Benefits Of Grunting In Tennis

Enhanced tennis performance with grunting is shown here. Abstract:

Grunting is widely used by professional tennis players, but no research has been done to verify enhanced performance with grunting. Therefore, the purpose of this study was to determine if grunting enhanced ball velocity in groundstrokes and secondly, to determine if grunting increased the physiological cost of hitting (VO2, HR, VE/VO2, and RPE). Participants were 10 members of the men's (n = 5) and women's (n = 5) tennis teams at a Division I university who had just completed their indoor competitive season. Two hitting sessions were used as players repetitively hit forehand and backhand shots while either grunting or not grunting. Each hitting session consisted of five 2-minute periods with a 1-minute break in between each period. Ball velocity was measured with a radar gun. During each hitting session, players wore a portable metabolic measuring unit. HR was monitored using a Polar monitor, and RPE was assessed using Borg's 6-20 scale. Grunting increased ball velocity (kph) 3.8% compared with non-grunting condition (p < 0.034) with the mean ± SD being 83.4 ± 0.6.1 and 80.3 ± 0.8.7, respectively. The physiological responses (VO2, HR, VE/VO2, and RPE) for the 2 hitting conditions were not significantly different for any variable. When averaged across both hitting conditions, HR over the 5-time periods was higher in periods 3-5 than period (p < 0.018) 1, whereas VE/VO2 and RPE were greater in periods 2-5 than period 1 (p = 0.001). RPE significantly increased over time with periods 2-5 being greater than period 1 (p = 0.001). It was concluded that grunting increased ball velocity without increasing VO2 or VE/VO2 or RPE in comparison with not grunting. It may be worthwhile for players and coaches in tennis and other sports to experiment with grunting to determine possible improvement in performance.

Benefits Of A Ketone Ester Drink

Utility of a ketone ester drink, along with adequate glucose, in enhancing muscle glycogen synthesis is shown here, abstract:

INTRODUCTION:

Physical endurance can be limited by muscle glycogen stores, in that glycogen depletion markedly reduces external work. During carbohydrate restriction, the liver synthesises the ketone bodies, D-β-hydroxybutyrate and acetoacetate, from fatty acids. In animals and in the presence of glucose, D-β-hydroxybutyrate promotes insulin secretion and increases glycogen synthesis. Here we determined whether a dietary ketone ester, combined with plentiful glucose, can increase post-exercise glycogen synthesis in human skeletal muscle.

METHODS:

Following an interval-based glycogen-depletion exercise protocol, 12 well-trained male athletes completed a randomized, 3-arm, blinded crossover recovery study that consisted of consumption of either a taste-matched, zero-calorie control or a ketone monoester drink, followed by a 10 mM glucose clamp or saline infusion for two hours. The three post-exercise conditions were; control drink then saline infusion, control drink then hyperglycemic clamp or ketone ester drink then hyperglycemic clamp. Skeletal muscle glycogen content was determined in muscle biopsies of vastus lateralis taken before and after the two-hour clamps.

RESULTS:

The ketone ester drink increased blood D-β-hydroxybutyrate concentrations to a maximum of 5.3 vs. 0.7 mM for the control drink (p < 0.0001). During the two-hour glucose clamps, insulin levels were two-fold higher (31 vs. 16 mU/l, p < 0.01) and glucose uptake 32% faster (1.66 vs. 1.26 g/kg, p<0.001). The ketone drink increased by 61 g the total glucose infused over 2 h, from 197 g to 258 g, and muscle glycogen was 50% higher (246 vs.164 mmoles glycosyl units/kg dry weight, p < 0.05) than after the control drink.

CONCLUSION:

In the presence of constant high glucose concentrations, a ketone ester drink increased endogenous insulin levels, glucose uptake and muscle glycogen synthesis.

More On Sugar And Obesity

Here is yet another study linking sugar and sweetened beverages to obesity.  The importance of avoiding excess sugar consumption and of avoiding drinking empty calories is underscored here. These sorts of dietary changes can have a large impact on overall health.