Chocolate Milk as a Post-Exercise Recovery Aid

Is peak oxygen uptake a determinant of moderate-duration self-paced exercise performance in the heat?

This study aimed to identify whether reductions in peak oxygen uptake (VO2peak) dictate performance outcomes during 30 min of self-paced exercise in the heat, which is expected to induce minimal hyperthermia. On 4 occasions, 11 male subjects completed peak and self-paced exercise in both hot (HOT, 40.2 ± 0.3 °C) and moderate (MOD; 20.4 ± 0.7 °C) conditions. During peak exercise, submaximal oxygen uptake (VO2) was ∼8% higher in HOT, but VO2peak (MOD, 4.64 ± 0.83 L·min–1; HOT, 4.54 ± 0.77 L·min–1) and peak cardiac output (Qpeak) were similar. Self-paced exercise performance was reduced by ∼21% in HOT. VO2 was similar through 15 min, but lower in HOT thereafter. Relative to MOD, this represented a higher and lower %VO2peak during the initial and latter stages. Cardiac output was similar in both trials (MOD, 31.6 ± 6.6 L·min–1; HOT, 30.1 ± 6.0 L·min–1), representing a similar percentage of Qpeak throughout. Rectal temperature was similar in both conditions until 30 min (MOD, 38.5 ± 0.3 °C; HOT, 38.7 ± 0.3 °C), while skin temperature was higher throughout in HOT (mean: MOD, 32.4 ± 1.1 °C; HOT, 37.3 ± 0.4 °C). Perceived exertion rose similarly in both conditions, while thermal discomfort was higher in HOT. These data indicate that when only skin temperature is elevated, reductions in exercise performance during moderate-duration self-paced exercise are not associated with changes in VO2peak. Rather, increases in VO2 at a given submaximal external workload and (or) thermal discomfort appear to play a larger role.

Aerobic exercise training adaptations are increased by postexercise carbohydrate-protein supplementation

Carbohydrate-protein supplementation has been found to increase the rate of training adaptation when provided postresistance exercise. The present study compared the effects of a carbohydrate and protein supplement in the form of chocolate milk (CM), isocaloric carbohydrate (CHO), and placebo on training adaptations occurring over 4.5 weeks of aerobic exercise training. Thirty-two untrained subjects cycled 60 min/d, 5 d/wk for 4.5 wks at 75-80% of maximal oxygen consumption (VO(2) max). Supplements were ingested immediately and 1 h after each exercise session. VO(2) max and body composition were assessed before the start and end of training. VO(2) max improvements were significantly greater in CM than CHO and placebo. Greater improvements in body composition, represented by a calculated lean and fat mass differential for whole body and trunk, were found in the CM group compared to CHO. We conclude supplementing with CM postexercise improves aerobic power and body composition more effectively than CHO alone.

Effects of ingesting protein in combination with carbohydrate during exercise on endurance performance: a systematic review with meta-analysis

Coingestion of protein with carbohydrate has been shown to enhance muscle recovery, particularly after intense bouts of exercise. However, performance benefits of ingesting a protein-carbohydrate drink during exercise remains unclear. Therefore, we used a systematic review with meta-analysis to examine the influence of protein ingestion during exercise on subsequent endurance performance. Eleven qualifying studies were included that contained 3 time-trial and 8 time-to-exhaustion cycling protocols. Only 3 of these studies controlled for caloric content and contained an isocaloric trial. Of the 11, 4 reported significant differences between a control and protein trial; however, none of these were isocaloric studies. The 3 time-trial protocols showed no significant improvement with protein. The meta-analysis of the time-trial studies revealed no significant overall effect (p = 0.73), whereas meta-analysis of time-to-exhaustion studies revealed a significant effect (p = 0.008). Of the time-to-exhaustion trials, the isocaloric studies found no significant effect (p = 0.71), whereas the isocarbohydrate studies revealed a significant effect (p = 0.05). The average percent improvement with ingestion of protein was 9.0%. The isocarbohydrate studies reported an improvement of 10.5%, whereas the isocaloric studies revealed a 3.4% improvement. We conclude that compared to carbohydrate alone, coingestion of protein and carbohydrate during exercise demonstrated an ergogenic effect on endurance performance when assessed by time to exhaustion and also where supplements were matched for carbohydrate (isocarbohydrate). Thus, the ergogenic effect of protein seen in isocarbohydrate studies may be because of a generic effect of adding calories (fuel) as opposed to a unique benefit of protein. Further research is warranted before a clear conclusion can be drawn.

