Friday, January 23, 2015

Strength Training for Pedaling Performance in Cyclists; HIIT vs. Subcutaneous Fat; Half-Time Re-Warm Up Crucial for Footballers; Using Different Shoes to Prevent Injury & More

If you want to keep up with the latest science from exercise research labs around the world, today's installment of the SuppVersity Short News is for you!
It's time for another exercise research update. This time with the latest study from the latest issue Scandinavian Journal of Medicine & Science in Sports. Studies with topics that range from performance enhancement to injury prevention and are relevant for the average and extraordinary gymrat. In other words, studies for you, me, her and him ;-)

Before we get to the details, I want to thank everyone for the positive feedback on the previous research updates. It's your feedback that allows me to tailor this website to your interests, which is why I am happy about both praise and constructive criticism on Facebook.
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  • Strength training improves performance and pedaling characteristics in elite cyclists (Habets. 2015) - The purpose of the latest study from the Lillehammer University College was to investigate the effect of 25 weeks heavy strength training in young elite cyclists.

    Nine cyclists performed endurance training and heavy strength training (ES) while seven cyclists performed endurance training only (E). ES, but not E, resulted in increases in isometric half squat performance, lean lower body mass, peak power output during Wingate test, peak aerobic power output (Wmax), power output at 4 mmol/L lactate concentrations, mean power output during 40-min all-out trial, and earlier occurrence of peak torque during the pedal stroke (P < 0.05).
    Figure 1: Pre- vs. post changes (%) in relevant performance markers (Habets. 2015)
    As you can see in Figure 1 the ES group achieved superior improvements in Wmax and mean power output during 40-min all-out trial compared with E (P < 0.05). The improvement in 40-min all-out performance was associated with the change toward achieving peak torque earlier in the pedal stroke (r = 0.66, P < 0.01). Neither of the groups displayed alterations in VO2max or cycling economy.

    In conclusion, heavy strength training leads to improved cycling performance in elite cyclists as evidenced by a superior effect size of ES training vs E training on relative improvements in power output at 4 mmol L lactacte levels and peak power output during 30-s Wingate test, Wmax, and mean power output during 40-min all-out trial.
  • Controlled-frequency breath swimming improves swimming performance and running economy (Lavin. 2015) - Respiratory muscle fatigue can negatively impact athletic performance, but swimming has beneficial effects on the respiratory system and may reduce susceptibility to fatigue. Limiting breath frequency during swimming further stresses the respiratory system through hypercapnia and mechanical loading and may lead to appreciable improvements in respiratory muscle strength. The latest study from the Human Performance Laboratory at the Ball State University assessed the effects of controlled-frequency breath (CFB) swimming on pulmonary function.

    Figure 2: Sign. intergroup differences were observed for the total and rel. number of breaths (Lavin. 2015).
    Eighteen subjects (10 men), average (standard deviation) age 25 (+/-6) years, body mass index 24.4 (+/- 3.7) kg/m², underwent baseline testing to assess pulmonary function, running economy, aerobic capacity, and swimming performance. Subjects were then randomized to either CFB or stroke-matched (SM) condition. Subjects completed 12 training sessions, in which CFB subjects took two breaths per length and SM subjects took seven.

    Post-training, maximum expiratory pressure improved by 11% (15) for all 18 subjects (P < 0.05) while maximum inspiratory pressure was unchanged. Running economy improved by 6 (9)% in CFB following training (P < 0.05). Forced vital capacity increased by 4% (4) in SM (P < 0.05) and was unchanged in CFB. As the scientists point out, "[t]hese findings suggest that limiting breath frequency during swimming may improve muscular oxygen utilization during terrestrial exercise in novice swimmers" (Lavin. 2015).
  • Changes in peak fat oxidation in response to different doses of endurance training (Rosenkilde. 2015) - The latest study from the University of Copenhagen probed the effects of different doses of endurance training on the capacity to oxidize fat during exercise in sedentary, overweight men and assessed the association of these variables with changes in peak fat oxidation (PFO).

