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Physiological and biomechanical factors of cycling performance
Full text linkThe two primary predictors of cycling performance are maximal oxygen consumption and lactate threshold. However, several physiological and biomechanical factors influence these variables. The purpose of study one was to investigate relative joint contribution, muscle activation, and muscle oxygenation differences between high (HLT) and low (LLT) lactate threshold cyclists with similar maximal oxygen consumption capabilities (VO [subscript 2max]). While there were no differences in muscle oxygenation, the HLT group had greater relative hip contribution at 90% of VO [subscript 2max] compared to the LLT group, as well as decreased vastus medialis EMG activation during exercise at 60 and 70% of VO [ subscript 2max] (p<0.05). These findings suggesting the HLT cyclists place a greater emphasis on the hip compared to the knee joint to generate power while cycling. The purpose of study two was to investigate the effects of short-term maximal power training on cycling peak oxygen consumption (VO [subscript 2peak-cycling]) in non-cyclists. Over the course of 5 days, the training group performed 10 maximal sprints a day each lasting ~4 seconds with two-minutes rest between each sprint. This protocol was designed to maximize recruitment of muscles involved in cycling while minimizing cardiovascular stress during training. Following training, absolute and relative VO [subscript 2peak-cycling] was 5.9 ± 1.6% and 5.6 ± 1.9% greater compared to pre-training (p<0.05), while in the control group VO [subscript 2peak-cycling] did not change (p>0.05). The improvement in VO [subscript 2peak-cycling] was accompanied by a 6.3 ± 2.5% increase (Pre: 228 ± 18 W vs. Post: 242 ± 19 W) in peak work rate achieved during post-testing in the training group (p<0.05). This suggests that VO [subscript 2peak-cycling] can be increased through maximal power training in non-cyclists likely as a result of increased ability to recruit additional muscle mass during intense cycling exercise. Taken together, these studies indicate that biomechanical muscle recruitment 'strategies' can influence both submaximal (i.e. LT [subscript VO2]) and peak oxygen consumption (i.e. VO [subscript 2peak-cycling]) during cycling.Kinesiology and Health Educatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Oxygen consumption during repeated inertial load exercise sprints with differing recovery durations in older adults
Full text linkAs the generation termed the “baby boomers” continue to age the proportion of older adults in the population continues to climb increasing the demand for viable ways to improve “health span” by exercise to improve cardiovascular and musculoskeletal health and reduce medical costs due to unhealthy aging. Inertial load cycle ergometer (ILE) sprints lasting 4s each, have been shown to provide consistent maximum power outputs in individuals of all ages. This study examined the effect of 60s, 45s, and 30s recoveries between sprints, performed for a total of 15 minutes, on oxygen consumption and heart rate. Six subjects aged 61 ± 2.6 yrs and VO₂ [subscript peaks] of 2.91 ± 0.51 L/min completed three separate trials of 15 ILE sprints with 60s recovery, 20 ILE sprints with 45s recovery, and 30 ILE sprints with 30s recovery during weeks 1, 4, and 8 respectively of a progressive eight-week repeated ILE training program that consisted of three training sessions per week. During each trial 6 of the ILE sprints included VO₂ collection using breath by breath, average of total power, HR, and RPE were recorded across similar time points during each trial. Percentage of VO₂ [subscript peak] was measured at 38.22 ± 2.17, 61.3 ± 6.50, and 59.14 ± 5.31during the trials of 60s, 45s, and 30s recoveries between sprints respectively (60s recovery vs. 45s recovery p=0.0138; 60s recovery vs. 30s recovery p=0.0251). %HR maximal was not statistically different between trials (p=0.133). Within the population there was a correlation between average power maximums and VO₂ (r=.73; p=0.0006), VO₂ and estimated stroke volume (SVEst.) (r=0.94; p <0.0001), and rating of perceived exertion (RPE) and %HR maximal (r=0.24; p<0.05) during each ILE sprint trial. In conclusion, ILE sprints may elicit the same maximal power outputs with 60s, 45s, and 30s recoveries with comparable cardiovascular stress following 45s and 30s recovery periods.Kinesiology and Health Educatio
