RESEARCH: Studies reviewed this week: 29 March 2021 to 4 April 2021

NUTRITION: Exogenous ketosis impacts neither performance nor muscle glycogen breakdown in prolonged endurance exercise

I've shared a couple of studies before (here and here) about ketone use and sports performance. Both of these showed that there was no benefit for cycling or running performance. In this study the authors set out to see if ketone ingestion spared glycogen: "we investigated whether acute exogenous ketosis by oral ketone ester (KE) intake early in a simulated cycling race can induce transient glycogen sparing by glycolytic inhibition, thereby increasing glycogen availability in the final phase of the event".

The protocol was a simulation of a cycling race:

A simulated cycling race (RACE), which consisted of 3-h intermittent cycling (IMT180'), a 15-min time trial (TT15'), and a maximal sprint (SPRINT). During RACE, subjects received 60 g carbohydrates/h combined with three boluses (25, 20, and 20 g) (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) or a control drink (CON) at 60 and 20 min before and at 30 min during RACE.

The authors found that:

Exogenous ketosis produced by oral ketone ester ingestion during the early phase of prolonged endurance exercise and against the background of adequate carbohydrate intake neither causes muscle glycogen sparing nor improves performance in the final stage of the event.

PRACTICAL TAKEAWAY - ketones still haven't been proven to improve performance.

ALTITUDE: Regulation of satellite cells by exercise in hypoxic conditions

In this study the authors set out to "investigate in vivo the adaptations of satellite cell induced by exercise performed in acute or chronic hypoxic conditions and their contribution to muscle remodeling and hypertrophy". The important distinction they made between acute and chronic conditions could help to inform altitude training protocols. The authors found that:

Satellite cell activation and proliferation seem to be enabled after acute hypoxic exercise via regulations induced by myogenic regulatory factors.

but that:

Chronic exposure to hypoxia downregulates myogenesis despite the maintenance of physical activity. This impaired myogenesis might be induced by excessive oxidative stress and proteolysis.

PRACTICAL TAKEAWAY - while the study notes that more research is needed, it does provide an idea that chronic periods at altitude may be detrimental indicating the need for caution in planning long-duration training camps at altitude.

TRAINING: Superior Physiological Adaptations After a Microcycle of Short Intervals Versus Long Intervals in Cyclists

I shared this study on short intervals by Ronnestad previously. In the takeaways from that study I also some of the potential conflicting advice that suggests that longer intervals are required for increasing VO2 Max. While I still believe there are places for training both shorter and longer intervals, I found this study with a very specific intervention for short intervals to be fascinating.

The protocol was for a week-long microcycle of training compared:

A 1-week high-intensity aerobic-training shock microcycle composed of either 5 short-interval sessions (SI; n = 9, 5 series with 12 × 30-s work intervals interspersed with 15-s recovery and 3-min recovery between series) or 5 long-interval sessions (LI; n = 8, 6 series of 5-min work intervals with 2.5-min recovery between series).

The results showed that:

From pretraining to posttraining, SI achieved a larger improvement than LI in maximal oxygen uptake (5.7%; 95% confidence interval, 1.3–10.3; P = .015) and power output at a blood lactate concentration of 4 mmol/L.

PRACTICAL TAKEAWAY - using a week-long intervention of short, high-intensity intervals can produce greater endurance performance development than an intervention with longer intervals.

TRAINING: The Effect of Training Status on Adaptations to 11 Weeks of Block Periodization Training

I believe that a block periodisation training plan can be beneficial and useful for certain athletes and at certain times in a training cycle. This study looked at strength training with the intention "to investigate the effect of training status on performance outcomes resulting from 11 weeks of BP training". This is particularly interesting because it helps to identify who might benefit most from a block periodisation training plan.

The results showed that:

All subjects showed statistically significant improvements in 0 kg static jump (SJ), 0 kg countermovement jump (CMJ), 20 kg SJ, and 20 kg CMJ.
Statistically significant between group differences were noted for both 20 kg SJ and 20 kg CMJ with the strong group statistically greater jump heights than the weak group.

PRACTICAL TAKEAWAY - block periodisation may be a more effective training distribution for well-trained athletes.

NUTRITION: Administration of Caffeine in Alternate Forms

Caffeine is a known ergogenic aid and one of the supplements every endurance athlete should consider. This study looked into the various ways of ingesting caffeine and their individual aspects of absorbtion and effectiveness. Key points from the review include:

Caffeinated chewing gum is absorbed quicker through the buccal mucosa compared with capsule delivery and absorption in the gut, although total caffeine absorption over time is not different. Rapid absorption may be important in many sporting situations. Caffeinated chewing gum improved endurance cycling performance, and there is limited evidence that repeated sprint cycling and power production may also be improved.
Mouth rinsing with caffeine may stimulate nerves with direct links to the brain, in addition to caffeine absorption in the mouth. However, caffeine mouth rinsing has not been shown to have significant effects on cognitive performance. Delivering caffeine with mouth rinsing improved short-duration, high-intensity, repeated sprinting in normal and depleted glycogen states, while the majority of the literature indicates no ergogenic effect on aerobic exercise performance, and resistance exercise has not been adequately studied.
Caffeinated aerosol mouth and nasal sprays may stimulate nerves with direct brain connections and enter the blood via mucosal and pulmonary absorption, although little support exists for caffeine delivered in this manner.

PRACTICAL TAKEAWAY - capsules and caffeinated chewing gum may be the optimal means of caffeine delivery.

NUTRITION: Primary, Secondary, and Tertiary Effects of Carbohydrate Ingestion During Exercise

This is a useful paper in understanding the effects of carbohydrate ingestion. The paper considers three points during carbohydrate ingestion:

The primary stage is detection of ingested carbohydrate by receptors in the oral cavity and on the tongue that activate reward and other centers in the brain leading to insulin secretion.
After digestion, the secondary stage is the transport of monosaccharides from the small intestine into the systemic circulation. The passage of these monosaccharides is facilitated by the presence of various transport proteins.
The tertiary phase can be defned as the efects that CHO exerts when it becomes available in the systemic circulation. Maintaining CHO availability (and thereby preventing hypoglycaemia, defned as blood glucose concentrations less than 3.5 mmol/L) during exercise is important for both central (brain) as well as peripheral (muscle) function in maintaining carbohydrate oxidation to sustain exercise performance.

PRACTICAL TAKEAWAY - understanding the different effects of carbohydrate ingestion can help to determine the optimal fueling for sports performance.

No comments: