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Beta-alanine improves sprint performance in endurance cycling

26 Oct

Recent research has shown that chronic dietary beta-alanine (betaALA) supplementation increases muscle carnosine content, which is associated with better performance in short (1-2 min) maximal exercise. Success in endurance competitions often depends on a final sprint. However, whether betaALA can be ergogenic in sprint performance at the end of an endurance competition is at present unknown. Therefore, a study published in 2009 entitled ‘Beta-alanine improves sprint performance in endurance cycling’ investigated the effect of 8-wk betaALA administration in moderately to well-trained cyclists on sprint performance at the end of a simulated endurance cycling race.

METHODS: A double-blind study was performed, which consisted of two experimental test sessions interspersed by an 8-wk betaALA (2-4 g.d; n = 9) or matched placebo (PL; n = 8) supplementation period. In the pretesting and the posttesting, subjects performed a 10-min time trial and a 30-s isokinetic sprint (100 rpm) after a 110-min simulated cycling race. Capillary blood samples were collected for determination of blood lactate concentration and pH.

RESULTS: Mean power output during the time trial was approximately 300 W and was similar between PL and betaALA during either the pretesting or the posttesting. However, compared with PL, during the final sprint after the time trial, betaALA on average increased peak power output by 11.4% (95% confidence interval = +7.8 to +14.9%, P = 0.0001), whereas mean power output increased by 5.0% (95% confidence interval = +2.0 to +8.1%, P = 0.005). Blood lactate and pH values were similar between groups at any time.

CONCLUSION: Oral betaALA supplementation can significantly enhance sprint performance at the end of an exhaustive endurance exercise bout.

Effect of Ambient Temperature on Gross Efficiency

25 Oct

 

Time-trial performance deteriorates in the heat. This might potentially be the result of a temperature-induced decrease in gross-efficiency (GE). The effect of high ambient temperature on GE during cycling was examined in a study published last 2007 in the European Journal of Applied Physiology entitled ‘Effect of Ambient Temperature on Gross Efficiency in Cycling’, with the intent of determining if a heat-induced change in GE could account for the performance decrements in time trial exercise found in literature. Ten well-trained male cyclists performed 20-min cycle ergometer exercise at 60% PVO2max (power output at which VO2max was attained) in a thermo-neutral climate (N) of 15.6+/-0.3 degrees C, 20.0+/-10.3% RH and a hot climate (H) of 35.5+/-0.5 degrees C, 15.5+/-3.2% RH. GE was calculated based on VO2 and RER. Skin temperature (Tsk), rectal temperature (Tre) and muscle temperature (Tm) (only in H) were measured.

GE was 0.9% lower in H compared to N (19.6+/-1.1% vs. 20.5+/-1.4%) (P<0.05). Tsk (33.4+/-0.6 degrees C vs. 27.7+/-0.7 degrees C) and Tre (37.4+/-0.6 degrees C vs. 37.0+/-0.6 degrees C) were significantly higher in H. Tm was 38.7+/-1.1 degrees C in H. GE was lower in heat. Tm was not high enough to make mitochondrial leakage a likely explanation for the observed reduced GE. Neither was the increased Tre. Increased skin blood flow might have had a stealing effect on muscular blood flow, and thus impacted GE. Cycling model simulations showed, that the decrease in GE could account for half of the performance decrement. GE decreased in heat to a degree that could explain at least part of the well-established performance decrements in the heat.

Carbohydrate-Protein and cycling performance

28 Sep

We’ve featured several studies on sports drinks and beverages, and it’s common knowledge that a lot of studies offer conflicting results. Such is the world of sports medicine. Depending on the design of the study, the recommendations of some studies would differ greatly from other supposedly similar studies. In the topic of sports beverages, there is still no consensus among experts as to the ideal choice to improve cycling performance. What we have instead are conflicting studies.

Just this June of 2010, a study published in the Medicine and Science in sports and exercise journal aimed to determine whether adding protein to a CHO beverage would improve late-exercise cycle time-trial performance over CHO alone. Furthermore, the study examined the effects of coingesting protein with CHO during exercise on postexercise markers of sarcolemmal disruption and the recovery of muscle function.

In a double-blind, crossover design, 12 trained male cyclists performed 120 min of steady-state (SS) cycling at approximately 55% VO2max followed by a time trial lasting approximately 1 h. At 15-min intervals during SS exercise, participants consumed either a CHO or a CHO + protein (CHO + Pro) beverage (providing 65 g x h(-1) CHO or 65 g x h(-1) CHO plus 19 g x h(-1) protein). Twenty-four hours after the onset of the SS cycle, participants completed a maximum isometric strength test. At rest and 24 h postexercise, a visual analog scale was used to determine lower-limb muscle soreness, and blood samples were obtained for plasma creatine kinase concentration. Dietary control was implemented 24 h before and during the time course of each trial.

