Mike J. Price

Effects of sodium bicarbonate ingestion on prolonged intermittent exercise.

PURPOSE The aim of this study was to determine the effects of sodium bicarbonate ingestion on prolonged intermittent exercise and performance. METHODS Eight healthy male subjects (mean +/- SD: age 25.4 +/- 6.4 yr, mass 70.9 +/- 5.1 kg, height 179 +/- 7 cm, VO(2max) 4.21 +/- 0.51 L.min-1) volunteered for the study, which had received ethical approval. Subjects undertook two 30-min intermittent cycling trials (repeated 3-min blocks; 90 s at 40% VO(2max), 60 s at 60% VO(2max), 14-s maximal sprint, 16-s rest) after ingestion of either sodium bicarbonate (NaHCO(3); 0.3 g.kg-1) or sodium chloride (NaCl; 0.045 g x kg(-1). Expired air, blood lactate (BLa), bicarbonate (HCO(3)-), and pH were measured at rest, 30 and 60 min postingestion, and during the 40% VO(2max) component of exercise (4, 10, 16, and 29 min). RESULTS After ingestion, pH increased from rest to 7.46 +/- 0.03 and 7.40 +/- 0.01 for NaHCO(3) and NaCl, respectively (main effect for time and trial; P < 0.05). Values decreased at 15 min of exercise to 7.30 +/- 0.07 and 7.21 +/- 0.06, respectively, remaining at similar levels until the end of exercise. BLa peaked at 15 min (12.03 +/- 4.31 and 10.00 +/- 2.58 mmol.L-1, for NaHCO(3) and NaCl, respectively; P > 0.05) remaining elevated until the end of exercise (P < 0.05). Peak power expressed relative to sprint 1 demonstrated a significant main effect between trials (P < 0.05). Sprint 2 increased by 11.5 +/- 5% and 1.8 +/- 9.5% for NaHCO(3) and NaCl, respectively. During NaHCO(3), sprint 8 remained similar to sprint 1 (0.2 +/- 17%), whereas a decrease was observed during NaCl (-10.0 +/- 16.0%). CONCLUSION The results of this study suggest that ingestion of NaHCO(3) improves sprint performance during prolonged intermittent cycling.

Thermoregulation during exercise in individuals with spinal cord injuries.

The increased participation in wheelchair sports in conjunction with environmental challenges posed by the most recent Paralympic venues has stimulated interest into the study of thermoregulation of wheelchair users. This area is particularly pertinent for the spinal cord injured as there is a loss of vasomotor and sudomotor effectors below the level of spinal lesion. Studies within this area have examined a range of environmental conditions, exercise modes and subject populations. During exercise in cool conditions (15‐25°C), trained paraplegic individuals (thoracic or lumbar spinal lesions) appear to be at no greater risk of thermal injury than trained able-bodied individuals, although greater heat storage for a given metabolic rate is evident. In warm conditions (25‐40°C), trained subjects again demonstrate similar core temperature responses to the able-bodied for a given relative exercise load but elicit increased heat storage within the lower body and reduced whole-body sweat rates, increasing the risk of heat injury. The few studies examining a wide range of lesion levels have noted that, for paraplegic individuals where heat production is matched by available sweating capacity, excessive heat strain may be offset. Studies relating to tetraplegic subjects (cervical spinal lesions) are fewer in number but have consistently shown this population to elicit much faster rates of core and skin temperature increase and thermal imbalance in both cool and warm conditions than paraplegic individuals. These responses are due to the complete absence or severely reduced sweating capacity in tetraplegic subjects. During continuous exercise protocols, the main thermal stressor for tetraplegic subjects appears to be environmental heat gain, whereas during an intermittent-type exercise protocol it appears to be metabolic heat production. Fluid losses during exercise and heat retention during passive recovery from exercise are related to lesion level. Future research is recommended to focus on the specific role of absolute and relative metabolic rates, sweating responses, training status and more sport- and vocation-specific exercise protocols.

Effects of spinal cord lesion level upon thermoregulation during exercise in the heat.

