The physiological effects of cycling on tandem and single bicycles.

OBJECTIVE: The purpose of this field study was to compare the physiological responses from cycling on a tandem road bicycle to those from cycling on a single road bicycle. METHODS: Nine pairs of experienced, recreational tandem cyclists rode a tandem or their single bicycle for 5 min at each velocity of 19.3, 22.5, 25.8, and 29.0 kph on a flat, paved surface. Heart rate (HR), rating of perceived exertion (RPE), and lactic acid (LA) data were collected after each interval. RESULTS: Riding a tandem resulted in lower HR, RPE, and LA mean values across the four velocities compared to the single bicycle. Mean (SD) HR, RPE, and LA for tandem and single bicycles were 126 (20.7) v 142 (20.1) bpm, 10.1 (1.7) v 11.3 (2.6), and 1.46 (1.0) mM/L v 2.36 (1.7) mM/L, respectively. No position differences were observed between the captain and stoker (front and rear positions) when both were on the tandem. Stokers had significantly lower HR, LA, and RPE values when they rode a tandem compared to a single bicycle. No statistical differences were observed between bicycles for the captains. When on the single bicycle, captains exhibited significantly lower HR, RPE, and LA values than stokers. CONCLUSION: Cycling on a tandem resulted in lower physiological stress than when cycling at the same velocity on a single bicycle. Cyclists were able to ride from 4.8-8.0 kph faster on a tandem than on a single bicycle at similar physiological stress. Apparently, stokers can add to power output on a tandem without adding significantly to wind resistance.

The effects of breathing supplemental oxygen during altitude training on cycling performance.

To compare the training effects of doing high intensity intervals at 1,840 m in a normoxic vs. hyperoxic environment, eight cyclists (NORM) performed intervals on ergometers 3d/wk while breathing normoxic gas (P1O2 = 128 Torr), and seven subjects (HYPER) performed identical intervals at the same relative workload while breathing hyperoxic gas (P1O2 = 156 Torr). HYPER subjects were able to train at a higher percentage of their altitude lactate inflection point than were NORM subjects (HYPER = 126+/-2%, NORM = 109+/-3% p<0.05). Improvements in power output at maximal steady state (NORM = 8 W, HYPER = 20 W,) and improvement in time to complete a 120 kJ cycling performance test (NORM = 2 s, HYPER = 15 s) were significant in the HYPER group pre- vs. post-training (p<0.05) while the NORM group exhibited no significant changes. No significant changes in power output at lactate inflection point were seen in either group (NORM = -12 W, HYPER = +11 W). The results demonstrate that while training at moderate altitude, breathing hyperoxic gas vs. ambient air allows for higher training intensities and this higher intensity training results in significant improvements in maximal steady state power output and time to complete a 120 kJ performance test.

Comparing cycling world hour records, 1967-1996: modeling with empirical data.

PURPOSE: The world hour record in cycling has increased dramatically in recent years. The present study was designed to compare the performances of former/current record holders, after adjusting for differences in aerodynamic equipment and altitude. Additionally, we sought to determine the ideal elevation for future hour record attempts. METHODS: The first step was constructing a mathematical model to predict power requirements of track cycling. The model was based on empirical data from wind-tunnel tests, the relationship of body size to frontal surface area, and field power measurements using a crank dynamometer (SRM). The model agreed reasonably well with actual measurements of power output on elite cyclists. Subsequently, the effects of altitude on maximal aerobic power were estimated from published research studies of elite athletes. This information was combined with the power requirement equation to predict what each cyclist's power output would have been at sea level. This allowed us to estimate the distance that each rider could have covered using state-of-the-art equipment at sea level. According to these calculations, when racing under equivalent conditions, Rominger would be first, Boardman second, Merckx third, and Indurain fourth. In addition, about 60% of the increase in hour record distances since Bracke's record (1967) have come from advances in technology and 40% from physiological improvements. RESULTS AND CONCLUSIONS: To break the current world hour record, field measurements and the model indicate that a cyclist would have to deliver over 440 W for 1 h at sea level, or correspondingly less at altitude. The optimal elevation for future hour record attempts is predicted to be about 2500 m for acclimatized riders and 2000 m for unacclimatized riders.

Racing cyclist power requirements in the 4000-m individual and team pursuits.

