Context: The combined effect of neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) on muscle mass and strength has not been thoroughly investigated. Objective: To examine the effects of combined and independent BFR and a low-intensity NMES on skeletal muscle adaptation. Design: Exploratory study. Setting: Laboratory. Participants: Twenty recreationally active subjects. Main Outcome Measures: Subjects had each leg randomly allocated to 1 of 4 possible intervention groups: (1) cyclic BFR alone, (2) NMES alone, (3) BFR + NMES, or (4) control. Each leg was stimulated in its respective intervention group for 32 minutes, 4 days per week for 6 weeks. Mean differences in size (in grams) and isometric strength (in kilograms), between week 0 and week 6, were calculated for each group. Results: Leg strength increased 32 (19) kg in the BFR + NMES group, which differed from the 3 (11) kg change in the control group (P = .03). The isolated NMES and BFR groups revealed increases of 16 (28) kg and 18 (17) kg, respectively, but these did not statistically differ from the control, or one another. No alterations were statistically significant for leg size. Conclusion: Compared with a control that received no treatment, the novel combination of BFR and NMES led to increasing muscular strength of the knee extensors, but not muscle mass which had a large interindividual variability in response.
Joshua T. Slysz and Jamie F. Burr
Tania Pereira, John Durocher and Jamie Burr
Background: Insufficient physical activity (PA) is associated with numerous chronic diseases and premature mortality, and the challenge of meeting recommended PA guidelines is exacerbated in the winter. Snowmobiling can potentially contribute to PA accumulation, but the objective metabolic and physical demands are unclear. The purpose of this study was to assess the physical demands of riding a snowmobile. Methods: Habitual snowmobile riders responded to a survey describing a typical ride (n = 4015). Using this data, terrain-specific testing courses were created, and recreational snowmobile riders (n = 40) participated in a scaled representative ride (21  min) while aerobic metabolism (VO2) and muscular fatigue were quantified. Results: The mean VO2 while riding, irrespective of terrain, was 18.5 (8.4) mL·kg−1·min−1, with significant differences based on geographic location (13.4 [5.2] vs 25.7 [6.6] mL·kg−1·min−1, P < .001). Muscular fatigue was apparent in maximal handgrip (−7% [8%], P < .001) across both riding terrains, but not lower body power, suggesting a greater influence of an upper body strength component. Conclusions: Snowmobiling is an activity that generally falls within the moderate-intensity activity range and involves both aerobic fitness and muscular strength. There were substantial differences in demand between terrains, suggesting that additional benefits may be conferred from mountain riding as it was more metabolically demanding.
Christian P. Cheung, Joshua T. Slysz and Jamie F. Burr
Ischemic preconditioning (IPC) through purposeful circulatory occlusion may enhance exercise performance. The value of IPC for improving performance is controversial owing to challenges with employing effective placebo controls. This study examines the efficacy of IPC vs a deceptive sham protocol for improving performance to determine whether benefits of IPC are attributable to true physiological effects. It was hypothesized that IPC would favorably alter performance more than a sham treatment and that physiological responses to exercise would be affected only after IPC treatment.
In a randomized order, 16 participants performed incremental exercise to exhaustion on a cycle ergometer in control conditions and after sham and IPC treatments. Participants rated their belief as to the efficacy of each treatment compared with control.
TTE was greatest after IPC (control 1331 ± 270 s, IPC 1429 ± 300 s, sham 1343 ± 255 s, P = .02,) despite negative performance expectations after IPC and positive expectation after sham. Maximal aerobic power remained unchanged after both SHAM and IPC (control 42.0 ± 5.2, IPC 41.7 ± 5.5, sham 41.6 ± 5.5 mL·kg-1·min-1, P = .7), as did submaximal lactate concentration (control 8.9 ± 2.6, sham 8.0 ± 1.9, IPC 7.7 ± 2.1 mmol, P = .1) and oxygen uptake (control 37.8 ± 4.8, sham 37.5 ± 5.3, IPC 37.5 ± 5.5 mL·kg-1·min-1, P = .6).
IPC before cycling exercise provides an ergogenic benefit that is not attributable to a placebo effect from positive expectation and that was not explained by traditionally suggested mechanisms.
