Tuesday, March 31, 2015

Exercise Research Update March 2015: Citrate as pH Buffer not Effective, Circuit Beats HIIT Training for CV Health and Strength & More, Mental Fatigue & Anaerobic Performance

Welcome to today's SV Exercise Research Update ;-)
Time for a brief overview of the latest papers from the European Journal of Applied Physiology. Well, at least the ones that are of potential interest to gymrats, personal trainers and people working in the health and fitness industry.

I have to admit. The studies are no longer "ahead of print" and thus actually from 2014, but that does not mean that they cannot be interesting news to you and would no longer be worth discussing, right?
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  • Impact of acute sodium citrate ingestion on endurance running performance in a warm environment (Vaher. 2014)

    Figure 1: Compared to bicarbonate, the pH buffering effects of sodium citrate are mediocre at best (Vaher. 2014).
    Main results: Acute CIT ingestion induces alkalosis, water retention, plasma volume expansion and an increase in post-exercise blood lactate concentration, but does not improve 5,000-m running performance in a warm environment in non-heat-acclimated endurance-trained males.

    What do you have to know about the methods? Not much, the scientists had 116 non-heat-acclimated endurance-trained males (age 25.8 ± 4.4 years, VO2peak 56.9 ± 4.7 mL kg min) complete two 5,000-m self-paced treadmill runs with preceding CIT or placebo (wheat flour; PLC) ingestion in a double-blind, randomized, crossover manner in a climatic chamber (air temperature 32 °C, relative humidity 50 %). The active treatment consisted of 500 mg/kg body mass sodium citrate that were consumed as a bolus within 30 minutes before the testing sessions.

    What do we make of the results? Easy, sodium bicarbonate will always outperform citrate due to having immediate vs. kidney modulated pH buffering effects. Stay away from citrates, if you want performance benefits read my previous articles about sodium bicarbonate and use that instead.
  • Short- and long-term reliability of heart rate variability indices during repetitive low-force work (Hallman. 2014)

    Main results: HRV can be used as a reliable and feasible marker of autonomic activity in occupational studies of repetitive low-force work.

    What do you have to know about the methods? Fourteen healthy female subjects performed a standardized pipetting task in the laboratory on three separate days within a short-time span (<2 weeks), and on one additional occasion 6 months later. A number of standard HRV indices were calculated in both time and frequency domains. For each HRV index, variance components were estimated between subjects, within subjects between occasions far apart in time, and within subjects between days within a 2-week period.

    What do we make of the results? In contrast to previous studies the study at hand etermined the variability between and within subjects of common HRV indices during a repetitive low-force occupational task, i.e., pipetting, and interpreted the results in terms of necessary sample sizes in studies comparing HRV between conditions or groups. That's different to the usual exercise tests and that it still worked broadens the applicability of HRV measures.
  • An Ironman triathlon reduces neuromuscular performance due to impaired force transmission and reduced leg stiffness (Mueller. 2014)

    Main results: The scientists observed a significantly reduced counter-movement jump hight of which they were able to show that it was a result of the lower positive impulse. Thus, it should be obvious that Ironman races induce a neuromuscular deficit due to impairments in force transmission, resulting in a lower average positive force during CMJ, because of a slower rate of force development.

    What do you have to know about the methods? It is pretty obvious that the study involved measuring countermovement jump (CMJ), squat jump (SJ), and multiple one-legged hopping (m1LH) to assess fatigue-related alterations in mechanical variables in thirteen male non-professional triathletes in response to an Ironman race.

  • What do we make of the results? Not really much. I mean you didn't really expect to be at the peak of your physical performance right after an ironman race, right? So, if anything, the study results highlight the importance of neuromuscular vs. mere muscular fatique after endurance events.
  • Peripheral heart action (PHA) training as a valid substitute to high intensity interval training to improve resting cardiovascular changes and autonomic adaptation (Piras. 2014)

    Main results: After 30 training sessions performed in 3 months, PHA resistance exercise promoted cardiovascular adaptations, with a decrease in the power spectral component of vascular sympathetic activity and an increase in the vagal modulation. Low-frequency oscillation estimated from systolic blood pressure variability seems to be a suitable index of the sympathetic modulation of vasomotor activity.

    Figure 2: Piras et al. observed both decreases in blood pressure and strength gains that were more pronounced in the PHA vs. HIIT group (Piras. 2014).
    What is peripheral heart action training? Each PHA session started with a 5-min warm-up and concluded with a cool-down. The conditioning phase of each session involved circuit weight training and consisted of six resistance exercise stations, as strictly ordered: pectoral machine, leg extension, lat machine, leg curl, shoulder press and calf machine. Subjects performed 15 repetitions of pectoral machine, and then moved to the next station (leg extension) with active pauses (e.g., subjects performed an exercise of the lower limbs as soon as they have finished one on the upper limbs, and vice versa), until the com pletion of the circuit training (calf machine).

    Such circuit training was performed four times, separated by 1-min of rest. Resistance was increased for the next exercise session if the subject could perform fifteen complete repetitions during the final set for each exercise. Subjects wore a heart rate monitor and maintained an intensity around 55–60 % of 1-RM, which corresponded approximately to 60–80 % of maximal heart rate calculated during the pre-test.

    What to make of the results? Next to the beneficial effects on cardiovascular fitness, the increased muscular strength in response to this particular form of resistance training has been linked to reduced all-cause mortality and the prevalence of metabolic syndrome, independent of cardiorespiratory fitness levels. So, basically you can kill two birds with a stone if you have clients perform peripheral heart action training.
Figure 3: Mean power output profile (a) and time course of cadence (b) for mental fatigue and control condition (Martin. 2014).
Last but not least, Martin et al. found that "mental fatigue does not affect maximal anaerobic exercise performance." An observation that appears odd considering the fact that my workouts such, whenever I feel mentally fatigued. In their study, however, the scientists from the University of Canberra found "[v]ear identical responses in performance and physiological parameters between mental fatigue and control conditions" which clearly indicates that peripheral mechanisms primarily regulate maximal anaerobic exercise.

Or, practically speaking: "Whereas mental fatigue can negatively impact submaximal endurance exercise, it appears that explosive power, voluntary maximal strength and anaerobic work capacity are unaffected" (Martin. 2014).

Well, when I come to think about it, the kind of mental fatigue that was induced by computer-based tasks before the workout in the study at hand does not thwart me either | Comment on Facebook!
References:
  • Hallman, David M., Divya Srinivasan, and Svend Erik Mathiassen. "Short-and long-term reliability of heart rate variability indices during repetitive low-force work." European journal of applied physiology (2014): 1-10.
  • Martin, Kristy, et al. "Mental fatigue does not affect maximal anaerobic exercise performance." European journal of applied physiology (2014): 1-11.
  • Mueller, Sandro Manuel, et al. "An Ironman triathlon reduces neuromuscular performance due to impaired force transmission and reduced leg stiffness." European journal of applied physiology (2014): 1-8.
  • Piras, Alessandro, et al. "Peripheral heart action (PHA) training as a valid substitute to high intensity interval training to improve resting cardiovascular changes and autonomic adaptation." European journal of applied physiology (2014): 1-11.
  • Vaher, Ivi, et al. "Impact of acute sodium citrate ingestion on endurance running performance in a warm environment." European journal of applied physiology (2014): 1-11.