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Effects of 4-s sprint interval training using an inertial load ergometer on peak oxygen consumption and blood volume
Full text linkBackground: High-intensity interval training (HIIT) is an effective tool to improve cardiovascular fitness and maximal anaerobic power. Different methods of HIIT have been studied, but the effect of a very short exercise time (i.e. 4s) with a high number of repetitions (i.e. 30 bouts) is unknown. Purpose: We examined the effect of inertial-load sprint training (ILST) during cycling over eight weeks on peak oxygen consumption (VO₂ [subscript peak]), blood volume and maximal anaerobic power in 11 young (age: 21.3 ± 0.5 y) recreationally active individuals (6 men, 5 women). Methods: Subjects trained three times a week for eight weeks following the ILST program consisting of 30 bouts of 4s all-out cycling on an inertial-load ergometer with progressively decreasing recovery time (30 to 24 to 15s). Results: ILST elicited significant increases after training in VO₂ [subscript peak] (Pre: 2.86 ± 0.18 L/min, Post: 3.24 ± 0.21 L/min, (p=0.003), maximal anaerobic power and total blood volume (Pre: 5,139 ± 199 ml, Post: 5,529 ± 342 ml, p<0.05). Conclusion: A program employing 30 bouts of 4s inertial load sprint training with progressively reduced recovery time (30 to 15 s) between sprints is effective for improving blood volume, VO₂ [subscript peak] and maximal power in young individuals.Kinesiology and Health Educatio
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Interrupting prolonged sedentary behavior with periodic interval exercise : effects on postprandial lipemia and fat oxidation
Full text linkHigh levels of postprandial lipemia are considered an independent risk factor for cardiovascular disease, one of the leading causes of death worldwide. An acute bout of exercise has been shown to attenuate the plasma triglycerides response the next morning following a meal high in fat. However, evidence suggests that this benefit of exercise is not always observed when time spent sitting is drastically increased. This phenomenon is being described as exercise resistance, where the metabolic benefits of exercise do not manifest. A previous study found that breaking up prolonged sitting with inertial load ergometer (ILE) (5 x 4second sprints with 45 seconds rest) sprints every hour for 8 hours attenuated postprandial lipemia in healthy adults. The purpose of this study is to determine if these benefits can still be gained with less frequent intervals of breaking up induced sedentary behavior (monitored by restricting step count to <4500 steps/day) using the same exercise protocol. In a repeated measure, crossover design, eight healthy, young adults (four men and four women) participated in three trials which lasted a total of four days each: two controlled activity days, one intervention day, and a high fat tolerance test (HFTT) on day 4. The controlled activity days required participants to take less than 4500 steps each day to induce exercise resistance. The interventions consisted of taking less than 4500 steps/d with no exercise (SIT), with 4 bouts of ILE sprints (SIT + 4), and with 2 bouts of ILE sprints (SIT + 2) spread throughout the day. The outcome measure was postprandial metabolism following a high fat meal. During the HFTT, plasma triglycerides and expired air were collected hourly for four hours after meal ingestion. Incremental and total area under the curve (AUC) for plasma triglycerides concentration were calculated and indirect calorimetry was performed to quantify fat oxidation. No differences (P>0.05) were found between interventions for plasma triglycerides total and incremental AUC or fat oxidation. These results suggest 2 or 4 bouts of ILE sprint exercise breaking up 8-hours of sitting are not enough to ameliorate the postprandial responses to a high fat meal the next day.Kinesiology and Health Educatio
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The effects of dietary carbohydrate and fat and fatty acid availability on muscle glycogen and triglyceride and substrate utilization during and after exercise