    Young, sedentary, overweight men were randomized to either the high-dose (HIGH, 600 kcal/day, n = 17) or moderate-dose (MOD, 300 kcal/day, n = 18) endurance training groups or controls (CON, n = 15). PFO and peak oxygen uptake (VO2 peak) were measured using indirect calorimetry, body composition using dual-energy x-ray absorptiometry, and protein levels of mitochondrial enzymes determined by Western blotting.
    Figure 3: Peak fat oxidation during a graded exercise test expressed as (a) absolute amount or (b) relative to fat-free mass at baseline (Pre) and at the end of a 12-week intervention (Post) in sedentary controls (CON, n = 15), a moderate-dose exercise group (MOD, n = 18), and a high-dose exercise group (HIGH, n = 17); while the high intensity exercise was more effective it was not extremely superior  (Rosenkilde. 2015).
    PFO increased in both MOD [1.2 mg/kg fat-free mass (FFM)/min, 95% confidence interval (CI): 0.08:2.3, P = 0.03] and HIGH (1.8 mg/kg FFM/min, CI: 0.6:2.9, P < 0.001) compared with CON. Skeletal muscle expression of citrate synthase, β-hydroxyacyl-CoA dehydrogenase, and mitochondrial oxphos complexes II-V increased similarly in MOD and HIGH. Stepwise multiple linear regression analysis with backward elimination of individual variables correlated with changes in PFO revealed increases in cycling efficiency, FFM, and VO2 peak as the remaining associated variables.

    The scientists conclude that the peak fatty acid oxidation (PFO) during exercise increased with both moderate- and high-dose endurance training. In that, the increases in PFO were mainly predicted by changes in VO2 peak, FFM, and cycling efficiency, and less with skeletal muscle mitochondrial enzymes.
  • Can parallel use of different running shoes decrease running-related injury risk? (Malisoux. 2015) - The aim of the latest study from the Public Research Centre for Healt in Luxembourg was to determine if runners who use concomitantly different pairs of running shoes are at a lower risk of running-related injury (RRI).

    Recreational runners (n = 264) participated in this 22-week prospective follow-up and reported all information about their running session characteristics, other sport participation and injuries on a dedicated Internet platform. A RRI was defined as a physical pain or complaint located at the lower limbs or lower back region, sustained during or as a result of running practice and impeding planned running activity for at least 1 day.
    Figure 4: Relative (%) reduction in hazard ratio for injury risk (Malisoux. 2015)
    One-third of the participants (n = 87) experienced at least one RRI during the observation period. The adjusted Cox regression analysis revealed that the parallel use of more than one pair of running shoes was a protective factor [hazard ratio (HR) = 0.614; 95% confidence interval (CI) = 0.389–0.969], while previous injury was a risk factor (HR = 1.722; 95%CI = 1.114–2.661). Additionally, increased mean session distance (km; HR = 0.795; 95%CI = 0.725–0.872) and increased weekly volume of other sports (h/week; HR = 0.848; 95%CI = 0.732–0.982) were associated with lower RRI risk.

    Multiple shoe use and participation in other sports are strategies potentially leading to a variation of the load applied to the musculoskeletal system. They could be advised to recreational runners to prevent RRI.
  • Half-time re-warm up increases performance capacity in male elite soccer players (Edholm. 2015) - The latest study from the Örebro University investigated the acute effects of a half-time re-warm up on performance and movement patterns in soccer match play. Using a crossover design, 22 professional male players performed traditional passive rest (CON) or a low-intensity re-warm up (RW) during the half-time period of two soccer matches. Before and after the first half and before the second half, maximal sprint and jump performance were evaluated. Time–motion analysis of the first 15 min of each half was conducted.
    Figure 5: The re-warmup improved not just abstract performance variables, but also possession of the ball during the initial 15 min of both halves in game with active half-time re-warm up (RW) or a passive half-time period (CON) in total and possession of the ball in defending, neutral, and attacking zone (Edholm. 2015).
    Sprint and jump performance were reduced (P < 0.05) by 2.6% and 7.6%, respectively, during the half-time period in CON, whereas sprint performance was maintained and the decrement in jump performance (3.1%; P < 0.05) was lower after RW. No significant interaction for high-intensity running was observed, but less defensive high-intensity running was observed after RW than CON (0.14 ± 0.06 vs 0.22 ± 0.07 km; P < 0.01). Moreover, RW had more possession of the ball in the beginning of the second half. In conclusion, traditional passive half-time rest leads to impaired sprint and jump performance during the initial phase of the second half in professional soccer players whereas a re-warm up effectively attenuates such deteriorations. Less defensive high-intensity running and more ball possession were observed after RW, indicating a game advantage at the onset of the second half. 
  • The effect of high-intensity training on mitochondrial fat oxidation in skeletal muscle and subcutaneous adipose tissue (Larsen. 2015) - High-intensity interval training (HIT) is known to increase mitochondrial content in a similar way as endurance training [60–90% of maximal oxygen uptake (VO2peak)]. Whether HIT increases the mitochondria's ability to oxidize lipids is currently debated.