PURPOSE: The purpose of this paper is: 1) to present field test data describing the power requirements of internationally competitive individual and team pursuiters, and 2) to develop a theoretical model for pursuit power based upon on these tests. METHODS: In preparing U.S. cycling's pursuit team for the 1996 Atlanta Olympics, U.S. team scientists measured cycling power of seven subjects on the Atlanta track using a crank dynamometer (SRM) at speeds from 57 to 60 kph. By using these field data and other tests, mathematical models were devised which predict both individual and team pursuit performance. The field data indicate the power within a pace line at 60 kph averages 607 W in lead position (100%), 430 W in second position (70.8%), 389 W in third position (64.1%), and 389 W in fourth position (64.0%). A team member requires about 75% of the energy necessary for cyclists riding alone at the same speed. These results compare well with field measurements from a British pursuit team, to recent wind tunnel tests, and to earlier bicycle coast down tests. RESULTS: The theoretical models predict performance with reasonable accuracy when the average power potential of an individual or team is known, or they may be used to estimate the power of pursuit competitors knowing race times. The model estimates that Christopher Boardman averaged about 520 W when setting his 1996, 4000-m individual pursuit record of 4 min 11.114 s and the Italian 4000-m pursuit team averaged about 480 W in setting their record of 4:00.958. Both used the "Superman" cycling position. CONCLUSIONS: These records would be very difficult to break using less aerodynamic riding positions, due to the extraordinarily high power requirements.

De incidentie van primaire maligne bottumoren in Suriname / The incidence of primary malignant bone tumors in Suriname

In a retrospective research the incidence of primary malignant bone tumors in Suriname is recorded. In the period 1978 up to and including 1987 there were 15 patients with primary malignant bone tumors, 9 men and 6 women. The incidence is o.4 per 100.000 per year and for men and women 0.5 and 0.3 respectively.It may be concluded that with the occurence of 1 to 2 cases per year, these primary bone tumor are rare in Suriname.....a.o

The incidence of primary malignant bone tumors in Suriname

In a retrospective research the incidence of primary malignant bone tumors in Suriname is recorded. In the period 1978 up to and including 1987 there were 15 patients with primary malignant bone tumors, 9 men and 6 women. The incidence is 0.4 per 100.000 per year and for men and women 0.5 and 0.3 respectively. It may be concluded that with the occurrence of 1 to 2 cases per year, these primary bone tumors are rare in Suriname......(AU)

The effects of mountain bike suspension systems on energy expenditure, physical exertion, and time trial performance during mountain bicycling.

The purpose of this 3-Phase study was to investigate the effects of suspension systems on muscular stress, energy expenditure, and time trial performance during mountain biking. Three suspension systems were tested, a rigid frame bike (RIG), a suspension fork bike (FS), and a front and rear suspension bike (FSR). Phase I and II consisted of cycling at 16.1 km.hr-1 over a flat, bumpy course for 63 min. Phase III consisted of ascending (ATT), descending (DTT), and cross country (XTT) time trials. Phase I assessed muscular stress by 24 h change in CK, Phase II assessed HR, VO2, VE, and Phase III assessed performance responses to the suspension systems. The 24 hr change in CK was greater for RIG than FS and FSR (+91.9 +/- 79.5 IU vs +8.6 +/- 17.5 IU and +9.7 +/- 21.8 IU). Mean HR was greater for RIG than FS and FSR (153.7 +/- 15.6 bpm vs 146.7 +/- 15.4 bpm, 146.3 +/- 16.2 bpm). Subjects rode significantly faster on FS than FSR and RIG during the XTT (30.9 +/- 2.0 min vs 32.3 +/- 3.6 min, 32.3 +/- 3.2 min). Subjects RPE was lower for FSR than FS and RIG, however, no differences were observed for VO2, VE, ATT, or DTT. Cyclists incurred less muscular stress, indicated by CK and HR, when riding the FS and FSR. Although the FS and FSR weigh from 0.7 to 2.2 kg more than RIG, no differences were observed for energy expenditure and that riding the FS in a XTT resulted in a faster finishing time than FSR or RIG.

Physiological responses to swimming while wearing a wet suit.