Average power output sustained during time trial was similar for CHO and CHO + Pro, with no effect of treatment on the time to complete the time trial (60:13 +/- 1:33 and 60:51 +/- 2:40 (min:s) for CHO and CHO + Pro, respectively). Postexercise isometric strength significantly declined for CHO (15% +/- 3%) and CHO + Pro (11% +/- 3%) compared with baseline (486 +/- 28 N). Plasma creatine kinase concentrations, and visual analog scale soreness significantly increased at 24 h postexercise, with no difference between treatments.

The present findings suggest that CHO + Pro coingestion during exercise does not improve late-exercise time-trial performance, ameliorate markers of sarcolemmal disruption, or enhance the recovery of muscle function at 24 h postexercise over CHO alone.

Cycling Mechanics and Core Stability

24 Sep

In recent years, fitness practitioners have increasingly recommended core stability exercises in sports conditioning programs. Greater core stability may benefit sports performance by providing a foundation for greater force production in the upper and lower extremities. Traditional resistance exercises have been modified to emphasize core stability. Such modifications have included performing exercises on unstable rather than stable surfaces, performing exercises while standing rather than seated, performing exercises with free weights rather than machines, and performing exercises unilaterally rather than bilaterally.

Despite the popularity of core stability training, relatively little scientific research has been conducted to demonstrate the benefits for healthy athletes. Based on the current literature, prescription of core stability exercises should vary based on the phase of training and the health status of the athlete. During preseason and in-season mesocycles, free weight exercises performed while standing on a stable surface are recommended for increases in core strength and power. Free weight exercises performed in this manner are specific to the core stability requirements of sports-related skills due to moderate levels of instability and high levels of force production. Conversely, during postseason and off-season mesocycles, Swiss ball exercises involving isometric muscle actions, small loads, and long tension times are recommended for increases in core endurance.

Furthermore, balance board and stability disc exercises, performed in conjunction with plyometric exercises, are recommended to improve proprioceptive and reactive capabilities, which may reduce the likelihood of lower extremity injuries.

A recent study in the National Journal of Strength and Conditioning Research outlined the importance of core training for cyclists. The title of this study was “Relationship Between Cycling Mechanics and Core Stability”. The purpose of the study was to determine whether cycling mechanics are affected by core stability. The foundation behind core training for cyclists is that pelvic stabilization maintains a natural curvature of the spine. The core is defined as the collection of primary stabilizing muscles for both the front and the back of the pelvis and lower back. A weak core could potentially inhibit power production, since the pelvis is the “lever” for the psoas and gluteal muscles, both of which are your cycling power muscles. If your lower extremities are not aligned properly and the lever is in an incorrect position, then power is compromised.

Hip, knee, and ankle joint kinematic and pedal force data were collected on 15 competitive cyclists while cycling untethered on a high-speed treadmill. The exhaustive cycling protocol consisted of cycling at 25.8 km x h(-1) while the grade was increased 1% every 3 minutes.

A core fatigue workout was performed before the second treadmill test. Total frontal plane knee motion (test 1: 15.1 +/- 6.0 degrees ; test 2: 23.3 +/- 12.5 degrees), sagittal plane knee motion (test 1: 69.9 +/- 4.9 degrees ; test 2: 79.3 +/- 10.1 degrees), and sagittal plane ankle motion (test 1: 29.0 +/- 8.5 degrees ; test 2: 43.0 +/- 22.9 degrees) increased after the core fatigue protocol.

No significant differences were demonstrated for pedaling forces. Core fatigue resulted in altered cycling mechanics that might increase the risk of injury because the knee joint is potentially exposed to greater stress. Improved core stability and endurance could promote greater alignment of the lower extremity when riding for extended durations as the core is more resistant to fatigue.

During a cycling event, the pelvis is fixed in a constant position, and subjected to tens of thousands of muscle contraction repetitions. If the core breaks down during this time due to fatigue, then the pelvis will shift and wattage will suffer. So even if the legs are ideally prepared and adequately tapered, a cyclist could still have subpar results. Core training then has become an essential part of the cycling training regimen.

Once a day versus Twice every second day Endurance Training

21 Sep

A study entitled ‘Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens.’ was published last 2008 with the aim of determining the effects of a cycle training program in which selected sessions were performed with low muscle glycogen content on training capacity and subsequent endurance performance, whole body substrate oxidation during submaximal exercise, and several mitochondrial enzymes and signaling proteins with putative roles in promoting training adaptation.

Seven endurance-trained cyclists/triathletes trained daily (High) alternating between 100-min steady-state aerobic rides (AT) one day, followed by a high-intensity interval training session (HIT; 8 x 5 min at maximum self-selected effort) the next day. Another seven subjects trained twice every second day (Low), first undertaking AT, then 1-2 h later, the HIT. These training schedules were maintained for 3 wk. Forty-eight hours before and after the first and last training sessions, all subjects completed a 60-min steady-state ride (60SS) followed by a 60-min performance trial.