Effects of chocolate milk consumption on markers of muscle recovery following soccer training: a randomized cross-over study

Background

The efficacy of chocolate milk (CM) as a recovery beverage following a period of increased training duration (ITD) was studied in intercollegiate soccer players.

Methods

13 subjects completed one week of normal 'baseline' training followed by four days of ITD. After each day of ITD, subjects received either a high-carbohydrate (504 kcal; CHO: 122 g; 2 g Fat) or isocaloric CM (504 kcal; 84 g CHO; 28 g Pro; 7 g Fat) recovery beverage. Serum creatine kinase (CK), myoglobin (Mb), muscle soreness, fatigue ratings and isometric quadriceps force (MVC) were obtained prior to ITD, and following 2- and 4-days of ITD. Performance tests (T-drill, vertical jump) were performed within training sessions. Treatments were administered in a randomly counterbalanced protocol, and subjects repeated the procedures with the alternate beverage following a two-week washout period.

Results

Mean daily training time and HR increased (p < 0.05) between baseline training and ITD, with no differences between treatments. No treatment*time effects were observed for Mb, muscle soreness, fatigue ratings and MVC. However, serum CK was significantly lower (p < 0.05) following four days of ITD with CM (316.9 ± 188.3 U·L^-1) compared to CHO (431.6 ± 310.8 U·L^-1). No treatment differences were observed for the performance tests.

Conclusions

Post-exercise CM provided similar muscle recovery responses to an isocaloric CHO beverage during four-days of ITD. Future studies should investigate if the attenuated CK levels observed with CM have functional significance during more demanding periods of training.

Acute effects of chocolate milk and a commercial recovery beverage on postexercise recovery indices and endurance cycling performance

To maximize training quality, athletes have sought nutritional supplements that optimize recovery. This study compared chocolate milk (CHOC) with a carbohydrate replacement beverage (CRB) as a recovery aid after intense exercise, regarding performance and muscle damage markers in trained cyclists. Ten regional-level cyclists and triathletes (maximal oxygen uptake 55.2 +/- 7.2 mL.kg(-1).min(-1)) completed a high-intensity intermittent exercise protocol, then 15-18 h later performed a performance trial at 85% of maximal oxygen uptake to exhaustion. Participants consumed 1.0 g carbohydrate.kg-1.h-1 of a randomly assigned isocaloric beverage (CHOC or CRB) after the first high-intensity intermittent exercise session. The same protocol was repeated 1 week later with the other beverage. A 1-way repeated measures analysis of variance revealed no significant difference (p = 0.91) between trials for time to exhaustion at 85% of maximal oxygen uptake (CHOC 13 +/- 10.2 min, CRB 13.5 +/- 8.9 min). The change in creatine kinase (CK) was significantly (p < 0.05) greater in the CRB trial than in the CHOC trial (increase CHOC 27.9 +/- 134.8 U.L(-1), CRB 211.9 +/- 192.5 U.L(-1)), with differences not significant for CK levels before the second exercise session (CHOC 394.8 +/- 166.1 U.L(-1), CRB 489.1 +/- 264.4 U.L(-1)) between the 2 trials. These findings indicate no difference between CHOC and this commercial beverage as potential recovery aids for cyclists between intense workouts.

Improved endurance capacity following chocolate milk consumption compared with 2 commercially available sport drinks

This study examined the effects of 3 recovery drinks on endurance performance following glycogen-depleting exercise. Nine trained male cyclists performed 3 experimental trials, in a randomized counter-balanced order, consisting of a glycogen-depleting trial, a 4-h recovery period, and a cycle to exhaustion at 70% power at maximal oxygen uptake. At 0 and 2 h into the recovery period, participants consumed chocolate milk (CM), a carbohydrate replacement drink (CR), or a fluid replacement drink (FR). Participants cycled 51% and 43% longer after ingesting CM (32 ± 11 min) than after ingesting CR (21 ± 8 min) or FR (23 ± 8 min). CM is an effective recovery aid after prolonged endurance exercise for subsequent exercise at low-moderate intensities.