The purpose of this study was to examine the influence of three different wet suits on the oxygen uptake (VO(2)), minute ventilation (VE). and heart rate responses to front crawl swimming. Five male subjects swam at four velocities (0.90, 1.05, 1.18 +/- 0.01, 1.31 +/- 0.02 m.sec(-1)) in each of four swimming suit conditions in a swimming flume. Conditions were completed in random order using a conventional swimming suit (SS), a wet suit that covered the full body (FULL), a wet suit that left the arms exposed (LONG), and a wet suit that left the arms and lower legs exposed (SHORT). Water temperature was 26.5 +/- 1.0 degrees C for all trials. VO(2) and V(E) were decreased (p < 0.05) while swimming in the three wet suits as compared to the SS at all four velocities. VO(2) and V(E) were also lower (p < 0.05) in the FULL as compared to the SHORT at all four velocities; however, there were no differences between the SHORT and LONG or LONG and FULL at any of the velocities. Decreases in VO(2) from SS averaged 16.2 +/- 1.9 (SHORT), 22.8 +/- 2.4 (LONG), and 33.6 +/- 2.9% (FULL) over all four velocities. Similarly, reductions in V(E) from SS averaged 14.6+/- 1.5, 19.6 +/- 1.6, 24.2 +/- 1.5%, in the SHORT, LONG, and FULL, respectively. Heart rate and rating of perceived exertion were higher (p < 0.05) in the SS as compared to the three wet suits at 1.31 m.sec(-1) only. In conclusion, oxygen uptake and minute ventilation during swimming at a given velocity were decreased when wearing a wet suit as compared to a conventional swimming suit. Further, these decreases were related to the amount of wet suit covering the body.

The effects of albuterol on power output in non-asthmatic athletes.

The purpose of this study was to evaluate the effect of the beta 2-agonist albuterol (salbutamol) at twice the normal dosage (360 micrograms) on power output during a 30-second Wingate test and pulmonary function in highly trained cyclists (4 category 1 and 10 category II U.S.C.F. track cyclists). The cyclists did not have a history of exercise induced bronchial spasms, and a 5 step methacholine challenge confirmed all subjects to be non-asthmatic. The project was performed in a random block, double blind design. Twenty minutes before the 30-second Wingate cycle ergometer exercise, albuterol (90 micrograms per dose) or a saline placebo was administered by inhaler in 4 metered doses. Pulmonary function tests were performed at rest, 20 minutes post-inhalation, and 5, 10, 15 minutes post-exercise. After a standard warm-up, a 30-second Wingate anaerobic power test was performed on a cycle ergometer at a resistance of 0.10 kg (kg body mass)-1. Multi-variate ANOVA revealed no significant difference between the albuterol and placebo treatment for the anaerobic power measures: peak power (1,136.7 +/- 40.9 vs 1,124.8 +/- 39.8 W, mean +/- s.e.), total work (27,213.6 +/- 653.1 vs 27,093.3 +/- 677.4j), time to peak power (4.5 +/- 0.2 vs 4.8 +/- 0.5 s), and fatigue index (16.5 +/- 1.8 vs 16.6 +/- 1.8 W.s-1). Peak heart rate (181.6 +/- 3.7 vs 181.4 +/- 3.8 bpm), or blood lactate (14.0 +/- 0.9 vs 13.8 +/- 0.8 mmol.l-1) 3 min after the exercise bout were not significantly different between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium bicarbonate ingestion does not improve performance in women cyclists.

We hypothesized that oral ingestion of sodium bicarbonate (NaHCO3) would improve performance in seven competitive female cyclists VO2 = 51.6 +/- 4.8 ml.kg-1.min-1 at moderate altitude (2800 m). Two hours before exercise subjects ingested either NaHCO3 (300 mg.kg-1) or NaCl (207 mg.kg-1), both containing equimolar amounts of sodium. The exercise protocol consisted of repeated 1-min intervals at 95% VO2max (277 +/- 38 W) followed by 1 min of recovery at 60 W until exhaustion. Continuous cardiopulmonary physiologic variables and arterialized venous blood gases were measured. Maximum interval ventilation, heart rate, and VO2 did not differ between the two interventions, but pH was significantly higher before and throughout the NaHCO3 trial. pH values for NaHCO3 vs NaCl trials were 7.47 +/- 0.04 vs 7.40 +/- 0.03 prior to exercise and 7.32 +/- 0.08 vs 7.23 +/- 0.04 post-exercise (P < 0.01). The number of intervals completed with NaHCO3 (10.0 +/- 0.9) was not different from NaCl (8.4 +/- 0.9). The failure of bicarbonate to enhance performance at moderate altitude may be attributed to our controlling for the amount of sodium ingested. The intravascular volume expansion with NaHCO3 rather than the increase in blood buffer capacity may underlie the previously reported benefit of orally ingested bicarbonate in exercise performance.