No full texttextThese studies determined the effects of altering dietary fat and carbohydrate on
intramuscular substrate concentrations and subsequent substrate utilization during
moderate intensity exercise, as well as on plasma triglyceride (TG) concentration. A
two-day high fat / low-carbohydrate diet (HF/LC; 60% fat, 25% carbohydrate)
elevated intramuscular TG (IMTG) concentration by 36% (36.8±4.8 vs. 49.9±3.4
mmol/kg dry weight, p<0.05) and decreased muscle glycogen concentration to 49%
(348±36 vs. 716±68 mmol/kg dry weight, p<0.05) of normal (i.e.; with a diet of 25%
fat; 65% carbohydrate). HF/LC produced a 71% increase in fat oxidation (32.4±2.2
vs. 18.8±2.4 µmol/kg/min), a 79% increase in whole body lipolysis, and a 38%
decrease in muscle glycogen oxidation (all p<0.05). Elevated plasma FFA
concentration was not essential for this diet-induced increase in fat oxidation because
the adipose lipolysis inhibitor, Acipimox®, did not effect the marked increase in fat
oxidation despite the severe suppression of plasma FFA throughout exercise. Furthermore, the increase in fat oxidation was associated with a tendency for
significant IMTG breakdown during exercise (8.8±3.3 mmol/kg dw/60min, p=0.06)
which fully compensated for the decrease in muscle glycogen oxidation as plasma
glucose uptake (Rd glucose) was unaffected by the HF/LC diet. However, the diet induced increase in fat oxidation, presumably IMTG oxidation, was attenuated by
non-selective β-adrenergic blockade (80 mg propanolol), as low muscle glycogen
oxidation was also compensated by a 15% increase in Rd glucose (p<0.05).
Interestingly, the addition of ~100 g fat / d to a diet containing only 2% fat (7 g/d) did
not effect IMTG concentration or fat oxidation. Furthermore, HF/LC also resulted in
a general lowering of plasma TG concentration at rest in the fasted and postprandial
states, and during exercise (all p<0.05). In summary, low muscle glycogen
concentration associated with a HF/LC diet is primarily compensated by elevated
IMTG concentration and oxidation during exercise whereas increases in plasma
glucose uptake occur only when the increase in fat oxidation is limited (e.g.; βblockade). It seems that a high fat diet increases IMTG concentration and oxidation
which prevents excessive Rd glucose and hypoglycemia yet this requires a decrease
in dietary carbohydrate and/or muscle glycogen concentration.Kinesiology and Health Educatio
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The effects of prolonged standing compared to prolonged sitting on postprandial lipemia
Full text linkProlonged periods of sedentary behavior are linked to cardiometabolic disease independent of many risk factors including exercise and activity levels. This study examined the effects of posture, rather than activity by comparing one full day of sitting (14.45 ± 0.286 hours) compared to one full day of standing (12.22 ± 0.105 hours) on postprandial metabolism and lipemia. Eighteen subjects aged 23.72 ± 0.795 years completed two (sit/stand), four-day trials in a randomized crossover design. The first two days of the trial were control days where activity and diet were matched across trials. The third day involved one full day of sitting or standing. The fourth day was a high fat tolerance test, in which blood and gas samples were collected immediately before and for six hours after the ingestion of a high fat shake (1.34, 0.92, 0.17 g/kg body weight of fat, carbohydrate, and protein, respectively). Indirect calorimetry was used to measure metabolic rate and substrate oxidation while spectrophotometry was used to measure plasma concentration. Area under the curve (AUC) for the postprandial responses in plasma glucose and triglyceride were calculated with the trapezoidal rule. Prolonged standing resulted in significantly lower plasma triglyceride concentration (p=0.036) and an 11.3% decrease in total AUC (p=0.022) compared to sitting, but no change in incremental AUC (AUCi) was detected (p=0.186). There were no changes in substrate oxidation (p=0.522) or plasma glucose glucose concentration (p=0.776) during the high fat tolerance test. The study shows that posture does influence the lipid profile independent of exercise or activity by increasing the clearance of triglyceride from the blood stream without increasing the oxidation of fatKinesiology and Health Educatio
