Alejandro F. San Juan

How Do Endurance Runners Actually Train? Relationship with Competition Performance

PURPOSE To quantify the relationship between total training load and running performance during the most important competitions of the season (national cross-country championships, 4.175- and 10.130-km races). METHODS Eight well-trained, subelite endurance runners (age (mean+/-SD): 23+/-2 yr; VO2max: 70.0+/-7.3 mL.kg.min) performed a maximal cardiorespiratory exercise test before the training period to determine ventilatory threshold (VT) and respiratory compensation threshold (RCT). Heart rate was continuously recorded using telemetry during each training session over a 6-month macrocycle, designed to achieve peak performance during the aforementioned cross-country races, lasting from late August to the time that these races were held, that is, mid-February. This allowed us to quantify the total cumulative time spent in three intensity zones calculated as zone 1 (low intensity, lower than the VT); zone 2 (moderate intensity, between VT and RCT); and zone 3 (high intensity, above the RCT). RESULTS Total training time in zone 1 (4581+/-979 min) was significantly higher (P<0.001) than that accumulated in zones 2 (1354+/-583 min) and 3 (487+/-154 min). Total time in zone 2 was significantly higher than time in zone 3 (P<0.05). A correlation coefficient of r=-0.79 (P=0.06) and r=-0.97 (P=0.008) was found between the total training time spent in zone 1 and performance time during the short and long cross-country races, respectively. CONCLUSIONS Our findings suggest that total training time spent at low intensities might be associated with improved performance during highly intense endurance events, especially if the event duration is approximately 35 min. Interventional studies (i.e., improving or reducing training time in zone 1) are needed to corroborate our findings and to elucidate the physiological mechanisms behind them.

In professional road cyclists, low pedaling cadences are less efficient.

PURPOSE To determine the effects of changes in pedaling frequency on the gross efficiency (GE) and other physiological variables (oxygen uptake (VO2), HR, lactate, pH, ventilation, motor unit recruitment estimated by EMG) of professional cyclists while generating high power outputs (PO). METHODS Following a counterbalanced, cross-over design, eight professional cyclists (age (mean +/- SD): 26 +/- 2 yr, VO2max: 74.0 +/- 5.7 mL x kg x min) performed three 6-min bouts at a fixed PO (mean of 366 +/- 37 W) and at a cadence of 60, 80, and 100 rpm. RESULTS Values of GE averaged 22.4 +/- 1.7, 23.6 +/- 1.8 and 24.2 +/- 2.0% at 60, 80, and 100 rpm, respectively. Mean GE at 100 rpm was significantly higher than at 60 rpm (P < 0.05). Similarly, mean values of VO2, HR, rates of perceived exertion (RPE), lactate and normalized root-mean square EMG (rms-EMG) in both vastus lateralis and gluteus maximum muscles decreased at increasing cadences. CONCLUSIONS In professional road cyclists riding at high PO, GE/economy improves at increasing pedaling cadences.

Physical Activity and Pediatric Cancer Survivorship

Owing to improved treatment pro-tocols in the last 25 years there have been dramatic improvements in the 5-year relative survival rate of the most prevalent childhood cancers. For instance, the 5-year relative survival rate among children for all cancer sites combined, improved from 58% to 80% in patients diagnosed in 1975-1977 and in 1996-2004 respectively. However, as survival rates have improved, there has been an increasing recognition of adverse short and longer term effects associated with treatment and cancer itself, which we describe in detail in this chapter. There is growing interest in those interventions that can counteract the adverse effects of treatment and cancer. Because such adverse effects are further aggravated by physical inactivity, a special emphasis is being placed on physical activity (PA) interventions. Results are promising: there is increasing evidence that regular PA can improve the overall health status, functional capacity, and quality of life (QOL) of children with cancer as well as of older survivors of childhood cancer.

