Håvard Nygaard

Slow postmeal walking reduces postprandial glycemia in middle-aged women

Postprandial blood glucose concentration is a risk factor for the development of cardiovascular diseases and diabetes, even at states well below hyperglycemic levels. A previous study has shown that postmeal exercise of moderate intensity blunts the blood glucose increase after carbohydrate intake (Høstmark et al. Prev. Med. 42(5): 369-371). The objective of the present study was to examine whether even postmeal slow walking would have a similar effect. Fourteen healthy women aged >50 years participated in 3 experiments in a random crossover design: after a carbohydrate-rich meal, either they were seated (control experiment) or they performed slow postmeal walking for 15 min (W15) or 40 min (W40). Blood glucose concentration was determined prior to the meal (fasting), and at 11 time points throughout each experiment. The W15 trial lowered the blood glucose values during walking and delayed the peak blood glucose value (p = 0.003). In W40, the postmeal blood glucose increase during walking was blunted, the peak glucose value was delayed (p = 0.001), and the incremental area under the 2-h blood glucose curve (IAUC) was reduced (p = 0.014). There was a negative relationship between IAUC and walking time (p = 0.016). The individual reducing effect of walking on IAUC correlated strongly with IAUC on the control day (p < 0.001). We conclude that even slow postmeal walking can reduce the blood glucose response to a carbohydrate-rich meal. The magnitude of this effect seems to be related to the duration of walking and to the magnitude of the postprandial blood glucose response when resting after a carbohydrate-rich meal.

Irisin in Blood Increases Transiently after Single Sessions of Intense Endurance Exercise and Heavy Strength Training

Purpose Irisin is a recently identified exercise-induced hormone that increases energy expenditure, at least in rodents. The main purpose of this study was to test the hypothesis that Irisin increases acutely in blood after singular sessions of intense endurance exercise (END) and heavy strength training (STR). Secondary, we wanted to explore the relationship between body composition and exercise-induced effects on irisin, and the effect of END and STR on muscular expression of the irisin gene FNDC5. Methods Nine moderately trained healthy subjects performed three test days using a randomized and standardized crossover design: one day with 60 minutes of END, one day with 60 minutes of STR, and one day without exercise (CON). Venous blood was sampled over a period of 24h on the exercise days. Results Both END and STR led to transient increases in irisin concentrations in blood, peaking immediately after END and one hour after STR, before gradually returning to baseline. Irisin responses to STR, but not END, showed a consistently strong negative correlation with proportions of lean body mass. Neither END nor STR affected expression of FNDC5, measured 4h after training sessions, though both protocols led to pronounced increases in PGC-1α expression, which is involved in transcriptional control of FNDC5. Conclusion The results strongly suggest that single sessions of intense endurance exercise and heavy strength training lead to transient increases in irisin concentrations in blood. This was not accompanied by increased FNDC5 expression, measured 4h post-exercise. The results suggest that irisin responses to resistance exercise are higher in individuals with lower proportions of lean body mass.

Effects of 12 weeks of block periodization on performance and performance indices in well-trained cyclists.

The purpose of this study was to compare the effects of two different methods of organizing endurance training in trained cyclists during a 12‐week preparation period. One group of cyclists performed block periodization (BP; n = 8), wherein every fourth week constituted five sessions of high‐intensity aerobic training (HIT), followed by 3 weeks of one HIT session. Another group performed a more traditional organization (TRAD; n = 7), with 12 weeks of two weekly HIT sessions. The HIT was interspersed with low‐intensity training (LIT) so that similar total volumes of both HIT and LIT were performed in the two groups. BP achieved a larger relative improvement in VO2max than TRAD (8.8 ± 5.9% vs 3.7 ± 2.9%, respectively, P < 0.05) and a tendency toward larger increase in power output at 2 mmol/L [la−] (22 ± 14% vs 10 ± 7%, respectively, P = 0.054). Mean effect size (ES) of the relative improvement in VO2max, power output at 2 mmol/L [la−], hemoglobin mass, and mean power output during 40‐min all‐out trial revealed moderate superior effects of BP compared with TRAD training (ES range was 0.62–1.12). The present study suggests that BP of endurance training has superior effects on several endurance and performance indices compared with TRAD.

Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training

Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSApeak, potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women.

Reliable determination of training-induced alterations in muscle fiber composition in human skeletal muscle using quantitative polymerase chain reaction

Determination of muscle fiber composition in human skeletal muscle biopsies is often performed using immunohistochemistry, a method that tends to be both time consuming, technically challenging, and complicated by limited availability of tissue. Here, we introduce quantitative reverse transcriptase polymerase chain reaction (qRT‐PCR)‐based Gene‐family profiling (GeneFam) of myosin heavy chain (MyHC) mRNA expression as a high‐throughput, sensitive, and reliable alternative. We show that GeneFam and immunohistochemistry result in similar disclosures of alterations in muscle fiber composition in biopsies from musculus vastus lateralis and musculus biceps brachii of previously untrained young women after 12 weeks of progressive strength training. The adaptations were evident as (a) consistent increases in MyHC2A abundance; (b) consistent decreases in MyHC2X abundance; and (c) consistently stable MyHC1 abundance, and were not found using traditional reference gene‐based qRT‐PCR analyses. Furthermore, muscle fiber composition found using each of the two approaches was correlated with each other (r = 0.50, 0.74, and 0.78 for MyHC1, A, and X, respectively), suggesting that GeneFam may be suitable for ranking of individual muscle phenotype, particularly for MyHC2 fibers. In summary, GeneFam of MyHC mRNA resulted in reliable assessment of alterations in muscle fiber composition in skeletal muscle of previously untrained women after 12 weeks of strength training.