Kyle M.A. Thompson, Alanna K. Whinton, Shane Ferth, Lawrence L. Spriet and Jamie F. Burr
Ischemic preconditioning (IPC) was initially developed to protect the myocardium from ischemia through altered cardiocyte metabolism. Because of the observed effects on metabolism and oxygen kinetics, IPC gained interest as a potential ergogenic aid in sports. Limited research evaluating the effects of IPC on maximal short-duration activities has been performed, and of the existing literature, mixed outcomes resulting from intrasubject variation may have clouded the efficacy of this technique for enhancing sprint performance. Therefore, the current study employed a randomized repeated-measures crossover design with IPC, placebo (SHAM), and control conditions while using sprint-trained athletes (N = 18) to determine the effect of IPC (3 × 5-min occlusions, with 5-min reperfusion), concluding 15 min prior to maximal 10-s and 20-m sprinting. A visual analog scale was used in conjunction with the sprint trials to evaluate any possible placebo effect on performance. Despite a “significantly beneficial” perception of the IPC treatment compared with the SHAM trials (P < .001), no changes in sprint performance were observed after either the IPC or SHAM condition over 10 m (IPC Δ < 0.01 [0.02] s, SHAM Δ < 0.01 [0.02] s) or 20 m (IPC Δ = −0.01 [0.03] s, SHAM Δ < 0.01 [0.03] s) compared with control. Thus, an IPC protocol does not improve 10- or 20-m sprint performance in sprint-trained athletes.
Jennifer Sygo, Alexandra M. Coates, Erik Sesbreno, Margo L. Mountjoy and Jamie F. Burr
Low energy availability (LEA), and subsequent relative energy deficiency in sport, has been observed in endurance, aesthetic, and team sport athletes, with limited data on prevalence in athletes in short-burst activities such as sprinting. We examined prevalence of signs and symptoms of LEA in elite female sprinters at the start of the training season (PRE), and at the end of a 5-month indoor training period (POST). Four of 13 female sprinters (31%) presented at PRE testing with at least one primary (amenorrhea, low bone mineral density, low follicle-stimulating hormone, luteinizing hormone, or estradiol, resting metabolic rate ≤29 kcal/kg fat-free mass, Low Energy Availability in Females Questionnaire score ≥8) and one secondary indicator of LEA (fasting blood glucose <4 mmol/L, free triiodothyronine <3.5 pmol/L, ferritin <25 μg/L, low-density lipoprotein cholesterol >3.0 mmol/L, fasting insulin <20 pmol/L, low insulin-like growth factor-1, systolic blood pressure <90 mmHg, and/or diastolic blood pressure <60 mmHg). At POST, seven out of 13 athletes (54%) presented with at least one primary and one secondary indicator of LEA, three of whom had also presented with indicators of LEA at PRE. Five out of 13 (39%) athletes had previous stress fracture history, though this was not associated with current indicators of LEA (PRE: r = .52, p = .07; POST: r = −.07, p = .82). In conclusion, elite female sprinters may present with signs and symptoms of LEA, even after off-season rest. Medical and coaching staff should be aware of the signs and symptoms of LEA and relative energy deficiency in sport and should include appropriate screening and intervention strategies when working with sprinters.
Brittany T. MacEwen, Travis J. Saunders, Dany J. MacDonald and Jamie F. Burr
Sit-stand desks reduce workplace sitting time among healthy office workers; however, their metabolic and behavioral impact in higher risk populations remains unknown.
25 office workers with abdominal obesity were randomized to an intervention (sit-stand workstation) or control group (seated desk) for 12 weeks. Physical activity, sedentary behavior, and cardiometabolic risk factors were assessed before and after the intervention period in both groups.
In comparison with the control group, which did not change, the intervention group experienced significant reductions in workday (344 ± 107 to 186 ± 101 min/day) and total (645 ± 140 to 528 ± 91 min/day) sitting time, as well as increases in workday standing time (154 ± 108 to 301 ± 101 min/day, P < .05). There were no changes in sitting or standing time outside of work hours, steps taken each day, or any marker of cardiometabolic risk in either group (all P > .05).
Sit-stand desks were effective in reducing workplace sedentary behavior in an at-risk population, with no change in sedentary behavior or physical activity outside of work hours. However, these changes were not sufficient to improve markers of cardiometabolic risk in this population.