PURPOSE This study examined the effects of the level of spinal cord injury upon the thermoregulatory responses of wheelchair athletes during prolonged wheelchair exercise in warm conditions. METHODS Eight tetraplegic (TP), 10 high-level paraplegic (HP), and 10 low-level paraplegic (LP) athletes exercised for 60 min at 60% [OV0312]O(2peak) in a warm environment (31.5 +/- 1.7 degrees C, 42.9 +/- 8.0% relative humidity). Skin temperature and aural temperature were monitored. RESULTS Aural temperature increased gradually during the exercise period by 1.1 +/- 0.3 and 1.4 +/- 0.5 degrees C for the HP and LP groups, with a more marked increase observed for the TP group (2.1 +/- 0.5 degrees C; P < 0.05). Upper-arm skin temperature was higher for the TP when compared with the HP and LP between 30 and 60 min (P < 0.05). Back skin temperature was higher for the TP when compared with the HP and LP between 45 and 60 min (P < 0.05). No differences were noted between groups for the thigh or calf skin temperatures. During recovery, skin temperature remained elevated for the TP group when compared with the HP and LP groups (P < 0.05). Heat storage was greatest for the TP athletes at the end of exercise and remained elevated throughout recovery (P < 0.05). CONCLUSIONS All athletes completed the exercise task even though the gradual increase in aural temperature observed for the HP and LP groups suggests a degree of thermal imbalance. However, this was much less than observed for TP athletes, who demonstrated a much greater imbalance in temperature regulation. Increasing the exercise or environmental strain may result in the thermoregulatory responses of athletes with a spinal cord injury being compromised.

The influence of crank rate on peak oxygen consumption during arm crank ergometry

The aim of this study was to assess the influence of three imposed crank rates on the attainment of peak oxygen consumption ( V O 2peak ) and other physiological responses during incremental arm crank ergometry. Twenty physically active, although non-specifically trained, males volunteered for the study. They completed an exercise protocol using an electrically braked arm ergometer (Lode Angio, Groningen, Netherlands) at crank rates of 60, 70 and 80 rev·min -1 . The order of tests was randomized and they were separated by at least 2 days. Peak V O 2 was significantly higher ( P ≪ 0.05) at 70 and 80 rev·min -1 than at 60 rev·min -1 . Peak ventilation volume increased as a function of crank rate and was higher ( P ≪ 0.05) at 80 than at 60 rev·min -1 . Peak heart rate was higher ( P ≪ 0.05) at 70 and 80 rev·min -1 than at 60 rev·min -1 . Furthermore, 70 and 80 rev·min -1 resulted in an extended test time compared with 60 rev·min -1 . The greater physiological responses observed during the tests at the two faster crank rates might have been the result of a postponement of acute localized neuromuscular fatigue, allowing for more work to be completed. We recommend, therefore, that an imposed crank rate between 70 and 80 rev·min -1 should be used to elicit V O 2peak and other physiological responses in arm crank ergometry.

Energy expenditure and metabolism during exercise in persons with a spinal cord injury.

Resting energy expenditure of persons with a spinal cord injury (SCI) is generally lower than that seen in able-bodied (AB) individuals due to the reduced amounts of muscle mass and sympathetic nervous system available. However, outside of clinical studies, much less data is available regarding athletes with an SCI. In order to predict the energy expenditure of persons with SCI, the generation and validation of prediction equations in relation to specific levels of SCI and training status are required. Specific prediction equations for the SCI would enable a quick and accurate estimate of energy requirements. When compared with the equivalent AB individuals, sports energy expenditure is generally reduced in SCI with values representing 30–75% of AB values. The lowest energy expenditure values are observed for sports involving athletes with tetraplegia and where the sport is a static version of that undertaken by the AB, such as fencing. As with AB sports there is a lack of SCI data for true competition situations due to methodological constraints. However, where energy expenditure during field tests are predicted from laboratory-based protocols, wheelchair ergometry is likely to be the most appropriate exercise mode. The physiological and metabolic responses of persons with SCI are similar to those for AB athletes, but at lower absolute levels. However, the underlying mechanisms pertaining to substrate utilization appear to differ between the AB and SCI. Carbohydrate feeding has been shown to improve endurance performance in athletes with generally low levels of SCI, but no data have been reported for mid to high levels of SCI or for sport-specific tests of an intermittent nature. Further research within the areas reviewed may help to bridge the gap between what is known regarding AB athletes and athletes with SCI (and other disabilities) during exercise and also the gap between clinical practice and performance.