Strength and hypertrophy with resistance training: chasing a hormonal ghost

Professor Phillips (2011) is correct in stating that in our recent paper (Rønnestad et al. 2011), we report in our abstract that “...only L + A achieved increase in CSA at the part of the arm Xexors with largest cross sectional area (p < 0.001), while no changes occurred in A”. However, when he claims that it is misleading that we do not mention in the abstract that both L + A and A increased cross sectional area (CSA) at the two sites with the smallest CSA, we feel that this has been taken out of context. In the previous sentence quoted by Professor Phillips, we clearly state that: “Both A and L + A increased in...muscle volume of the elbow Xexors”, thereby pointing towards an increased CSA at some measured sections of the elbow Xexors also in A. Since only the major results could be presented in the abstract, and we had presented the changes in muscle volume from the measured sections, we felt that it was unnecessary to explicitly mention that L + A achieved increased CSA at all four measured sites of the elbow Xexors (including the two largest sites), while A only achieved increased CSA at the two smallest sites. However, these results are of course mentioned in the results section. Furthermore, Professor Phillips claims that incomplete statistical analyses were performed since it was not mentioned explicitly that there was no diVerence between groups in changes in muscle volume or CSA at the measured sites. However, in the section on statistics we clearly described the statistical procedures we used to test for diVerences in relative changes from preto post for each of these measurements. It is correct that we did not explicitly mention that there was no diVerence between groups in these measurements, and the reason was simply that there is a practice in the literature that if no diVerence is stated, then there is no diVerence. In the same way, we did mention explicitly that there were diVerences between L + A and A in relative gains in 1RM and a tendency towards a diVerence in peak power output at 60% of 1RM. We did not Wnd any statistical signiWcant diVerences between L + A and A in any of the four measured CSA sections or in muscle volume (as calculated based on the four measured sites) and we did not state in our paper that there was a signiWcant diVerence between L + A and A in these measurements. In fact, at the site of the elbow Xexors with the largest CSA, there was a tendency towards a larger increase in CSA in L + A compared to A (p = 0.08), but in an attempt to be conservative in our presentation of the results; we did not mention this in the paper. Indeed, we reported that L + A only achieved a signiWcant increase in CSA at the two sites where the elbow Xexors had the largest CSA, while A had no statistical signiWcant increase at these sites. Based on these Wndings, it is not strange that there was not a statistical signiWcant diVerence between L + A and A in changes in muscle volume. We do not think that the A arm got longer as Prof. Phillips has implied. Furthermore, we want to emphasize that in the Methods section we stated that the muscle volume was calculated from the four measured sections and, thus does not reXect the total muscle volume of the elbow Xexors. Professor Phillips cited the following from our abstract: “L + A had...favourable muscle adaptations in elbow Xexors compared to A (p < 0.05)” and he follows up this quote Communicated by Susan A. Ward.

10 weeks of heavy strength training improves performance-related measurements in elite cyclists

ABSTRACT Elite cyclists have often a limited period of time available during their short preparation phase to focus on development of maximal strength; therefore, the purpose of the present study was to investigate the effect of 10-week heavy strength training on lean lower-body mass, leg strength, determinants of cycling performance and cycling performance in elite cyclists. Twelve cyclists performed heavy strength training and normal endurance training (E&S) while 8 other cyclists performed normal endurance training only (E). Following the intervention period E&S had a larger increase in maximal isometric half squat, mean power output during a 30-s Wingate sprint (P < 0.05) and a tendency towards larger improvement in power output at 4 mmol ∙ L−1 [la−] than E (P = 0.068). There were no significant difference between E&S and E in changes in 40-min all-out trial (4 ± 6% vs. −1 ± 6%, respectively, P = 0.13). These beneficial effects may encourage elite cyclists to perform heavy strength training and the short period of only 10 weeks should make it executable even in the compressed training and competition schedule of elite cyclists.

Long-term effects of daily postprandial physical activity on blood glucose: a randomized controlled trial

Previous studies have shown that a bout of moderate or light postprandial physical activity effectively blunts the postprandial increase in blood glucose. The objective of this study was to test whether regular light postprandial physical activity can improve glycemia in persons with hyperglycemia or with a high risk of hyperglycemia. We randomized 56 participants to an intervention or a control group. They were diagnosed as hyperglycemic, not using antidiabetics, or were categorized as high-risk individuals for type 2 diabetes. The intervention group was instructed to undertake a minimum 30 min of daily light physical activity, starting a maximum of 30 min after a meal in addition to their usual physical activity for 12 weeks. The control group maintained their usual lifestyle. Blood samples were taken pre- and post-test. Forty participants completed the study and are included in the results. The self-reported increase in daily physical activity from before to within the study period was higher in the intervention group compared with control (41 ± 25 vs. 2 ± 16 min, p < 0.001). Activity diaries and accelerometer recordings supported this observation. The activity in the intervention group started earlier after the last meal compared with control (30 ± 13 vs. 100 ± 57 min, p = 0.001). There were no within- or between-group differences in any glycemic variable from pre- to post-test. In conclusion, the present study does not seem to support the notion that regular light postprandial physical activity improves blood glucose in the long term in persons with hyperglycemia or with high risk of hyperglycemia.