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Muscle Heating in Human Subjects With 915 MHz. Microwave Contact Applicator

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Barbara J. DeLateur, Justus F. Lehmann, Jerry B. Stonebridge, C. Gerald Warren, Arthur W. Guy · 1970

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1970 research proved 915 MHz microwaves create measurable heating effects in human muscle tissue.

Plain English Summary

Summary written for general audiences

This 1970 study examined how 915 MHz microwave radiation heats muscle tissue in human subjects using direct contact applicators. The research explored temperature distribution patterns in muscles during microwave diathermy treatment. This early human exposure study provides baseline data on how microwave frequencies affect tissue heating.

Why This Matters

This study represents crucial early research into how microwave radiation interacts with human tissue at the cellular level. The 915 MHz frequency tested sits squarely in the range used by many modern wireless devices, making these findings directly relevant to today's EMF exposure concerns. What makes this research particularly significant is that it demonstrates measurable biological effects from microwave radiation in living human subjects, not just laboratory models. The reality is that this frequency range can penetrate tissue and create heating effects that go beyond what we might expect from everyday wireless exposures. While this was medical research using intentional heating, it establishes that microwave radiation at these frequencies produces real, measurable biological changes in human muscle tissue.

Figures from the Original Paper

Diagrams extracted from the original research document.

graphPage 2 - Figure 1 - Temperatures in a typical experiment at various depths of tissue resulting from application of microwave with a 9.15 MHz contact applicator.
p. 2 of the original PDF
graphPage 3 - Temperature distribution in all volunteers with ≤1 cm. of subcutaneous fat after 8 minutes of microwave application.
p. 3 of the original PDF
graphPage 4 - Figure 4 - Temperatures in a typical experiment at various depths of tissue resulting from application of microwave with a 915 MHz contact applicator.
p. 4 of the original PDF
chartPage 5 - Temperature distribution in all volunteers with ≥2 cm. of subcutaneous fat after 8 minutes of microwave application (Fig. 6)
p. 5 of the original PDF

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 915 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 915 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. Duration: 20 minutes

Study Details

To evaluate the effectiveness of using a direct contact microwave applicator operating at 915 MHz for muscle heating in human volunteers, with particular focus on temperature control through superficial cooling and the resulting heating patterns in different fat thickness groups.

Selected human volunteers were divided into two groups on the basis of thickness of fat of the anter...

In thin subjects (<1 cm. fat), cooling affected the skin and subcutaneous fat, and to a lesser exten...

Use of superficial cooling with application of microwave diathermy at 915 MHz allows adequate muscle heating without exceeding tolerance levels in the subcutaneous fat. The principal effect of cooling is upon the skin and fat, with little or no effect upon the muscle. An increase in blood flow in the superficial muscle layers provides uniform muscle heating over a period of time, by cooling the superficial layers as the deeper layers of muscle continue to heat with continued application. This mode of application compensates quite well for the subcutaneous fat layer. The heating was most uniform in thin subjects, with an average depth of 2.5 cm. in thinner subjects compared to 2.1 cm. in fatter subjects.

Cite This Study
Barbara J. DeLateur, Justus F. Lehmann, Jerry B. Stonebridge, C. Gerald Warren, Arthur W. Guy (1970). Muscle Heating in Human Subjects With 915 MHz. Microwave Contact Applicator.
Show BibTeX
@article{muscle_heating_in_human_subjects_with_915_mhz_microwave_contact_applicator_g4192,
  author = {Barbara J. DeLateur and Justus F. Lehmann and Jerry B. Stonebridge and C. Gerald Warren and Arthur W. Guy},
  title = {Muscle Heating in Human Subjects With 915 MHz. Microwave Contact Applicator},
  year = {1970},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Researchers used 915 MHz microwave radiation applied directly to human subjects through contact applicators. This frequency is within the range used by many modern wireless communication devices and industrial heating applications.
The study used contact applicators that placed the 915 MHz microwave source directly against the skin. This method was part of medical diathermy research to understand how microwaves penetrate and heat muscle tissue.
Yes, this research demonstrated that 915 MHz microwaves can create measurable temperature increases in human muscle tissue. The study specifically examined temperature distribution patterns to understand how deeply the heating effects penetrated.
This research was conducted to understand microwave diathermy for medical applications. Scientists needed to know how 915 MHz radiation affected tissue temperature and penetration depth for therapeutic heating treatments.
915 MHz falls within the ISM band used by various wireless devices today, including some industrial and medical equipment. While modern cell phones typically use different frequencies, this research shows biological effects are possible in nearby frequency ranges.