Single-leg cycling to maintain and improve function in healthy and clinical populations.

Exercise with reduced muscle mass facilitates greater muscle-specific adaptations than training with larger muscle mass. The smaller active muscle mass can demand a greater portion of cardiac output which allows muscle(s) to perform greater work and subsequently elicit robust physiological adaptations that improve health and fitness. One reduced active muscle mass exercise that can promote greater positive physiological adaptations is single-leg cycling (SLC). Specifically, SLC confines the cycling exercise to a smaller muscle mass resulting in greater limb specific blood flow (i.e., blood flow is no longer "shared" by both legs) which allows the individual to exercise at a greater limb specific intensity or for a longer duration. Numerous reports describing the use of SLC have established cardiovascular and/or metabolic benefits of this exercise modality for healthy adults, athletes, and individuals living with chronic diseases. SLC has served as a valuable research tool for understanding central and peripheral factors to phenomena such as oxygen uptake and exercise tolerance (i.e., V̇O2peak and V̇O2 slow component). Together, these examples highlight the breadth of applications of SLC to promote, maintain, and study health. Accordingly, the purpose of this review was to describe: 1) acute physiological responses to SLC, 2) long-term adaptations to SLC in populations ranging from endurance athletes to middle aged adults, to individuals living with chronic disease (COPD, heart failure, organ transplant), and 3) various methods utilized to safely perform SLC. A discussion is also included on clinical application and exercise prescription of SLC for the maintenance and/or improvement of health.

Mechanisms that underlie blood flow regulation at rest and during exercise.

The cardiovascular system must distribute oxygen and nutrients to the body while maintaining appropriate blood pressure. This is achieved through a combination of central and peripheral mechanisms that influence cardiac output and vasomotor tone throughout the vascular system. Furthermore, the capability to preferentially direct blood to tissues with increased metabolic demand (i.e., active hyperemia) is crucial to exercise tolerance. However, the interaction between these systems is difficult to understand without real-life examples. Fortunately, monitoring blood flow, blood pressure, and heart rate during a series of laboratory protocols will allow students to partition the contributions of these central and peripheral factors. The three protocols include 1) reactive hyperemia in the forearm, 2) small muscle mass handgrip exercise, and 3) large muscle mass cycling exercise. In addition to providing a detailed description of the required equipment, specific protocols, and expected outcomes, this report also reviews some of the common student misconceptions that are associated with the observed physiological responses.NEW & NOTEWORTHY Blood flow regulation during exercise is a complicated process that involves many overlapping mechanisms. This laboratory will help students better understand how the body regulates blood flow to the active muscles using three separate protocols: 1) reactive hyperemia, 2) small muscle mass exercise, and 3) large muscle mass exercise.

Effect of maturation on parasympathetic modulation during exercise and recovery.

OBJECTIVES: This study examined the effect of maturation on parasympathetic nervous system (PNS) response from rest to light- to moderate-intensity exercise and recovery from maximal exercise in pre- (n = 10; maturity offset = -3.0 ± 1.2 years; age = 10.1 ± 1.9 years), mid- (n = 9; maturity offset = -0.1 ± 0.6 years; age = 13.7 ± 1.0 years), and postpubertal (n = 10; maturity offset = 1.9 ± 0.6 years; age = 15.6 ± 1.2 years) boys and men (n = 10; age = 24.1 ± 2.0 years). DESIGN: Participants completed seated rest, light-intensity exercise (50% HRmax), and moderate-intensity exercise (65% HRmax). Following moderate-intensity exercise, intensity was ramped to elicit maximal HR and followed by 25 min of seated recovery. Log transformed values for root mean square of successive differences (lnRMSSD), high-frequency power (lnHF) and normalized HF power (lnHFnu) assessed PNS modulation during 3 min of rest, light-intensity exercise, moderate-intensity exercise, and 3-min epochs throughout recovery. RESULTS: During light-intensity exercise, lnRMSSD and lnHF were greater in prepubertal (lnRMSSD = 3.4 ± 0.3 ms; lnHF = 5.4 ± 0.7 ms2) compared to men (lnRMSSD = 2.8 ± 0.5 ms; lnHF = 4.0 ± 0.9 ms2). During moderate-intensity exercise, lnHF differed between prepubertal and men (2.8 ± 1.0 vs. 1.4 ± 1.0 ms2). During recovery, HRV variables were greater in prepubertal compared to postpubertal and men. CONCLUSIONS: Prepubertal boys have reduced PNS withdrawal during light-intensity exercise and greater PNS reactivation following exercise.

Carbohydrate Drink Use During 30 Minutes of Variable-Intensity Exercise Has No Effect on Exercise Performance in Premenarchal Girls.

PURPOSE: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. METHODS: A total of 10 girls (10.4 [0.7] y) participated in the study. VO2peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO2peak and maximal sprints) before a 1-minute performance sprint. RESULTS: The mean power, peak power, heart rate (HR), %HRpeak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HRpeak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). CONCLUSION: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

Physiological Responses to Counterweighted Single-Leg Cycling in Older Males.

