Physiological Impact of a Single Serving Slow Absorption Carbohydrate on Metabolic, Hemodynamic, and Performance Markers in Endurance Athletes During a Bout of Exercise

ABSTRACT

Davitt, PM, Saenz, C, Hartman, T, Barone, P, and Estremera, S. Physiological impact of a single serving slow absorption carbohydrate on metabolic, hemodynamic, and performance markers in endurance athletes during a bout of exercise. J Strength Cond Res 35(5): 1262-1272, 2021-The purpose of this study was to determine how a slow-absorbing carbohydrate affected markers of metabolism, hemodynamics, and performance in well-trained endurance athletes. We examined total and exogenous carbohydrate oxidation (CHO ox), glucose, and performance after consuming different glucose beverages, before a treadmill run. Ten male runners (32.4 years; V̇o2max, 55.9 ml·kg-1·min-1) participated on 3 occasions: slow digestion CHO (S), fast digestion CHO (F), and water (W). Subjects consumed a 50 g dose of either S or F before a 3-hour treadmill run at 57% V̇o2max. Variables were assessed at -15, 0, 30, 60, 90, 135, and 180 minutes. Immediately postrun, subjects completed a time-to-fatigue test at 110% V̇o2max. There was a significant difference in CHO ox for W vs. F and S (C,1.14; S,1.52; F,1.66 ± 0.2 g·min-1, p < 0.05). Fat ox was significantly higher in S vs. F (S,0.54; F,0.47 ± 0.08 g·min-1, p < 0.05). Exogenous CHO ox was significantly higher in F vs. S (F,0.26; S,0.19 + 0.04 g·min-1, p < 0.05). There was a significant difference in average blood glucose for trial (F,94.5; S,97.1 vs. W,88.4 + 2.1 mg·dl-1) and time × trial for F vs. S (0 minutes, p < 0.05). There were no significant performance differences. Consumption of a single bolus of CHO beverage before a 3-hour run elicits significant alterations in energy metabolism compared with just water, with S CHO oxidizing significantly more fat than a rapidly digested carbohydrate. These findings suggest that slow-digesting modified starch provides a consistent blood glucose level and sustained exogenous energy supply during a sustained, 3-hour endurance run. Significance was set at p < 0.05.

Six weeks of Jilin ginseng root supplementation attenuates drop jump-related muscle injury markers in healthy female college students

BACKGROUND

Eccentric muscle contraction is an inherent component of numerous sporting movements but can result in muscle fatigue and injury, especially when engaging in unfamiliar exercise, which requires pharmacological intervention. Jilin ginseng root (GS) has been used to protect muscles and reduce the risk of exercise injury.

AIM OF THE STUDY

In this study, we sought to examine and demonstrate the effectiveness of using GS in preventing muscle stiffness and reducing the risk of exercise injury in women.

METHODS

Twenty females were randomly assigned to GS and placebo groups. Body composition, serum biochemistry index, kinematics, and endurance exercise tests were measured at two time point presupplementation and 6 weeks after supplementation. The major compounds of GS were characterized using a high-performance liquid chromatograph with a gradient delivery system (HPLC).

RESULTS

After 6 weeks of supplementation, the GS group exhibited significant increases in the serum levels of free fatty acids and glucose as well as greater maximum oxygen consumption (VO2 max, mL min-1 kg-1) compared with the placebo group in an exhaustive biking test. Following drop jump tests, the jump height and reactive strength index were increased in the GS group after completing 70 DJs. In addition, subjects in the GS group also showed decreased knee and ankle stiffness in DJs, leading to reduced fatigue associated with eccentric movement.

CONCLUSIONS

GS supplementation leads to ameliorates drop jump muscle stiffness and fatigue in females and is to be used as a nutrient supplement to reduce the risk of musculoskeletal system injuries when performing drop jumps.

The Effect of Resistance Exercise Intensity on Acute Hyperglycemia in Young Adult Males

The purpose of this study was to examine the effect of resistance exercise (RE) intensity on acute hyperglycemia, in young adult males. Thirteen males (age 23.43 ± 2.18 years, height 175.16 ± 10.44 cm, weight 77.02 ± 8.91 kg, body fat 20 ± 0.03%) participated in three randomized testing sessions, each separated by 96 h. The three testing conditions were: control (CON; induction of hyperglycemia with no-exercise), high (HI; induction of hyperglycemia followed by high-intensity RE: 5 × 4, 90% 1-repetition maximum (1-RM)), and moderate (MO; induction of hyperglycemia followed by low-intensity RE: 3 × 14, 65% 1-RM). In all three testing conditions, participants orally ingested a D100 (100 g/10 oz) glucose beverage at a dosage of 2 g glucose/kg body weight and capillary blood was obtained for plasma glucose and insulin analysis at 0 (fasting), 30, 60, 90 and 120 min, following glucose ingestion. At 30-min post-ingestion in the HI and MO conditions, participants began the respective RE protocols. Acute hyperglycemia was achieved throughout all three 2-h testing conditions; mean 2-h plasma glucose levels during CON (7.1 ± 1.3 mmol∙L⁻¹), MO (7.5 ± 0.6 mmol∙L⁻¹) and HI (8.2 ± 1.9 mmol∙L⁻¹) were all significantly (p < 0.05) greater than mean fasting plasma glucose (5.6 ± 0.46 mmol∙L⁻¹). Plasma glucose and insulin did not differ (p < 0.05) between treatment conditions at any times points over the 120 min, however, 2-h glucose area under the curve in the HI condition was significantly greater (p < 0.05) than CON and MO. In conclusion, this study indicates that hyperglycemia, induced prior to RE, may be exacerbated by high-intensity RE.

Validity of Wearable Activity Monitors during Cycling and Resistance Exercise

INTRODUCTION

The use of wearable activity monitors has seen rapid growth; however, the mode and intensity of exercise could affect the validity of heart rate (HR) and caloric (energy) expenditure (EE) readings. There is a lack of data regarding the validity of wearable activity monitors during graded cycling regimen and a standard resistance exercise. The present study determined the validity of eight monitors for HR compared with an ECG and seven monitors for EE compared with a metabolic analyzer during graded cycling and resistance exercise.

METHODS

Fifty subjects (28 women, 22 men) completed separate trials of graded cycling and three sets of four resistance exercises at a 10-repetition-maximum load. Monitors included the following: Apple Watch Series 2, Fitbit Blaze, Fitbit Charge 2, Polar H7, Polar A360, Garmin Vivosmart HR, TomTom Touch, and Bose SoundSport Pulse (BSP) headphones. HR was recorded after each cycling intensity and after each resistance exercise set. EE was recorded after both protocols. Validity was established as having a mean absolute percent error (MAPE) value of ≤10%.

RESULTS

The Polar H7 and BSP were valid during both exercise modes (cycling: MAPE = 6.87%, R = 0.79; resistance exercise: MAPE = 6.31%, R = 0.83). During cycling, the Apple Watch Series 2 revealed the greatest HR validity (MAPE = 4.14%, R = 0.80). The BSP revealed the greatest HR accuracy during resistance exercise (MAPE = 6.24%, R = 0.86). Across all devices, as exercise intensity increased, there was greater underestimation of HR. No device was valid for EE during cycling or resistance exercise.

CONCLUSIONS

HR from wearable devices differed at different exercise intensities; EE estimates from wearable devices were inaccurate. Wearable devices are not medical devices, and users should be cautious when using these devices for monitoring physiological responses to exercise.