The Effect of Sodium Bicarbonate Ingestion on High-Intensity Intermittent Running and Subsequent Performance

Price, MJ and Simons, C. The effect of sodium bicarbonate ingestion on high-intensity intermittent running and subsequent performance. J Strength Cond Res 24(7): 1834-1842, 2010-The purpose of this study was to determine the effects of sodium bicarbonate (NaHCO3) ingestion on intermittent running and subsequent performance. Eight healthy men volunteered to take part in the study. One hour after the ingestion of either NaHCO3 or placebo (sodium chloride; NaCl) participants undertook 20 × 24-second runs on a motorized treadmill at the velocity eliciting maximal oxygen uptake (100% v-&OV0312;o2max). After sprint 20 participants performed a run to volitional exhaustion at 120% v-&OV0312;o2max. Capillary blood samples for blood pH, bicarbonate ([HCO3−]), and lactate ([Bla]) concentration were taken pre and postingestion, every fifth sprint and after the performance run. After ingestion of NaHCO3, blood [HCO3−] increased from resting values (p < 0.05), and the increase in pH approached significance. Blood [HCO3−] continually decreased throughout intermittent exercise (p < 0.05) and decreased further after performance in both trials (p < 0.05). [Bla] was similar in both trials throughout intermittent exercise but was greater at exhaustion for NaHCO3 (main effect for trial; p < 0.05). There was no significant difference in performance of the group between trials (78 ± 22 and 75 ± 22 seconds for NaHCO3 and NaCl, respectively). The intercept of the relationships between [Bla] and [HCO3−] and between [Bla] and pH was greater during NaHCO3 (p < 0.05), whereas the relationship between pH and [HCO3−] was unchanged (p > 0.05). The results of this study suggest that the ingestion of NaHCO3− before intermittent type exercise was sufficient to induce metabolic alkalosis but did not significantly affect performance. However, because significant individual variations in performance were observed, an individual approach to bicarbonate ingestion is recommended based on the intensity and duration of the required performance.

The effects of work:rest duration on physiological and perceptual responses during intermittent exercise and performance

Abstract In this study, we examined the effects of different work:rest durations during 20 min intermittent treadmill running and subsequent performance. Nine males (mean age 25.8 years, s = 6.8; body mass 73.9 kg, s = 8.8; stature 1.75 m, s = 0.05; [Vdot]O2max 55.5 ml · kg−1 · min−1, s = 5.8) undertook repeated sprints at 120% of the speed at which [Vdot]O2max was attained interspersed with passive recovery. The work:rest ratio was constant (1:1.5) with trials involving either short (6:9 s) or long (24:36 s) work:rest exercise protocols (total exercise time 8 min). Each trial was followed by a performance run to volitional exhaustion at the same running speed. Testing order was randomized and counterbalanced. Heart rate, oxygen consumption, respiratory exchange ratio, and blood glucose were similar between trials (P > 0.05). Blood lactate concentration was greater during the long than the short exercise protocol (P < 0.05), whereas blood pH was lower during the long than the short exercise protocol (7.28, s = 0.11 and 7.30, s = 0.03 at 20 min, respectively; P < 0.05). Perceptions of effort were greater throughout exercise for the long than the short exercise protocol (16.6, s = 1.4 and 15.1, s = 1.6 at 20 min, respectively; P < 0.05) and correlated with blood lactate (r = 0.43) and bicarbonate concentrations (r = −0.59; P < 0.05). Although blood lactate concentration at 20 min was related to performance time (r = −0.56; P < 0.05), no differences were observed between trials for time to exhaustion (short exercise protocol: 95.8 s, s = 30.0; long exercise protocol: 92.0 s, s = 37.1) or physiological responses at exhaustion (P > 0.05). Our results demonstrate that 20 min of intermittent exercise involving a long work:rest duration elicits greater metabolic and perceptual strain than intermittent exercise undertaken with a short work:rest duration but does not affect subsequent run time to exhaustion.

