The rate at which VO2 adjusts to the new energy demand following the onset of exercise strongly influences the magnitude of the “O2 defcit” incurred and thus the extent to which muscle and systemic homeostasis is perturbed. Moreover, during continuous high-intensity exercise, there is a progressive loss of muscle contractile efficiency, which is reflected in a “slow component” increase in VO2. The factors that dictate the characteristics of these fast and slow phases of the dynamic response of VO2 following a step change in energy turnover remain obscure. However, it is clear that these features of the VO2 kinetics have the potential to influence the rate of muscle fatigue development and, therefore, to affect sports performance. This commentary outlines the present state of knowledge on the characteristics of, and mechanistic bases to, the VO2 response to exercise of different intensities. Several interventions have been reported to speed the early VO2 kinetics and/or reduce the magnitude of the subsequent VO2 slow component, and the possibility that these might enhance exercise performance is discussed.
Andrew M. Jones and Mark Burnley
Anni Vanhatalo, Andrew M. Jones, and Mark Burnley
The critical power (CP) is mathematically defined as the power-asymptote of the hyperbolic relationship between power output and time-to-exhaustion. Physiologically, the CP represents the boundary between the steady-state and nonsteady state exercise intensity domains and therefore may provide a more meaningful index of performance than other well-known landmarks of aerobic fitness such as the lactate threshold and the maximal O2 uptake. Despite the potential importance to sports performance, the CP is often misinterpreted as a purely mathematical construct which lacks physiological meaning and only in recent years has this concept begun to emerge as valid and useful technique for monitoring endurance fitness. This commentary defines the basic principles of the CP concept, outlines its importance to high-intensity exercise performance, and provides an overview of the current methods available for its assessment. Interventions including training, pacing and prior exercise can be used to alter the parameters of the power-time relationship. A future challenge lies in optimizing such interventions in order to positively affect the parameters of the power-time relationship and thereby enhance sports performance in specific events.
Melitta A. McNarry, Joanne R. Welsman, and Andrew M. Jones
The influence of training status on pulmonary VO2 recovery kinetics, and its interaction with maturity, has not been investigated in young girls. Sixteen prepubertal (Pre: trained (T, 11.4 ± 0.7 years), 8 untrained (UT, 11.5 ± 0.6 years)) and 8 pubertal (Pub: 8T, 14.2 ± 0.7 years; 8 UT, 14.5 ± 1.3 years) girls completed repeat transitions from heavy intensity exercise to a baseline of unloaded exercise, on both an upper and lower body ergometer. The VO2 recovery time constant was significantly shorter in the trained prepubertal and pubertal girls during both cycle (Pre: T, 26 ± 4 vs. UT, 32 ± 6; Pub: T, 28 ± 2 vs. UT, 35 ± 7 s; both p < .05) and upper body exercise (Pre: T, 26 ± 4 vs. UT, 35 ± 6; Pub: T, 30 ± 4 vs. UT, 42 ± 3 s; both p < .05). No interaction was evident between training status and maturity. These results demonstrate the sensitivity of VO2 recovery kinetics to training in young girls and challenge the notion of a “maturational threshold” in the influence of training status on the physiological responses to exercise and recovery.
Philip F. Skiba, David Clarke, Anni Vanhatalo, and Andrew M. Jones
Recently, an adaptation to the critical-power (CP) model was published, which permits the calculation of the balance of the work capacity available above the CP remaining (W′bal) at any time during intermittent exercise. As the model is now in use in both amateur and elite sport, the purpose of this investigation was to assess the validity of the W′bal model in the field. Data were collected from the bicycle power meters of 8 trained triathletes. W′bal was calculated and compared between files where subjects reported becoming prematurely exhausted during training or competition and files where the athletes successfully completed a difficult assigned task or race without becoming exhausted. Calculated W′bal was significantly different between the 2 conditions (P < .0001). The mean W′bal at exhaustion was 0.5 ± 1.3 kJ (95% CI = 0–0.9 kJ), whereas the minimum W′bal in the nonexhausted condition was 3.6 ± 2.0 kJ (95% CI = 2.1–4.0 kJ). Receiver-operator-characteristic (ROC) curve analysis indicated that the W′bal model is useful for identifying the point at which athletes are in danger of becoming exhausted (area under the ROC curve = .914, SE .05, 95% CI .82–1.0, P < .0001). The W′bal model may therefore represent a useful new development in assessing athlete fatigue state during training and racing.