Recovery from a cycling time trial is enhanced with carbohydrate-protein supplementation vs. isoenergetic carbohydrate supplementation

Background

In this study we assessed whether a liquid carbohydrate-protein (C+P) supplement (0.8 g/kg C; 0.4 g/kg P) ingested early during recovery from a cycling time trial could enhance a subsequent 60 min effort on the same day vs. an isoenergetic liquid carbohydrate (CHO) supplement (1.2 g/kg).

Methods

Two hours after a standardized breakfast, 15 trained male cyclists completed a time trial in which they cycled as far as they could in 60 min (AM_ex) using a Computrainer indoor trainer. Following AM_ex, subjects ingested either C+P, or CHO at 10, 60 and 120 min, followed by a standardized meal at 4 h post exercise. At 6 h post AM_ex subjects repeated the time trial (PM_ex).

Results

There was a significant reduction in performance for both groups in PM_ex versus AM_ex. However, performance and power decreases between PM_ex and AM_ex were significantly greater (p ≤ 0.05) with CHO (-1.05 ± 0.44 km and -16.50 ± 6.74 W) vs C+P (-0.30 ± 0.50 km and -3.86 ± 6.47 W). Fat oxidation estimated from RER values was significantly greater (p ≤ 0.05) in the C+P vs CHO during the PM_ex, despite a higher average workload in the C+P group.

Conclusion

Under these experimental conditions, liquid C+P ingestion immediately after exercise increases fat oxidation, increases recovery, and improves subsequent same day, 60 min efforts relative to isoenergetic CHO ingestion.

Milk: the new sports drink? A Review

There has been growing interest in the potential use of bovine milk as an exercise beverage, especially during recovery from resistance training and endurance sports. Based on the limited research, milk appears to be an effective post-resistance exercise beverage that results in favourable acute alterations in protein metabolism. Milk consumption acutely increases muscle protein synthesis, leading to an improved net muscle protein balance. Furthermore, when post-exercise milk consumption is combined with resistance training (12 weeks minimum), greater increases in muscle hypertrophy and lean mass have been observed. Although research with milk is limited, there is some evidence to suggest that milk may be an effective post-exercise beverage for endurance activities. Low-fat milk has been shown to be as effective, if not more effective, than commercially available sports drinks as a rehydration beverage. Milk represents a more nutrient dense beverage choice for individuals who partake in strength and endurance activities, compared to traditional sports drinks. Bovine low-fat fluid milk is a safe and effective post exercise beverage for most individuals, except for those who are lactose intolerant. Further research is warranted to better delineate the possible applications and efficacy of bovine milk in the field of sports nutrition.

Recovery nutrition: timing and composition after endurance exercise

Consumption of macronutrients, particularly carbohydrate (CHO) and possibly a small amount of protein, in the early recovery phase after endurance exercise can enhance muscle glycogen resynthesis rates. A target of at least 1.2 g x kg body weight(-1) x h(-1) CHO (over several hours) is suggested. This rate of CHO intake could be sustained with liquid, gel, or solid food rich in CHO for maximizing muscle glycogen. Whether the coingestion of protein with CHO compared with isocaloric CHO results in meaningful differences in glycogen replenishment that translate into subsequent performance enhancement is equivocal. Advantages of added protein with CHO in reducing true muscle damage from endurance exercise remain to be verified. There are, however, no apparent contraindications for using milk or specialty CHO/protein/amino acid products either. Future investigations that examine signaling mechanisms within muscle should be conducted in parallel with translational evidence in humans.

Effects of milk ingestion on prolonged exercise capacity in young, healthy men

OBJECTIVE

The effects of fluid intake during prolonged exercise have been extensively studied but at present there exists little information on the effects of milk-based drinks on the response to prolonged exercise. Thus, the purpose of this study was to investigate the effects of milk-based drinks on exercise capacity.