Muscle biopsies were taken before and after 60SS, and rates of substrate oxidation were determined throughout this ride. Resting muscle glycogen concentration (412 +/- 51 vs. 577 +/- 34 micromol/g dry wt), rates of whole body fat oxidation during 60SS (1,261 +/- 247 vs. 1,698 +/- 174 micromol.kg(-1).60 min(-1)), the maximal activities of citrate synthase (45 +/- 2 vs. 54 +/- 1 mmol.kg dry wt(-1).min(-1)), and beta-hydroxyacyl-CoA-dehydrogenase (18 +/- 2 vs. 23 +/- 2 mmol.kg dry wt(-1).min(-1)) along with the total protein content of cytochrome c oxidase subunit IV were increased only in Low (all P < 0.05).

Mitochondrial DNA content and peroxisome proliferator-activated receptor-gamma coactivator-1alpha protein levels were unchanged in both groups after training. Cycling performance improved by approximately 10% in both Low and High.

The study concluded that compared with training daily, training twice every second day compromised high-intensity training capacity. While selected markers of training adaptation were enhanced with twice a day training, the performance of a 1-h time trial undertaken after a 60-min steady-state ride was similar after once daily or twice every second day training programs.

Fish oil, Exercise and Performance

21 Sep

Dietary omega-3 polyunsaturated fatty acids (PUFAs) are readily incorporated into heart and skeletal muscle membranes where, in the heart, animal studies show they reduce O2 consumption.

To test the hypothesis that omega-3 PUFAs alter O2 efficiency in humans, the effects of fish oil (FO) supplementation on O2 consumption during exercise were evaluated. Sixteen well-trained men (cyclists), randomly assigned to receive 8 x 1 g capsules per day of olive oil (control) or FO for 8 weeks in a double-blind, parallel design, completed the study (control: n = 7, age 27.1 +/- 2.7 years; FO: n = 9, age 23.2 +/- 1.2 years). Subjects used an electronically braked cycle ergometer to complete peak O2 consumption tests (VO 2peak) and sustained submaximal exercise tests at 55% of peak workload (from the VO 2peak test) before and after supplementation.

Whole-body O2 consumption and indirect measurements of myocardial O2 consumption [heart rate and rate pressure product (RPP)] were assessed. FO supplementation increased omega-3 PUFA content of erythrocyte cell membranes. There were no differences in VO 2peak (mL kg(-1) min(-1)) (control: pre 66.8 +/- 2.4, post 67.2 +/- 2.3; FO: pre 68.3 +/- 1.4, post 67.2 +/- 1.2) or peak workload after supplementation. The FO supplementation lowered heart rate (including peak heart rate) during incremental workloads to exhaustion (P < 0.05). In addition, the FO supplementation lowered steady-state submaximal exercise heart rate, whole-body O2 consumption, and RPP (P < 0.01). Time to voluntary fatigue was not altered by FO supplementation.

This study indicates that FOs may act within the healthy heart and skeletal muscle to reduce both whole-body and myocardial O2 demand during exercise, without a decrement in performance.

A study on isokinetic cycling versus weight training

20 Sep

A study entitled “Effect of isokinetic cycling versus weight training on maximal power output and endurance performance in cycling” was published last July 2010 with the aim of comparing the effects of a weight training program for the leg extensors with isokinetic cycling training (80 rpm) on maximal power output and endurance performance.

Both strength training interventions were incorporated twice a week in a similar endurance training program of 12 weeks. Eighteen trained male cyclists (VO(2peak) 60 +/- 1 ml kg(-1) min(-1)) were grouped into the weight training (WT n = 9) or the isokinetic training group (IT n = 9) matched for training background and sprint power (P (max)), assessed from five maximal sprints (5 s) on an isokinetic bicycle ergometer at cadences between 40 and 120 rpm.

Crank torque was measured (1 kHz) to determine the torque distribution during pedaling. Endurance performance was evaluated by measuring power, heart rate and lactate during a graded exercise test to exhaustion and a 30-min performance test. All tests were performed on subjects’ individual race bicycle. Knee extension torque was evaluated isometrically at 115 degrees knee angle and dynamically at 200 degrees s(-1) using an isokinetic dynamometer. P (max) at 40 rpm increased in both the groups (~15%; P < 0.05).

At 120 rpm, no improvement of P (max) was found in the IT training group, which was possibly related to an observed change in crank torque at high cadences (P < 0.05). Both groups improved their power output in the 30-min performance test (P < 0.05). Isometric knee extension torque increased only in WT (P < 0.05).

In conclusion, at low cadences, P (max) improved in both training groups. However, in the IT training group, a disturbed pedaling technique compromises an improvement of P (max) at high cadences.

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