April Journal Review

Dr. Blake Middleton Article, Blog, Reviews Leave a Comment

I know I haven’t put out a review in a few months. Honestly the research for endurance athletes is limited in the journals recently. To prevent further delay, here are a few studies that I have collected and appear pertinent. Two of the 3 studies contain great info as summer nears which also means training and racing in the heat. The 3rd review is a reminder that as we quantify our work there is a need to control all variables. Hope you all enjoy!

Temperature Performance Benefits after Heat Exposure

26 well-trained male and female middle distance runners participated in the study. They all had been running >2 years and regularly complete 10-20 hours of training per week. All completed a 4 week block of baseline training and then were divided into 1 of 3 groups: 1) Regular Training, 2) Heat Training, 3) Heat + hypoxic training for 3 weeks. Then 3 more weeks of the baseline training was completed in all groups. Testing occurred prior to the 3 week test and then throughout the post 3 week baseline training.

Each group completed 3 – 90 minute treadmill sessions per week consisting of 2 interval and 1 aerobic based run during the study. The heat sessions were done at 90 degrees compared to 55 degrees for the control group. The main outcome testing was a 3K (just under 2 mi) running time trial. The heat group performed the best with results. The results also through the 3 weeks post training/testing period with an average time improvement of 3.3%.

APPLICATION: It may be beneficial to turn up the heat when trying to improve your performance. I see this beneficial if you have already maxed out your available time to get in workout sessions. When time crunched,  it may be wise to set up your bike trainer or treadmill in the garage or waiting till the warmer parts of the day to get in training (with plenty of hydration). Perhaps a sauna session before your workout would have some effect as well. The interesting  takeaway is that after just 3 weeks of heat training the positive effects on performance lasted another 3 weeks.


Impact of Acute Dietary Manipulations on DXA and BIA Body Composition Estimates

In this study, 48 participants were provided with two separate 1 day diets (high carb and low carb). For each diet, body composition was assessed the morning after an overnight fast, the afternoon after eating, and the following morning after a second overnight fast.

Results revealed that acute food ingestion, regardless of diet, altered body composition testing. DXA total and regional lean soft tissue mass increased 1.7% and 3% on average respectively during afternoon testing. These results are compared to the fasting testing from that morning. The largest discrepancy was 4.5% and 9% respectively in one participant. There was also a decrease in trunk fat mass of 3% on average. These results returned to baseline after a 2nd night of fasting. Similar changes were seen when using bioelectrical impedance analysis devices (the hand held or scale devices that measure body fat).

Application: This one is simple. Ensure to control as many variables as possible when performing body composition testing. I typically recommend 3 things prior to body composition testing.

  1. No exercise the prior 24 hours (get your workout in early the day before)
  2. Ingesting at least 64 ounces of water the day prior and consuming your normal diet
  3. Not eating or drinking at least 8 hours prior to testing.

If you follow these simple rules your comp testing will be the most accurate from one session to the next. I recommend testing every 3-4 months in general to track changes. This time frame may be different depending on training or diet goals.


Running Performance in the Heat is improved by similar Magnitude with Pre-Exercise Cold Water Immersion and Mid-Exercise Cold Water Spray

9 male runners studied had been training regularly in the heat.  This included at least 4 outdoor training session a week for four weeks in the summer. These runners held 5K times between 18 and 22 minutes. The study evaluated each runner under 3 different conditions running a 5K at 91 degrees fairenheight and 34% humidity. The interventions included a pre-run cold water immersion, mid-run face cold water spray, and a run with no intervention.

The cold water immersion condition included sitting in a cold water bath of 74 degrees for 30 minutes. Included was 20 minutes between immersion and run to allow set-up and warm-up time. During the face spray run, each participant was sprayed 3 times at each kilometer with 72 degree water.

Results revealed a 2.7% improvement in running time in both the immersion (24:30) and face spray (24:36) groups compared to the no intervention run (25:12). Overall running times were slower (compared to the 18-22 min best) due to the treadmill used. The treadmill used is found on average to have running times increased by 20%.

Application: This study highlights a pair of underutilized aids for exercising in hot conditions. Other methods studied elsewhere include ingesting slurry type drinks along with cooling packs and vests. It is likely the spraying would be beneficial in longer efforts. Other studies suggest water immersion is short lived and benefits decrease after 20-30 minutes of exercise. This is when the body core temperature increases back near baseline. However, the facial spray may be less beneficial in more humid conditions due to lack of evaporation. Combing cold water immersion, face sprays, cooling clothing and packs, along with ingesting slurry drinks would likely have the greatest impact in warmer and humid conditions.

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