Proper fit of the bicycle.

After cyclists have carefully made adjustments for proper fit, minor aches and pains may develop before the body adjusts to the new riding posture. This is normal--so resist the temptation to fiddle with the position much. They will become accustomed to the new riding position after a few rides, and cycling performance will be improved. Then they can concentrate on bike handling skills and fitness confident that their riding position is as good as can be. Proper bicycle fit requires careful review of bicycle selection, saddle height for proper leg extension, fore-and-aft positioning of the knee over the pedal, saddle tilt, handlebar position, and positioning of the upper body for optimum comfort and performance. Further research on the effects of maintaining an aerodynamic position for extended periods of time needs to be investigated to review fatigue patterns in lower and upper body musculature. The underlying principle of positioning a cyclist on a bicycle is to remember that the bicycle is adjustable, and the cyclist is adaptable.

Scientific, medical, and practical aspects of stretching.

This article addresses the medical, scientific, and practical aspects of stretching. Sections include information on the physiology of flexibility and stretching, stretching versus warm-up, and the clinical evaluation of flexibility. Detailed instructions for numerous stretching exercises for the major muscle groups are provided. Techniques for proper stretching are included.

Complications of stapled anastomoses in anterior resection for rectal carcinoma: colorectal anastomosis versus coloanal anastomosis.

Postoperative results of 48 patients who underwent anterior resection using the EEA-stapler were evaluated. In all but 2 cases the indication for surgery was colorectal carcinoma. In 24 patients an anastomosis was created above the 5 cm level (above the anal verge: colorectal anastomosis) and in 24 at the 0-5 cm level (coloanal anastomosis). There was no perioperative mortality. The only complication observed in the colorectal anastomosis group was one case of late anastomotic stenosis. In the coloanal anastomosis group there were 4 cases with early anastomosis leaks, 3 cases with late stenosis and 5 cases with various degrees of late fecal incontinence, ultimately resulting in a permanent diverting stoma in 5 (10.4%) patients. We conclude that for rectal tumors the EEA-stapled anterior resection provides excellent functional results in most cases. Stapled coloanal anastomoses more often demonstrate various (early and late) complications. Nevertheless in spite of chronic discomfort, many patients still prefer their complaints to a permanent stoma.

Failure to find residual memory deficits in monkeys after repeated HPNS.

Squirrel monkeys (n = 8) were equated on learning and memory tasks before sustaining 3 separate dives in a laboratory compression chamber. Associative memory was carefully monitored 1 wk before and 3 wk immediately after each dive. The first dive was a shallow, subseizure control dive and the subsequent 2 dives were deep, seizure-inducing dives. Half of the animals were always compressed in He-O2 and half in He-N2-O2 gas, which is known to increase the depth at which tremors and seizures occur. After the control dive there was a slight (10% average) decline in memory performance, but the decline was temporary and recovery was complete by the second postdive week. There was no evidence of residual memory impairments after either of the 2 subsequent seizure-inducing dives. Although addition of nitrogen to the breathing gas significantly elevated thresholds for tremors, it had no differential effect on memory scores. These results are in agreement with studies of human divers that show either no residual impairments or transient, fully recoverable cognitive symptoms after diving.

Safety Standards for Bicycle Helmets.

Head injuries are the leading cause of death among cyclists. By using helmets that meet safety standards, cyclists can minimize the damage that could occur during accidents.

Hematological Variations After Endurance Running With Hard-and Soft-Soled Running Shoes.

In brief: Blood measurements were taken in 23 marathon runners to investigate whether the hardness of the sole of the running shoe would affect RBC indexes. Runners were randomly assigned to a group with either a firm-sole running shoe or an air-cushion shoe. Measurements before and after the 15-mile run included complete blood count, serum haptoglobin, plasma hemoglobin, and venous hemoglobin. Runners wearing air-cushion shoes demonstrated smaller hematological effects after strenuous exercise than did runners wearing firm-sole shoes. This study indicates that (1) material property of the running shoes may be correlated with physiological measurements, and (2) appropriate cushioning in running shoes may reduce the RBC abnormalities experienced in long-distance running.