Louise M. Burke, Asker E. Jeukendrup, Andrew M. Jones, and Martin Mooses
Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large fraction of this power, and high running/walking economy. Nutrition-related contributors include body mass and anthropometry, capacity to use fuels, particularly carbohydrate (CHO) to produce adenosine triphosphate economically over the duration of the event, and maintenance of reasonable hydration status in the face of sweat losses induced by exercise intensity and the environment. Race nutrition strategies include CHO-rich eating in the hours per days prior to the event to store glycogen in amounts sufficient for event fuel needs, and in some cases, in-race consumption of CHO and fluid to offset event losses. Beneficial CHO intakes range from small amounts, including mouth rinsing, in the case of shorter events to high rates of intake (75–90 g/hr) in the longest races. A personalized and practiced race nutrition plan should balance the benefits of fluid and CHO consumed within practical opportunities, against the time, cost, and risk of gut discomfort. In hot environments, prerace hyperhydration or cooling strategies may provide a small but useful offset to the accrued thermal challenge and fluid deficit. Sports foods (drinks, gels, etc.) may assist in meeting training/race nutrition plans, with caffeine, and, perhaps nitrate being used as evidence-based performance supplements.
Stephen J. Bailey, Anni Vanhatalo, Matthew I. Black, Fred J. DiMenna, and Andrew M. Jones
To assess whether combining prior “priming” exercise with an all-out pacing strategy is more effective at improving oxygen-uptake (V̇O2) kinetics and cycling performance than either intervention administered independently.
Nine men completed target-work cycling performance trials using a self-paced or all-out pacing strategy with or without prior severe-intensity (70%Δ) priming exercise. Breath-by-breath pulmonary V̇O2 and cycling power output were measured during all trials.
Compared with the self-paced unprimed control trial (22 ± 5 s), the V̇O2 mean response time (MRT) was shorter (V̇O2 kinetics were faster) with all-out pacing (17 ± 4 s) and priming (17 ± 3 s), with the lowest V̇O2 MRT observed when all-out pacing and priming were combined (15 ± 4 s) (P < .05). However, total O2 consumed and end-exercise V̇O2 were only higher than the control condition in the primed trials (P < .05). Similarly, cycling performance was improved compared with control (98 ± 11 s) in the self-paced primed (93 ± 8 s) and all-out primed (92 ± 8 s) trials (P < .05) but not the all-out unprimed trial (97 ± 5 s; P > .05).
These findings suggest that combining an all-out start with severe-intensity priming exercise additively improves V̇O2 MRT but not total O2 consumption and cycling performance since these were improved by a similar magnitude in both primed trials relative to the self-paced unprimed control condition. Therefore, these results support the use of priming exercise as a precompetition intervention to improve oxidative metabolism and performance during short-duration high-intensity cycling exercise, independent of the pacing strategy adopted.
Marc V. Jones, Andrew M. Lane, Steven R. Bray, Mark Uphill, and James Catlin
The present paper outlines the development of a sport-specific measure of precompetitive emotion to assess anger, anxiety, dejection, excitement, and happiness. Face, content, factorial, and concurrent validity were examined over four stages. Stage 1 had 264 athletes complete an open-ended questionnaire to identify emotions experienced in sport. The item pool was extended through the inclusion of additional items taken from the literature. In Stage 2 a total of 148 athletes verified the item pool while a separate sample of 49 athletes indicated the extent to which items were representative of the emotions anger, anxiety, dejection, excitement, and happiness. Stage 3 had 518 athletes complete a provisional Sport Emotion Questionnaire (SEQ) before competition. Confirmatory factor analysis indicated that a 22-item and 5-fac-tor structure provided acceptable model fit. Results from Stage 4 supported the criterion validity of the SEQ. The SEQ is proposed as a valid measure of precompetitive emotion for use in sport settings.
Stephen A. Ingham, Barry W. Fudge, Jamie S. Pringle, and Andrew M. Jones
Prior high-intensity exercise increases the oxidative energy contribution to subsequent exercise and may enhance exercise tolerance. The potential impact of a high-intensity warm-up on competitive performance, however, has not been investigated.