Single-leg cycling (SLC) allows for a greater muscle specific exercise capacity and therefore provides a greater stimulus for metabolic and vascular adaptations compared to double-leg cycling (DLC). The purpose of this investigation was to compare the cardiovascular, peripheral, and metabolic responses of counterweighted (10kg) SLC to DLC in a healthy older male population. Eleven males (56-86 years) performed two cycling modalities consisting of DLC and SLC. For each modality, participants performed 4-minute cycling trials (60rpm) at three work rates (25, 50, 75W). Repeated measures ANOVAs and paired samples T-test (α=0.05) were used to assess differences in physiological and perceptual responses. Heart rate (100±21 vs. 103±20bpm), oxygen uptake (12.1±3.6 vs. 11.7±2.8mL*kg-1*min-1) and mean arterial pressure (104±13 vs. 108±12mmHg) were not different between DLC and SLC, respectively. Femoral blood flow was greater during SLC at 50W (741.4±290.3 vs. 509.0±230.8mL/min) and 75W (993.8±236.2 vs. 680.6±278.0mL/min) (p≤0.01). Furthermore, carbohydrate oxidation during SLC was 30-40% greater than DLC across work rates (p≤0.011). Whole body rating of perceived exertion (RPE) at 25 and 50W were not different (p=0.065), however, whole body RPE at 75W and leg RPE were higher for SLC at all intensities (p≤0.018). Liking scores were not different between cycling modalities (p=0.060). At low and moderate intensities, SLC provides a greater peripheral stress with no difference in cardiovascular responses compared to DLC in a healthy older adult male population. Thus, SLC may be a feasible exercise modality to maximize peripheral adaptations for healthy and diseased (i.e. peripheral vascular disease/cardiovascular disease) older population.

The impact of REACH on classification for human health hazards.

The REACH Regulation represents a major piece of chemical legislation in the EU and requires manufacturers and importers of chemicals to assess the safety of their substances. The classification of substances for their hazards is one of the crucial elements in this process. We analysed the effect of REACH on classification for human health endpoints by comparing information from REACH registration dossiers with legally binding, harmonised classifications. The analysis included 142 chemicals produced at very high tonnages in the EU, the majority of which have already been assessed in the past. Of 20 substances lacking a harmonised classification, 12 chemicals were classified in REACH registration dossiers. More importantly, 37 substances with harmonised classifications for human health endpoints had stricter classifications in registration dossiers and 29 of these were classified for at least one additional endpoint not covered by the harmonised classification. Substance-specific analyses suggest that one third of these additional endpoints emerged from experimental studies performed to fulfil information requirements under REACH, while two thirds resulted from a new assessment of pre-REACH studies. We conclude that REACH leads to an improved hazard characterisation even for substances with a potentially good data basis.

Laparoscopic versus open radical nephrectomy: a 9-year experience.

PURPOSE: The laparoscopic approach for renal cell carcinoma is slowly evolving. We report our experience with laparoscopic radical nephrectomy and compare it to a contemporary cohort of patients with renal cell carcinoma who underwent open radical nephrectomy. MATERIALS AND METHODS: From 1990 to 1999, 32 males and 28 females underwent 61 laparoscopic radical nephrectomies for suspicious renal cell carcinoma. Clinical data from a computerized database were reviewed and compared to a contemporary group of 33 patients who underwent open radical nephrectomy for renal cell carcinoma. RESULTS: Patients in the laparoscopic radical nephrectomy group had significantly reduced, estimated blood loss (172 versus 451 ml., p <0.001), hospital stay (3.4 versus 5.2 days, p <0.001), pain medication requirement (28.0 versus 78.3 mg., p <0.001) and quicker return to normal activity than patients in the open radical nephrectomy group (3.6 versus 8.1 weeks, p <0.001). The majority of laparoscopic specimens (65%) were morcellated. Operating time and cost were higher in the laparoscopic than the open nephrectomy group. Average followup was 25 months (range 3 to 73) for the laparoscopic and 27.5 months (range 7 to 90) for the open group. Renal cell carcinoma in 3 patients (8%) recurred in the laparoscopic group versus renal cell carcinoma in 3 (9%) in the open group. When stratified patients with tumors larger than 4 to 10 cm. experienced similar benefits and results as patients with tumors less than or equal to 4 cm. To date there have been no instances of trocar or intraperitoneal seeding in the laparoscopic radical nephrectomy group. CONCLUSIONS: Laparoscopic radical nephrectomy, although technically demanding, is a viable alternative for managing localized renal tumors up to 10 cm. It affords patients with renal tumors an improved postoperative course with less pain and a quicker recovery while providing similar efficacy at 2-year followup for patients with T1 and T2 tumors.

Laparoscopic bladder neck suspension fails the test of time.

PURPOSE: Initial reports on laparoscopic bladder neck suspension have suggested success rates similar to those of traditional bladder neck suspension. We compare long-term success rates of laparoscopic and transvaginal Raz bladder neck suspension. MATERIALS AND METHODS: A total of 100 patients with anatomical stress urinary incontinence underwent extraperitoneal laparoscopic bladder neck suspension with securing of the endopelvic fascia to Cooper's ligament (58, laparoscopy group) or transvaginal Raz bladder neck suspension (42, transvaginal group). Patients were evaluated by chart review and telephone questionnaire to determine whether they had urinary incontinence. RESULTS: The 2 groups were similar in terms of age, mean body mass index, preoperative bladder capacity and post-void residual. Mean followup was 45 months (range 14 to 71) in 50 laparoscopy group (86%) and 59 months (range 35 to 72) in 29 transvaginal group (70%) patients. Only 15 of 50 laparoscopy group (30%) and 10 of 29 transvaginal group (35%) patients were completely continent at followup. There was no statistically significant difference in the success rates for the 2 groups. Mean time to failure for both groups was 18 to 24 months. CONCLUSIONS: With long-term followup laparoscopic bladder neck suspension demonstrated poor success rates similar to other minimally invasive surgical therapies for stress urinary incontinence. Any new surgical technique for treatment of stress urinary incontinence should have a mean followup of more than 2 years to determine true clinical efficacy.