Is Cardiorespiratory Fitness Related to Quality of Life in Survivors of Breast Cancer

The purpose of this study was to investigate whether indices of cardiorespiratory fitness are related to quality of life (QOL) in women survivors of breast cancer. Using the European Organization for Research and Treatment of Cancer QLQ-30 questionnaire, we assessed the QOL of 16 participants (age, 50 ± 9 years; body mass, 66.6 ± 9.6 kg). All participants performed incremental cycle ergometer exercise to determine several indices of cardio-respiratory fitness (e.g., peak oxygen uptake [&OV0312;O2peak, in L·min−1, ml·kg−1·min−1]), peak power output (PPO, in W), PPO/ body mass (W·kg−1), peak heart rate (HRpeak, b·min−1), peak ventilation (VEpeak), and &OV0312;O2 and heart rate (HR) at the ventilatory (VT) and respiratory compensation (RCT) thresholds. Relationships between QOL and variables were assessed using Spearman rank-difference correlation tests. A significant inverse relationship (p < 0.05) was found for QOL scores and values for age (years) and body mass (kg) (ρ = −0.53), %HRpeak@VT (ρ = −0.59) and %VEpeak@VT (ρ = −0.61). A significant positive relationship (p < 0.05) was found for QOL and PPO/body mass (ρ =0.59) and HRpeak (ρ = 0.78), &OV0312;O2@RCT (ml·kg−1·min−1)(ρ = 0.51), power output (PO, expressed as either W or W·kg−1) at RCT, and HR at RCT (ρ = 0.54). No other significant relationship was found between QOL and variables obtained from the tests. In conclusion, these findings highlight possible relationships between cardiorespiratory fitness and well-being in survivors of breast cancer. From a practical point of view, our data emphasize the need for this population to engage in programmed cardiorespiratory exercise training, mainly designed to improve VT and RCT. The improvement of both submaximal indices can have a beneficial effect on QOL.

Does creatine supplementation improve functional capacity in elderly women

The purpose of this study was to determine the effects of shortterm (7 days) oral creatine supplementation (0.3 g·kg−1) in elderly women during exercise tests that reflect functional capacity during daily living tasks. We assessed several indices of endurance capacity (1-mile walk test, gross mechanical efficiency, ventilatory threshold, and peak oxygen intake determined during cycle-ergometry) and lower-extremity functional performance (time to complete sit-stand test). Subjects were assigned to a creatine (n = 10; age 67 ± 6 years) or placebo (n = 6; age 68 ± 4 years) group. We found a significant improvement only after creatine loading in the sit-stand test (placebo: 9.7 ± 0.9 seconds for pretest and 9.3 ± 0.7 seconds for posttest, p > 0.05; creatine: 10.0 ± 0.7 seconds for pretest and 8.8 ± 1.1 seconds for posttest). Significance was recorded at p < 0.05 for the interaction effect (group [creatine, placebo] 3 time [pretest, post-test]). In elderly women, short-term oral creatine supplementation does not improve endurance capacity but increases the ability to perform lower-body functional living tasks involving rapid movements.

Xanthine Oxidase Pathway and Muscle Damage. Insights from McArdle Disease

The intent of this article is to summarize current body of knowledge on the potential implication of the xanthine oxidase pathway (XO) on skeletal muscle damage. The possible involvement of the XO pathway in muscle damage is exemplified by the role of XO inhibitors (e.g., allopurinol) in attenuating muscle damage. Reliance on this pathway (as well as on the purine nucleotide cycle) could be exacerbated in conditions of low muscle glycogen availability. Thus, we also summarize current hypotheses on the etiology of both baseline and exertional muscle damage in McArdle disease, a condition caused by inherited deficiency of myophosphorylase. Because myophosphorylase catalyzes the first step of muscle glycogen breakdown, patients are unable to obtain energy from their muscle glycogen stores. Finally, we provide preliminary data from our laboratory on the potential implication of the XO pathway in the muscle damage that is commonly experienced by these patients.

C34T mutation of the AMPD1 gene in an elite white runner.

The case is reported of an elite, male, white endurance runner (28 years of age), who is one of the best non-African runners in the world despite carrying the C34T mutation in the gene (AMPD1) that encodes the skeletal muscle specific isoform of AMP deaminase, an enzyme important in muscle metabolism. The frequency of the mutant allele in sedentary white people is 8–11%. Previous research has shown that this mutation, at least in homozygotes, can impair the exercise capacity of untrained people and their trainability. The maximum oxygen uptake (VO2MAX) of the study subject was exceptionally high (83.6 mlO2/kg/min), whereas his ammonia and lactate concentrations at high submaximal running speeds were lower than those of other world class runners who are not carriers of the mutation. The partial metabolic deficiency of the study subject is possibly compensated for by his exceptionally favourable anthropometric characteristics (body mass index 18.2 kg/m2).