance runners (9 male, 6 female; 20.4 ± 2.4 y, 60.1 ± 12.6 kg). MAIN OUTCOME MEASURES Peak tibial acceleration and peak-to-peak tibial acceleration were measured via a uniaxial accelerometer attached to the tibia during a 37-min continuous treadmill run that simulated reduced-BW conditions via a DAP bladder. The trial began with a 10-min run at 100% BW followed by nine 3-min stages where BW was systematically reduced from 95% to 60% in 5% increments. RESULTS There was no significant relationship between level of BW and either peak tibial acceleration or peak-to-peak tibial acceleration (P > .05). Both heart rate and step rate were significantly reduced with each 5% reduction in BW level (P < .01). CONCLUSIONS Although ground-reaction forces are reduced when running in reduced-BW conditions on a DAP treadmill, tibial shock magnitudes are unchanged as an alteration in spatiotemporal running mechanics (eg, reduced step rate) and may nullify the unloading effect.

Plyometric and Resistance Training Do Not Inhibit Running Economy for Up to 24 Hours: 1299 Board #2 June 2, 8: 00 AM - 10: 00 AM.

Many college runners supplement their run training with plyometric and resistance exercises, yet little is known about their acute effects on running performance. PURPOSE: To investigate the acute effects of plyometric and resistance training (RT) on running economy (RE) in male collegiate distance runners. METHODS: Eight male distance runners recruited from a local Division 1 college completed a VO2 peak assessment and one repetition max (1RM) testing for four lower body exercises. Two weeks after initial testing, and using a crossover design, each runner completed a continuous 12 minute RE test with six minutes at 60% and 80% VO2 peak each, followed by a one hour RT protocol or rest (CONT). Running economy was assessed via oxygen consumption (VO2) and energy expenditure (kcals/min) during the last 2 minutes of each RE test intensity. RT consisted of three sets of five reps of two plyometric exercises as well as the four lower body exercises previously tested. All resistance work was performed at 85% of 1RM. Following the RT or CONT treatment, subjects immediately completed another RE test as well as one 24 hrs later. Subjects followed an identical protocol after a one week washout period with the alternate condition (RT or CONT). VO2, respiratory exchange ratio (RER), energy expenditure (EE) and ventilation (VE) were recorded during all RE testing. Metabolic data were analyzed parametrically using a repeated measures ANOVA with a Tukey post hoc test. RESULTS: There were no significant (p > 0.05) increases in VO2 or EE immediately nor 24 hr post-RT. VE was significantly greater (p < 0.05) at 60% and 80% VO2 peak post-RT (57.01 ± 8.94, 89.26 ± 18.06 L/min) as compared to pre-RT (52.81 ± 9.36, 82.28 ± 16.37 L/min). RER was significantly greater (p < 0.05) post-RT (0.94 ± .04) compared to pre-RT (0.93 ± .04) at 80% VO2 peak. CONCLUSION: These findings indicate that high intensity RT does not significantly affect RE in male collegiate distance runners.

Use of the Wattbike Cycle Ergometer for Attenuation of Bilateral Pedaling Asymmetry in Trained Cyclists

Abstract Kell, DT and Greer, BK. Use of the Wattbike cycle ergometer for attenuation of bilateral pedaling asymmetry in trained cyclists. J Strength Cond Res 31(2): 468–473, 2017—Experienced cyclists typically pedal with a 5–20% bilateral asymmetry in regards to power output. The aim of this study was to determine if visual feedback (VF) through the Wattbike cycle ergometer is an effective tool in reducing bilateral pedaling asymmetry in trained cyclists. Twelve subjects completed three 10-minute cycling trials on the Wattbike at a power output consistent with 60% V[Combining Dot Above]O2 peak. The 3 trials consisted of a baseline (BASE) trial in which cyclists pedaled without instruction, a conscious control (CC) trial during which cyclists attempted to pedal symmetrically, and another trial in which cyclists attempted to pedal symmetrically while using VF of their bilateral power outputs (%) through the Wattbike. Although the BASE trial was always performed first, the order of the CC and VF trials was counterbalanced to minimize the influence of the order effect. For the primary analysis, the Asymmetry Index percentages (AI%s) for the 3 trials were not significantly different (p > 0.05). However, secondary analysis of subjects who had baseline AI%s within the normal, reported range showed significantly decreased AI%s during the VF trial as compared with BASE (p ⩽ 0.05). These results suggest that cyclists with normal AI%s can pedal more symmetrically while using VF of their asymmetry as opposed to merely attempting conscious correction without feedback. It is currently unknown whether adopting a more bilaterally symmetrical pedaling style will improve cycling performance or decrease injury rates in cyclists.

Reliability of BOD POD Measurements Remain High Following a Short Duration Low- Carbohydrate Diet

The purpose of the current study was to determine whether expected changes in body weight via a 3-day low-carbohydrate (LC) diet will disrupt the reliability of air displacement plethysmography measurements via BOD POD. Twenty-four subjects recorded their typical diets for 3 days before BOD POD and 7-site skinfold analyses. Subjects were matched for lean body mass and divided into low-CHO (LC) and control (CON) groups. The LC group was given instruction intended to prevent more than 50 grams/day of carbohydrate consumption for 3 consecutive days, and the CON group replicated their previously recorded diet. Body composition measurements were repeated after dietary intervention. Test-retest reliability measures were significant (p < .01) and high for body fat percentage in both the LC and the CON groups (rs = .993 and .965, respectively). Likewise, skinfold analysis for body fat percentage reliability was high in both groups (rs = .996 and .997, respectively). There were significant differences between 1st and 2nd BOD POD measurements for body mass (72.9 ± 13.3 vs. 72.1 ± 13.0 kg [M ± SD]) and body volume (69.0 ± 12.7-68.1 ± 12.2 L) in the LC group (p < .05). However, there were no differences (p > .05) in BOD POD-determined body fat percentage, lean body mass, or fat mass between the 1st and 2nd trial in either group. Body composition measures via BOD POD and 7-site skinfolds remain reliable after 3 days of an LC diet despite significant decreases in body mass.