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Maximal power measured during a taper in collegiate swimmers
No full textThis study determined the time course of changes in maximal neuromuscular power (W), torque (nM), velocity (rpm), and swim performance (m·s⁻¹) that occurred in collegiate swimmers during the taper portion of their season. Using an arm ergometer with inertial loading, measurements were made during the week prior to in the initiation of the taper (high-volume, HV), during the two to three week period of the taper (Taper), and during the week of peak competition (Peak) in 46 competitive collegiate swimmers (22 female, 24 male). Subjects were divided into groups that tapered to peak for competition at either the conference or national championship meet. Groups include: Men’s Conference team (MC, n = 13), Men’s National team (MN, n = 11), Women’s Conference team (WC, n = 22), and Women’s National team (WN, n =15). MC increased power 10.2 % (p < 0.01) and swim performance 4.4% (p < 0.001). MN increased power 11.6% (p < 0.01), torque 7.4% (p < 0.02) and swim performance 4.7% (p< 0.001). WC increased power 10.4% (p < 0.001), velocity 4.1% (p < 0.05), torque 6.5% (p < 0.01) and swim performance 5.2% (p < 0.001). WN increased power 13.5% (p < 0.001), velocity 6.1% (p < 0.04), torque 8.7% (p < 0.04), and swim performance 5.5% (p < 0.001). Overall, approximately one-half of the increase in maximal neuromuscular power occurred during the first 7 to 10 days of taper with the remaining increase occurring during the last two weeks of taper. Torque displayed a similar time course for improvement when compared to power, as the majority of the increase occurred during the first 7 to 10 days of taper, with the only exception being MC. Velocity was only significantly increased in the women and the time frame with which this increase occurred lacked consistency across groups. Performance was significantly correlated to both power and torque in all groups (p < 0.05). In summary, maximal neuromuscular power increases during a taper of collegiate swimmers largely due to the increases in torque with one half of the increase in power occurring in the first 7 to 10 days of the three week taperKinesiology and Health Educatio
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The efficacy of Nexersys training for improving body composition and cardiovascular fitness
Full text linktextPurpose: This is the first study done to determine the efficacy of 10-weeks of Nexersys training on improving cardiovascular fitness (CF) and body composition (BC). Nexersys is an "exergaming" system that combines mixed martial arts, high-intensity interval training and core work into an interactive unit with a monitor and 7-strike pads. Participants were provided a Nexersys unit in their homes to complete 10-weeks of training 3 to 4 times a week progressing from 5, 3-min rounds with a minute rest to 15 rounds at the end of 10-weeks. Participants were tested on 3 separate occasions, prior to beginning training (0wk), at 5-weeks (5wk) and 10-weeks (10wk). Body mass (BM), percent body fat (%BF), fat mass (FM) and lean mass (LM) were assessed using dual-energy X-ray absorptiometry (DEXA). CF was assessed during a 10-round Nexersys bout (NB) and a VO2max treadmill (VO2max) test. CF during NB and VO2max treadmill test was assessed by using regression analysis to determine the estimated average heart rate for a range of VO2 10-25 ml/kg/min (HRN) and 10-30 ml/kg/min (HRV) respectively. Results and Conclusion: Relative to starting values, BM did not change (79.8 ± 7.9 to 79.7 ± 7.5 kg). %BF and FM decreased from starting values (36.0 ± 3.4% to 34.1 ± 5.3%, p=0.003 and 30.0 ± 4.9 kg to 28.4 ± 4.6 kg, p=0.045, respectively). LM increased from starting values (46.7 ± 3.5kg to 48.4 ± 3.6kg, p=0.001). HRN and HRV decreased from starting (148 ± 2.7 to 140.8 ± 1.9 bpm, p=0.003 and 148 ± 1.8 to 140.1 ± 1.8 bpm, p=0.003, respectively). VO2max trended to increase but did not reach statistical significance (33.9 ± 1.7 to 36.3 ± 1.7 ml/kg/min, p=0.054). These findings suggest 10-weeks of Nexersys training improves body composition both by increasing LM and decreasing BF with no change in BM. CF improved at submaximal intensities.Kinesiology and Health Educatio
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