    Figure 5: At identical levels of palmitoyl carnitine concentrations the lipid oxidation in the subcutaneous fat of the subjects increased significantly after HIT training - this is relevant not just during exercise, but also during dieting, because it signifies that the obese subjects are now having an easier time to access the exuberant energy stores in their subcutaneous body fat stores. The result should be that they are having an easier time losing body fat (Larsen. 2015).
    Scientists from the University of Copenhagen investigated the effect of HIT on mitochondrial fat oxidation in skeletal muscle and adipose tissue. Mitochondrial oxidative phosphorylation (OXPHOS) capacity, mitochondrial substrate sensitivity (Kmapp), and mitochondrial content were measured in skeletal muscle and adipose tissue in healthy overweight subjects before and after 6 weeks of HIT (three times per week at 298 ± 21 W).

    HIT significantly increased VO2peak from 2.9 ± 0.2 to 3.1 ± 0.2 L/min. No differences were seen in maximal fat oxidation in either skeletal muscle or adipose tissue. Kmapp for octanoyl carnitine or palmitoyl carnitine were similar after training in skeletal muscle and adipose tissue.

    Maximal OXPHOS capacity with complex I- and II-linked substrates was increased after training in skeletal muscle but not in adipose tissue.  The scientists conclude: "6 weeks of HIT increased VO2peak. Mitochondrial content and mitochondrial OXPHOS capacity were increased in skeletal muscle, but not in adipose tissue. Furthermore, mitochondrial fat oxidation was not improved in either skeletal muscle or adipose tissue" (Larsen. 2015).
Barefoot or Shod? A Question of Faith & Science: What do scientists and practicioners say?  Find out!
What's your favorite study? The one about increased fatty acid oxidation? That's not really news. While the study by Larsen et al. may be the first to measure it directly in the adipose tissue,  you as a SuppVersity reader should know that HIIT is an effective strategy to increase not just the acute, but also the chronic capacity to oxidize body fat.

My personal favorite is thus the "shoe study" - I mean, the insight that you can significantly reduce your injury risk by switching back and forth between different shoes is a practically highly relevant finding that may also put an end to the "shod or barefoot"-discussion I have addressed in previous articles | Comment on Facebook!
  • Edholm, P., Krustrup, P. and Randers, M. B. (2015), Half-time re-warm up increases performance capacity in male elite soccer players. Scandinavian Journal of Medicine & Science in Sports, 25: e40–e49. doi: 10.1111/sms.12236
  • Habets, B. and van Cingel, R. E. H. (2015), Eccentric exercise training in chronic mid-portion Achilles tendinopathy: A systematic review on different protocols. Scandinavian Journal of Medicine & Science in Sports, 25: 3–15. doi: 10.1111/sms.12208.
  • Larsen, S., Danielsen, J. H., Søndergård, S. D., Søgaard, D., Vigelsoe, A., Dybboe, R., Skaaby, S., Dela, F. and Helge, J. W. (2015), The effect of high-intensity training on mitochondrial fat oxidation in skeletal muscle and subcutaneous adipose tissue. Scandinavian Journal of Medicine & Science in Sports, 25: e59–e69. doi: 10.1111/sms.12252
  • Lavin, K. M., Guenette, J. A., Smoliga, J. M. and Zavorsky, G. S. (2015), Controlled-frequency breath swimming improves swimming performance and running economy. Scandinavian Journal of Medicine & Science in Sports, 25: 16–24. doi: 10.1111/sms.12140.
  • Malisoux, L., Ramesh, J., Mann, R., Seil, R., Urhausen, A. and Theisen, D. (2015), Can parallel use of different running shoes decrease running-related injury risk?. Scandinavian Journal of Medicine & Science in Sports, 25: 110–115. doi: 10.1111/sms.12154.
  • Rosenkilde, M., Reichkendler, M. H., Auerbach, P., Bonne, T. C., Sjödin, A., Ploug, T. and Stallknecht, B. M. (2015), Changes in peak fat oxidation in response to different doses of endurance training. Scandinavian Journal of Medicine & Science in Sports, 25: 41–52. doi: 10.1111/sms.12151