To test the hypothesis that a high-intensity warm-up would speed VO2 kinetics and enhance 800-m running performance in well-trained athletes.
Eleven highly trained middle-distance runners completed two 800-m time trials on separate days on an indoor track, preceded by 2 different warm-up procedures. The 800-m time trials were preceded by a 10-min self-paced jog and standardized mobility drills, followed by either 6 × 50-m strides (control [CON]) or 2 × 50-m strides and a continuous high-intensity 200-m run (HWU) at race pace. Blood [La] was measured before the time trials, and VO2 was measured breath by breath throughout exercise.
800-m time-trial performance was significantly faster after HWU (124.5 ± 8.3 vs CON, 125.7 ± 8.7 s, P < .05). Blood [La] was greater after HWU (3.6 ± 1.9 vs CON, 1.7 ± 0.8 mM; P < .01). The mean response time for VO2 was not different between conditions (HWU, 27 ± 6 vs CON, 28 ± 7 s), but total O2 consumed (HWU, 119 ± 18 vs CON, 109 ± 28 ml/kg, P = .05) and peak VO2 attained (HWU, 4.21 ± 0.85 vs CON, 3.91 ± 0.63 L/min; P = .08) tended to be greater after HWU.
These data indicate that a sustained high-intensity warm-up enhances 800-m time-trial performance in trained athletes.
Matthew W. Hoon, Andrew M. Jones, Nathan A. Johnson, Jamie R. Blackwell, Elizabeth M. Broad, Bronwen Lundy, Anthony J. Rice, and Louise M. Burke
Beetroot juice is a naturally rich source of inorganic nitrate (NO3 −), a compound hypothesized to enhance endurance performance by improving exercise efficiency.
To investigate the effect of different doses of beetroot juice on 2000-m ergometer-rowing performance in highly trained athletes.
Ten highly trained male rowers volunteered to participate in a placebo-controlled, double-blinded crossover study. Two hours before undertaking a 2000-m rowing-ergometer test, subjects consumed beetroot juice containing 0 mmol (placebo), 4.2 mmol (SINGLE), or 8.4 mmol (DOUBLE) NO3 −. Blood samples were taken before supplement ingestion and immediately before the rowing test for analysis of plasma [NO3 −] and [nitrite (NO2 −)].
The SINGLE dose demonstrated a trivial effect on time to complete 2000 m compared with placebo (mean difference: 0.2 ± 2.5 s). A possibly beneficial effect was found with DOUBLE compared with SINGLE (mean difference –1.8 ± 2.1 s) and with placebo (–1.6 ± 1.6 s). Plasma [NO2 −] and [NO3 −] demonstrated a dose-response effect, with greater amounts of ingested nitrate leading to substantially higher concentrations (DOUBLE > SINGLE > placebo). There was a moderate but insignificant correlation (r = –.593, P = .055) between change in plasma [NO2 −] and performance time.
Compared with nitratedepleted beetroot juice, a high (8.4 mmol NO3 −) but not moderate (4.2 mmol NO3 −) dose of NO3 − in beetroot juice, consumed 2 h before exercise, may improve 2000-m rowing performance in highly trained athletes.
Yu-Tzu Wu, Natalia R. Jones, Esther M.F. van Sluijs, Simon J. Griffin, Nicholas J. Wareham, and Andrew P. Jones
We examine the relative importance of both objective and perceived environmental features for physical activity in older English adults. Self-reported physical activity levels of 8,281 older adults were used to compute volumes of outdoor recreational and commuting activity. Perceptions of neighborhood environment supportiveness were drawn from a questionnaire survey and a geographical information system was used to derive objective measures. Negative binominal regression models were fitted to examine associations. Perceptions of neighborhood environment were more associated with outdoor recreational activity (over 10% change per standard deviation) than objective measures (5–8% change). Commuting activity was associated with several objective measures (up to 16% change). We identified different environmental determinants of recreational and commuting activity in older adults. Perceptions of environmental supportiveness for recreational activity appear more important than actual neighborhood characteristics. Understanding how older people perceive neighborhoods might be key to encouraging outdoor recreational activity.