METHODS

Eight healthy males (age 24 +/- 4 y, height 1.76 +/- 0.04 m, mass 68.9 +/- 9.5 kg, body fat 12.5 +/- 2.4%, peak oxygen consumption 4.3 +/- 0.6 L/min) exercised to volitional exhaustion at 70% peak oxygen consumption on four occasions. Subjects ingested 1.5 mL/kg body mass of plain water, a carbohydrate-electrolyte solution, low-fat (0.1%) milk, or low-fat (0.1%) milk with added glucose before and every 10 min during exercise. The effect of the drink on exercise capacity and the cardiovascular, metabolic, and thermoregulatory responses to prolonged exercise were examined.

RESULTS

Exercise time to exhaustion was not significantly influenced by the drink ingested (P = 0.19), but there was a tendency for subjects to exercise longer when the carbohydrate-electrolyte (110.6, range 82.0-222.7 min), milk (103.3, range 85.7-228.5 min), or milk plus glucose (102.8, range 74.3-167.1 min) was ingested compared with water (93.3, range 82.4-192.3 min). The solution ingested did not influence the cardiovascular, metabolic, or thermoregulatory response to exercise.

CONCLUSION

The results of this study suggest that although the low-fat milk-based fluids did not enhance exercise capacity over that seen with the ingestion of plain water, the effect was comparable to that observed with a carbohydrate-electrolyte beverage.

The influence of carbohydrate and protein ingestion during recovery from prolonged exercise on subsequent endurance performance

Ingesting carbohydrate plus protein following prolonged exercise may restore exercise capacity more effectively than ingestion of carbohydrate alone. The objective of the present study was to determine whether this potential benefit is a consequence of the protein fraction per se or simply due to the additional energy it provides. Six active males participated in three trials, each involving a 90-min treadmill run at 70% maximal oxygen uptake (run 1) followed by a 4-h recovery. At 30-min intervals during recovery, participants ingested solutions containing: (1) 0.8 g carbohydrate x kg body mass (BM)(-1) h(-1) plus 0.3 g kg(-1) h(-1) of whey protein isolate (CHO-PRO); (2) 0.8 g carbohydrate x kg BM(-1) h(-1) (CHO); or (3) 1.1 g carbohydrate x kg BM(-1) h(-1) (CHO-CHO). The latter two solutions matched the CHO-PRO solution for carbohydrate and for energy, respectively. Following recovery, participants ran to exhaustion at 70% maximal oxygen uptake (run 2). Exercise capacity during run 2 was greater following ingestion of CHO-PRO and CHO-CHO than following ingestion of CHO (P< or = 0.05) with no significant difference between the CHO-PRO and CHO-CHO treatments. In conclusion, increasing the energy content of these recovery solutions extended run time to exhaustion, irrespective of whether the additional energy originated from sucrose or whey protein isolate.

Milk as an effective post-exercise rehydration drink

The effectiveness of low-fat milk, alone and with an additional 20 mmol/l NaCl, at restoring fluid balance after exercise-induced hypohydration was compared to a sports drink and water. After losing 1.8 (sd 0.1) % of their body mass during intermittent exercise in a warm environment, eleven subjects consumed a drink volume equivalent to 150 % of their sweat loss. Urine samples were collected before and for 5 h after exercise to assess fluid balance. Urine excretion over the recovery period did not change during the milk trials whereas there was a marked increase in output between 1 and 2 h after drinking water and the sports drink. Cumulative urine output was less after the milk drinks were consumed (611 (sd 207) and 550 (sd 141) ml for milk and milk with added sodium, respectively, compared to 1184 (sd 321) and 1205 (sd 142) ml for the water and sports drink; P < 0.001). Subjects remained in net positive fluid balance or euhydrated throughout the recovery period after drinking the milk drinks but returned to net negative fluid balance 1 h after drinking the other drinks. The results of the present study suggest that milk can be an effective post-exercise rehydration drink and can be considered for use after exercise by everyone except those individuals who have lactose intolerance.