The effects of work – rest duration on intermittent exercise and subsequent performance

This study examined the effects of different work – rest durations during 40 min intermittent treadmill exercise and subsequent running performance. Eight males (mean ± s: age 24.3 ± 2.0 years, body mass 79.4 ± 7.0 kg, height 1.77 ± 0.05 m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O2max) was attained with passive recovery between each one. The work – rest ratio was constant at 1:1.5 with trials involving short (6:9 s), medium (12:18 s) or long (24:36 s) work – rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O2max. After 40 min, mean exercise intensity was greater during the long (68.4 ± 9.3%) than the short work – rest trial (54.9 ± 8.1% [Vdot]O2max; P < 0.05). Blood lactate concentration at 10 min was higher in the long and medium than in the short work – rest trial (6.1 ± 0.8, 5.2 ± 0.9, 4.5 ± 1.3 mmol · l−1, respectively; P < 0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work – rest trials (P  < 0.05). Plasma glucose concentration was higher in the long and medium than in the short work – rest trial after 40 min of exercise (5.6 ± 0.1, 6.6 ± 0.2 and 5.3 ± 0.5 mmol · l−1, respectively; P < 0.05). No differences were observed between trials for performance time (72.7 ± 14.9, 63.2 ± 13.2, 57.6 ± 13.5 s for the short, medium and long work – rest trial, respectively; P  =  0.17), although a relationship between performance time and 40 min plasma glucose was observed (P < 0.05). The results show that 40 min of intermittent exercise involving long and medium work – rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work – rest duration.

Cooling strategies improve intermittent sprint performance in the heat of athletes with tetraplegia

Background Precooling has been shown to enhance performance in repeated sprint exercise in able-bodied subjects in a hot environment. Spinal cord injury causes thermoregulatory impairment with a detrimental effect on performance. This study assessed whether cooling strategies before and during exercise in the heat enhances sprint performance in athletes with tetraplegia. Methods Eight male athletes with tetraplegia performed intermittent arm crank exercise in the heat (32.0°C (0.1°C); humidity, 50% (0.1%)) for a maximum of 60 min or until exhaustion. Trials involved a no-cooling control (CON), precooling (PRE) or cooling during exercise (DUR). Each intermittent sprint protocol consisted of varied periods of passive rest, maximal sprinting and active recovery. Results Both PRE and DUR cooling strategies improved the ability of the athletes to repeatedly perform high-intensity sprints, with times to exhaustion (TTE), whereas during the CON trial, athletes demonstrated a reduction in the total number of sprints and TTE (47.2 (10.8), 52.8 (5.8) and 36.2 (9.6) min for CON, PRE and DUR, respectively). Core temperature was significantly higher for CON (37.3°C (0.3°C)) when compared with both PRE and DUR (36.5°C (0.6°C) and 37.0°C (0.5°C), respectively, p<0.01). Ratings of perceived exertion and thermal sensation upon exhaustion or completion were not different. Conclusions Athletes with tetraplegia should use a precooling or during-exercise cooling strategy specific to the characteristics of their sport when exercising in hot conditions.

The physiological effects of pre-event and midevent cooling during intermittent running in the heat in elite female soccer players

The purpose of this study was to examine the effects of both pre-exercise and combined pre-exercise and midexercise cooling strategies during simulated match play in elite female soccer players in the heat. Eight elite female soccer players performed two 45 min periods of intermittent running separated by 15 min seated rest on 3 separate occasions (30.6 +/- 0.2 degrees C, 63.4 +/- 2.5% relative humidity). Participants undertook a no-cooling (CON) or ice-vest cooling for 20 min pre-exercise (PRE) or both pre-exercise and during the 15 min rest period (PRE+MID). Rectal temperature (Tre), skin temperatures, and heart rate were monitored continuously. Mean skin temperature (TMS) and heat storage were calculated. Significant interactions (trial x time) were observed for the change in Tre from rest, TMS, and heat storage (p < 0.05). The change in Tre from rest was greater during CON when compared with PRE and PRE+MID from 35 min until the end of exercise (p < 0.05). When compared with CON (p < 0.05), TMS was lower after precooling (PRE and PRE+MID) and during the 15 min rest period and the first 5 min of the second exercise bout for PRE+MID. Heat storage was also lower after precooling (PRE and PRE+MID) (p < 0.05) and from 60 min until the end of exercise for PRE+MID (p < 0.05) and until 85 min and again at 95 min during PRE (p < 0.05). The results of this study suggest that both cooling strategies were effective in reducing thermal strain during intermittent exercise in the heat. However, PRE+MID cooling was more effective than PRE cooling in offsetting heat storage.